Gas/MPG's - What can we do?

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Gas/MPG's - What can we do?

Postby Ilya » Sun Apr 03, 2011 10:03 am

I didn't see a thread like this around so I decided to make it.

As we know, the M (35 or 45) isn't exactly known for it's gas mileage.

Here are some things that you can do to help yourself achieve better gas milage:

*** Note: Some of these may be minimal, but added together as a whole it will help - at least it has on past cars I've owned ***
  • Clean all engine bay ground points
  • Clean throttle body (when you remove the rubber/plastic intake pieces and you get to the butterfly plate in the throttle body...clean that area. This did wonders on the VQ30DE in the Maxima that I owned previously.)
  • Run a fuel system cleaner every 10k or so (such as Gumout, Chevron Techron, Seafoam, etc.). Running them more often is usually a waste of money says Consumer Reports.
  • Change your PCV valve from time to time. I usually do it every 15k. It's not a terribly difficult job and I might make a HowTo thread on how to do it next time I do it. It's also a really cheap part.
  • Keep your oil clean
  • Keep your air filters clean
  • Keep your tires properly inflated (should be around 33psi on the M if I recall)
  • Make sure your spark plugs are in good health and properly spaced at .044mm I believe (example; if you have 80kmi on your car you should probably think about changing them)
  • Don't drive with a heavy foot
Now here is where I have some questions. Is there any mods that people can do to help increase MPG's as well? I believe I read somewhere that certain exhaust parts, intake spacers, etc. can help. Do we know how much they help? Is it 1 or 2 MPG's? Or more?

If anyone finds any discrepancies in my suggestions above or wants to add something, post in here. This might be a good resource for our members as gas gets more expensive by the month.


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Re: Gas/MPG's - What can we do?

Postby a.blanco0905 » Sun Apr 03, 2011 10:16 am

An exhaust system helps the engine breathe easier as the back pressure of the gases exiting the exhaust is significantly reduced. For the most part Cold Air Intakes help, especially the K&N ones... regular K&N filters (OEM replacements) Help as well... if you dont want to go full exhaust route you could get flowmaster mufflers and that helps too... Keeping up with basic and regular maintenance, as you basically stated above is the ultimate no brainer tho... tuning your car helps as well.

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Re: Gas/MPG's - What can we do?

Postby Ilya » Sun Apr 03, 2011 10:18 am

For those people who'd like to get an exhaust but not sacrifice noise level, what is the most OEM like exhaust in terms of noise output?

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Re: Gas/MPG's - What can we do?

Postby white_wolf » Sun Apr 03, 2011 10:38 am

If you want the most OEM like exhaust note, just keep the stock resonators. I went to a friend's shop and had borlas outfitted on mine(pics to follow when I finish a few other mods). My friend thought it would be loud, so he suggested I keep the stock resonators on..... :facepalm: it's still kinda quiet. I'm going to install shorter/smaller resonators later this month (video to follow).

I know the exhaust should have increased my gas mileage... but I installed a spacer a few days after getting the exhaust, so I can't attest to an increase with my exhaust.

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Re: Gas/MPG's - What can we do?

Postby Ilya » Sun Apr 03, 2011 10:41 am

Let us know how your MPG's are after you've had your spacer/exhaust running for a little while.

Right now, I average about 18.5 mixed drive (with a somewhat heavy foot). If I baby it, I can get it to about 23. On the highway, on my way to FL 3 weeks ago, I was averaging about 88mph and was doing 20.1mpg. That's a stock car with very good maintenance records (although I haven't done the ground points or cleaned the throttle body).

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Re: Gas/MPG's - What can we do?

Postby a.blanco0905 » Sun Apr 03, 2011 10:58 am

I really dont know what my "mixed" avg is, but I know this much... on my M45 straight up city driving I avg about 14.5 MPG and on the highway driving decently 70-75 MPH I do from 19 to 21 MPG... 80-85 MPH and it goes down to 18-19 MPG...

Stillen exhaust sounds pretty low & decent btw...

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Re: Gas/MPG's - What can we do?

Postby EniGmA1987 » Sun Apr 03, 2011 12:54 pm

IlyaKol wrote:For those people who'd like to get an exhaust but not sacrifice noise level, what is the most OEM like exhaust in terms of noise output?
HKS Legamax from what I see posted about it.

IlyaKol wrote:[*]Clean throttle body (when you remove the rubber/plastic intake pieces and you get to the butterfly plate in the throttle body...clean that area. This did wonders on the VQ30DE in the Maxima that I owned previously.)
I thought we werent supposed to touch the throttle body as it has a certain fluid or treatment or something on it that can cause problems if you mess it up? And its expensive to get fixed.





I dont think adding a spacer improves MPG, wouldnt it worsen MPG? The car keeps a specific air to fuel ratio, if you add a spacer in so the engine gets more air, then the ECU puts more fuel in to maintain the ratio. At least thats how I thought cars worked. So more air = more fuel use.

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Re: Gas/MPG's - What can we do?

Postby white_wolf » Sun Apr 03, 2011 2:08 pm

EniGmA1987 wrote:I dont think adding a spacer improves MPG, wouldnt it worsen MPG? The car keeps a specific air to fuel ratio, if you add a spacer in so the engine gets more air, then the ECU puts more fuel in to maintain the ratio. At least thats how I thought cars worked. So more air = more fuel use.
Adding a spacer should indeed (at least on paper and in theory) increase MPG.

Increasing air intake improves the air to fuel ratio. With sufficient air in the combustion chamber, it helps burn up every drop of fuel being used.

I like to think of it like this:
Cars reallly don't "breathe" as well as they should straight out of the factory; meaning the manufacturers restrict air intake...via the air intake. I'm not sure of exact reasons for this, but a lot of people seem to point to noise output; manufacturers believe that the average consumer want their new cars to be as silent as possible. This means that the intake of air is sacrificed for the sake of sound output(among other things).

*note: I'm totally going to make up numbers for the sake of illustration*
Say the "perfect" air to fuel ratio is 5:3 (5 units of air to 3 units of fuel) making X-amount of energy sufficient to propel the car. Since the factory restricts air intake... lets say to 3 units; the car still has to produce X-amount of energy... and to offset the lack of air, it has to use more fuel... lets say 2 units more. This would mean under factory settings the air to fuel ratio is 2:5... more gas is used.

I could be completely off with my logic of how air to fuel ratio actually works in relation to a car... However, my previous car was a '98 Prelude. Over the course of 3 months (all stock) I tracked an average of 19mpg(mixed driving). By the time I sold the car, I tracked an average of 25mpg(mixed driving) with the addition of intake, headers, and exhaust.

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Re: Gas/MPG's - What can we do?

Postby antzrus » Sun Apr 03, 2011 2:35 pm


An M or a Prius? You obviously made your well informed decision. You are on this site; an M enthusiast site. What's the problem?

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Re: Gas/MPG's - What can we do?

Postby Ilya » Sun Apr 03, 2011 5:32 pm

EniGmA1987 wrote:
IlyaKol wrote:For those people who'd like to get an exhaust but not sacrifice noise level, what is the most OEM like exhaust in terms of noise output?
HKS Legamax from what I see posted about it.

IlyaKol wrote:[*]Clean throttle body (when you remove the rubber/plastic intake pieces and you get to the butterfly plate in the throttle body...clean that area. This did wonders on the VQ30DE in the Maxima that I owned previously.)
I thought we werent supposed to touch the throttle body as it has a certain fluid or treatment or something on it that can cause problems if you mess it up? And its expensive to get fixed.
I'll have to look into the HKS. I'm toying with the idea because I live in NY and I give my current exhaust another year or two before it'll start to deteriorate thanks to our DOT using salt instead of sand.

Do you have any videos by any chance? I found some for other cars, but not an M.

EDIT: I found videos of the exhaust on an FX35, would it be the same for our car?

Reving: http://www.youtube.com/watch?v=B1c0q8AtWe8
Drive Off: http://www.youtube.com/watch?v=y6_jHXMrAhM
------------------------

About the throttle body. I think that's maybe if you remove it? I've cleaned it a little by just opening the throttle body plate (butterfly plate) and taking a brush soaked in throttle body cleaner to it. I dont' see any other fluids, etc. It does look like it's a sealed unit otherwise so if you REMOVE it then you might have issues. I used to remove it on the Maxima cause all it had was a gasket...made things much easier.

On the M, just put a towel under the TB, spray it with TB cleaner and go to town on the butterfly plate and where the butterfly plate meets the TB opening (that entire rim). And behind it.
antzrus wrote:
An M or a Prius? You obviously made your well informed decision. You are on this site; an M enthusiast site. What's the problem?
lol. There is no reason why we shouldn't try and get as much bang for the buck as we can. I love my car whether it gets 15mpg or 25mpg, but I'd love it even more if I got 25 lol.

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Re: Gas/MPG's - What can we do?

Postby antzrus » Sun Apr 03, 2011 6:39 pm

IlyaKol wrote:
antzrus wrote:
An M or a Prius? You obviously made your well informed decision. You are on this site; an M enthusiast site. What's the problem?
lol. There is no reason why we shouldn't try and get as much bang for the buck as we can. I love my car whether it gets 15mpg or 25mpg, but I'd love it even more if I got 25 lol.
Before buying my M, I lurked on these (M, Acura RL, yeah-Prius too etc.) car sites for about x2 years. I am environmentally conscious and I love good gas mileage as much as the next guy. But over the years the M offered something impalpable that I felt in my gut and I had to have one. On these forums gas mileage was never a part of it as so well evidenced by those who bought/leased and complained endlessly and bitterly about the mileage.

Since when does a "luxury sports sedan" hint at good mileage? Herein is one of my favorite rants: If you can't afford a "luxury sports sedan" then wait a few years, work hard, raise your kids, throw away the credit cards and pay cash and then when you can do it; do it!

I had to wait until I was 60 y/o. Delay of gratification builds character... Image

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Re: Gas/MPG's - What can we do?

Postby white_wolf » Mon Apr 04, 2011 3:17 am

antzrus wrote:
An M or a Prius? You obviously made your well informed decision. You are on this site; an M enthusiast site. What's the problem?
There is no problem, I don't see anyone complaining. What I see is people trying to get the most out of their cars... like any other car enthusiast would.

I'm pretty sure everyone who owns a M looking at this thread is hoping to gain a few more MPG... not having grand delusions of reaching econo-box MPG status.

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Re: Gas/MPG's - What can we do?

Postby bbs350z » Mon Apr 04, 2011 1:28 pm

+1 white wolf. antz its not that were complaining, but more so that were seeking a way to extract more mpg's from our car. id like to get slightly better gas mileage. id also like my gf's tits to be a little bigger too. i knew they were small titties getting into the relationship, just as i knew gas mileage wasnt spectacular when i got this car, but theres room for improvement, and i see nothing wrong with seeking new ways to do that. so if i can save a few dollars by getting further while saving money (not for the tits) then im all for it. we all knew what we were getting into when we bought the car, sometimes a little bitching is required to find a solution, lets keep an open mind around here

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Re: Gas/MPG's - What can we do?

Postby mcrews » Mon Apr 04, 2011 4:52 pm

Hate to be the bringer of bad news, but most of the comments will not improve mileage.
NOTE: before you just start to say something, go to "ecomodder.com" THey have a list of "65 things you can do to improve mpg". click on it, read it, look at the proof, look at the sources.
THis is a serious site if you really want to improve mpg
1. If you did not run a "a-b-a" or at least an 'a-b' test when you installed a part, you can't honestly add to the conversation.( how something feels doesnt count.)
A-B-A Testing: Drive car for 15 minutes before, take a run on a fixed distance (7-15 miles), run at a set speed(50-65mph), run up and back w/ out the modd to establish a base MPG, then immediately install the mod and do the run up and back. You now will be able to factually state if the mod helps your vehicle.
2. CAI will not/can not improve MPG. Period. Warm air improves. More hp does not improve mpg.(see ecomodder)
3. Runv Nitro in your tires. Nitro does not fluctuare with road heat. so you are at the correct psi all the time. Don't leave you tires at 33psi. Go to 39-41psi. That's what i run daily and when I'm on the road longer than 2 hrs, I run by Radial Tire Store in Sacramento and go to 46psi. (see Ecomodder.com before making comments)
4. THe key to high mpg is low rpm at cruise speeds. THe 02 Q45 is blessed w a 2.76 rear ratio, the 03-06 and all Ms are 3.XX(not sure the exact gear.) THe recommended tire on the 02Q45 Sport is 245/45/18 on the 18x7.5 rfactory rim. I run a 255/45/18. At 62mph I am at 1824rpm.
5.Taller tires does not mean go uot and get 20 and 22 rims. each pound you add is really 4lbs when it is spinning AND the more wieght you put on the uotside effects the enitire suspension. At the same time if the new rim and tire is slightly taller and wieghts 4 lbs less, the you have removed almost 50lbs from the moving wieght.
5. the TCM(TRANY BRAIN) adjusts to your driving style. the harder you drive the less mpg you will get, even when you try to drive easy on one trip. THe TCM is already trained. I will tell you that I drive for mpg so my tcm IS tuned to get good mpg.
6. I always like hearing talk of the 'restrictive intake' and the "restrictive exhaust". come on. 4.5 liters = 273 cubic inches. you've got 340hp!!! and the 3.5 and 3.7 are pushing 300??
THese engines are finely tuned. Yes, there are marginal gains at he top of the curves on hp, but hp does not equate to more mpgs.
7. Underboby panels. the tubulance created by a ruogh underside can affect the drag by as much as 30%. So keep the stock panels under there.
audi 2011
Image

8. when your on the road keep tthe mpg screen on. "Play beat the mpg"
9. Ecomodder will tell you that the best mod for better mpg is to "adjust the NUT behind the wheel"
10. Finally, since no two drivers or their cars are the same OR the roads and speeds the drive, it really doesnot make any sense to say "I get 17mpg on a fillup or on my screen." There isn't any practical discussion that can take place. But if you say, "I get 20mpg at 65mph over a set disctance", then you can have a conversation about the difference that cause it. I don't check my mileage around town because I know it will suck. But I bust my but to get the best possible mpg when I 'm on the road, because that's where I can really make a difference.
I consistantly get 27+mpg on road trips.

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Re: Gas/MPG's - What can we do?

Postby mcrews » Mon Apr 04, 2011 5:18 pm

Before buying my M, I lurked on these (M, Acura RL, yeah-Prius too etc.) car sites for about x2 years. I am environmentally conscious and I love good gas mileage as much as the next guy. But over the years the M offered something impalpable that I felt in my gut and I had to have one. On these forums gas mileage was never a part of it as so well evidenced by those who bought/leased and complained endlessly and bitterly about the mileage.

Since when does a "luxury sports sedan" hint at good mileage? Herein is one of my favorite rants: If you can't afford a "luxury sports sedan" then wait a few years, work hard, raise your kids, throw away the credit cards and pay cash and then when you can do it; do it!

I had to wait until I was 60 y/o. Delay of gratification builds character... Image
[/quote]

amen! :yesnod :mike

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Re: Gas/MPG's - What can we do?

Postby cruzad3r » Mon Apr 04, 2011 5:23 pm

27+MPG on your Q45 is frikin redonkulous!

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Re: Gas/MPG's - What can we do?

Postby marosari00 » Mon Apr 04, 2011 5:40 pm

mcrews wrote:Before buying my M, I lurked on these (M, Acura RL, yeah-Prius too etc.) car sites for about x2 years. I am environmentally conscious and I love good gas mileage as much as the next guy. But over the years the M offered something impalpable that I felt in my gut and I had to have one. On these forums gas mileage was never a part of it as so well evidenced by those who bought/leased and complained endlessly and bitterly about the mileage.

Since when does a "luxury sports sedan" hint at good mileage? Herein is one of my favorite rants: If you can't afford a "luxury sports sedan" then wait a few years, work hard, raise your kids, throw away the credit cards and pay cash and then when you can do it; do it!

I had to wait until I was 60 y/o. Delay of gratification builds character... Image
amen! :yesnod :mike[/quote]

Totally agree.... :dblthumb:

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Re: Gas/MPG's - What can we do?

Postby antzrus » Mon Apr 04, 2011 6:20 pm

bbs350z wrote:+1 white wolf. antz its not that were complaining, but more so that were seeking a way to extract more mpg's from our car. id like to get slightly better gas mileage. id also like my gf's tits to be a little bigger too. i knew they were small titties getting into the relationship, just as i knew gas mileage wasnt spectacular when i got this car, but theres room for improvement, and i see nothing wrong with seeking new ways to do that. so if i can save a few dollars by getting further while saving money (not for the tits) then im all for it. we all knew what we were getting into when we bought the car, sometimes a little bitching is required to find a solution, lets keep an open mind around here
Well, when you put it that way it does make a lot more sense... :rotflmao

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Re: Gas/MPG's - What can we do?

Postby cruzad3r » Mon Apr 04, 2011 6:50 pm

marosari00 wrote:
mcrews wrote:Before buying my M, I lurked on these (M, Acura RL, yeah-Prius too etc.) car sites for about x2 years. I am environmentally conscious and I love good gas mileage as much as the next guy. But over the years the M offered something impalpable that I felt in my gut and I had to have one. On these forums gas mileage was never a part of it as so well evidenced by those who bought/leased and complained endlessly and bitterly about the mileage.

Since when does a "luxury sports sedan" hint at good mileage? Herein is one of my favorite rants: If you can't afford a "luxury sports sedan" then wait a few years, work hard, raise your kids, throw away the credit cards and pay cash and then when you can do it; do it!

I had to wait until I was 60 y/o. Delay of gratification builds character... Image
amen! :yesnod :mike
Totally agree.... :dblthumb:[/quote]

I don't agree

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Re: Gas/MPG's - What can we do?

Postby EniGmA1987 » Mon Apr 04, 2011 7:00 pm

mcrews wrote:THe 02 Q45 is blessed w a 2.76 rear ratio, the 03-06 and all Ms are 3.XX(not sure the exact gear.)
M45 = 3.39
M35(s) = 3.54 I think
M35x = 3.69



The lower your ratio, the lower your RPMs for a given speed.

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Re: Gas/MPG's - What can we do?

Postby antzrus » Mon Apr 04, 2011 7:00 pm

cruzad3r wrote:
I don't agree

Well, I do; neener, neener! Image

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Re: Gas/MPG's - What can we do?

Postby bbs350z » Mon Apr 04, 2011 7:02 pm

lol^ *pokes gf's bewbee*

mccrews, as im sure your aware, the m35x (5 speed) cruise at 70mph is roughly 3k rpm's. thirsty mother. however i can attest to gaining 1.1 mpg average over 3 tanks (full to empty) with the spacer. and an average of 2.1mpg with my intake + spacer over an additional 3 tankfulls (i took note- and these drives were merely identical every tankful). so while they may not have created power or magical mpg's, they certainly made the motor work more efficiently, and free'd up some power in the process. and while hot air has more velocity, cold air is more dense(hence fmic's, and the automotive infatuation with keeping your intake charge cool), so a colder intake charge is beneficial for both power and a slight increase in mpg's (as i have noticed). when i had hotter intake temps, i was losing power and mpg's drastically in my evo. a slightly longer pipe, relocating the filter and a heatshield improved my mpg's and power output, as it was getting very hot sitting so close to the turbo.

efficiency is key. and restrictive exhausts and intakes not only choke up a motor, but also decrease power output. when my 350z was all motor (complete bolt ons) i was averaging 29mpg on the freeway @60mph compared to the 25 i was averaging stock because my motor could breathe alot more efficiently. took in air and pushed it out easier than it did stock. but you do offer some good points.

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Re: Gas/MPG's - What can we do?

Postby mcrews » Tue Apr 05, 2011 12:47 am

bbs350,
When ever I go in to the dealership for work, they give me G sedans and occasionally an M for a loaner. While I will be the first to admit that they are very peppy and fun to drive, I can tell the difference when I get back in my F50.

THe corvette is a classic example of what can be done with 6 speeds and a low final drive ratio. THe vet can easily get 27-29mpg on the road turning 1800 rpm.

While I'm sure you documented the tanks of gas, this is exactly why A-B-A testing is so important. The placebo (sugar pill) effect can create the exact same result in mpg improvement . This is how drug companys test the effects of new prducts 1/3 get the new drug, 1/3 get the placebo, 1/3 get nothing. THe placebo group can show up to 1/2 as much improvement as the new drug, because people 'thing' it works. Studies show that a driver will subcounciously drive better to validate the money spent.
On the effeciency issue, again I highly suggest that any one interested in real mpg improvement go to ecomodder.
In driving for mpg, the low rpms are not effected by 'performance add ons' .

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Re: Gas/MPG's - What can we do?

Postby The00Dustin » Tue Apr 05, 2011 3:13 am

I can tell you that I definitely get worse MPGs when it gets COLDER outsde. I can also tell you I definitely and consistently get worse MPGs when it gets HOTTER outside. IOW, I believe there is an optimal temperature for MPGs that lies somewhere between 40°F and 80°F (but probably not near either of those "extremes"). This makes me think that a CAI could help at certain temperatures, but that doesn't mean it couldn't hurt at others, and bbs350z's experience could be legitimate depending on his location and the consistency (or lack thereof) in the weather there (assuming no placebo effect). I can also tell you that I I definitely get better mileage with summer gas than with winter gas. IOW, while stations have winter gas, my mileage climbs and drops relevant to the aforementioned temperatures, and while stations have summer gas, my mileage also climbs and drops relevant to the aforementioned temperatures, but my mileage is markedly higher with the same temperatures on summer gas than it is on winter gas. This makes me think that spring and fall are the worst possible times to try out mods to increase fuel efficiency, because A-B-A even testing won't do any good when the temperature is 48-72-60, and bbs350z's experience might be legitimate (as opposed to the placebo effect) but still have little to nothing to do with the mod. Have I been to ecomodder.com? No. Have I made changes to my car to try to increase MPGs? No. Is it likely that I am experiencing placebo effect because I want to believe in summer/winter gas and managed to subconciously make the same changes to my driving in multiple vehicles over the last 12 falls and 12 springs? Certainly not.

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Re: Gas/MPG's - What can we do?

Postby cruzad3r » Tue Apr 05, 2011 8:03 am

i agree :)

seriously - in the winter i noticed such low MPG regardless what car i drove. My other car is the Audi TT and it's tuned pretty well. i get EXTREMELY good MPG on that sucka but when it's cold, those MPG drops like there is no tomorrow. Same exact car, same exact distance traveling (to work and back) same exact way of driving, same exact gas - LESS MPG.

now back to the M35x - i truly think it needs another gear or two. like the newer version with 7speed. i'm sure it gets good milage.

finally - those who said "luxury does not equal economic" i said "CRAP" - look at the new M hybrid. 30+ MPG and over 300 HP, "drooling right now" :D

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Re: Gas/MPG's - What can we do?

Postby Ilya » Tue Apr 05, 2011 8:35 am

I just don't understand why Infiniti designed this car in such a way that it's doing 3k rpm at 75mph. I don't understand gearing so I'm sure there is a reason, but they could have done better. My Maxima was like 2400 at 75.

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Re: Gas/MPG's - What can we do?

Postby EniGmA1987 » Tue Apr 05, 2011 1:11 pm

better 0-60 times looks good on advertisements for a sports sedan. Thats probably the main reason for the way it is geared.

The M45 has a lot more torque, especially in the low end, so it has a much lower gear ratio compared to the M35. It doesn't need high gearing to make it get up faster and the lower gearing allows it to get better gas mileage. The m45 probably had a bump up in the ratio from the Q45 to set it apart more in the 0-60 times and make it look like there is more of an increase in performance even though it was the same engine. If you replace the rear differential on an m45 with an M35x's 3.69 gearing, you can spin tires all day long in gears 2 and 3


Gearing is all about tradeoffs between fast times and MPG. Sports sedans tend to favor faster times. You can change your gearing if you want lower RPMs, its not impossible to do. I changed my gearing to a 3.69 from a G37. This gives me faster 0-60 times than other M35 sport owners however the higher ratio also means I run at higher RPMs and thus have less gas mileage (Although in actual real world experience I still seem to have much better MPG than most...). Although an M35x gear change out is much more difficult as you have two differentials that would need to be changed and the rest of us just have one.

M35x (5 speed) gear ratios:
1st-3.54
2nd-2.26
3rd-1.47
4th-1
5th-0.83
reverse-2.76
final-3.692


Here is a picture showing different gear ratios on Infiniti's. The M35/45 are the ones on the end. I circled the M45 and AWD, the middle is the M35 base and sport:

Image




Changing to a lower gear ratio would probably have one of the largest affects on MPG as you would run lower RPMs. That, and apparently from what everyone says, a plenum spacer.

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Re: Gas/MPG's - What can we do?

Postby Double E » Tue Apr 05, 2011 2:56 pm

Just to add the the gear number being discussed, the number is a result of the drive shaft turning (from the engine) to the rear end gear that changes the longitudinal rotation of the drive shaft to the rear axle rotation that in turn, turns the wheel.

So a rear drive car changes the rotation from the driveshaft to the axle ...using a gear betwen the two to do the grunt work.

The number is a count of times that the drive shaft turns in relation to the tire. Again, the particular gear in the rear differential makes the difference in how fast the wheel turns in relation to the drive shaft. If you think about it for a minute, that means that if the drive shaft turns 4 times for every rotation of the tire, the drive shaft has to turn faster at 60mph....than say a drive shaft that turns 2.5 times for every turn of the wheel at 60mph.

This equates to a "rear end gear ratio" that means the higher the number, the higher the RPM at a given speed (higher RPM meaning more fuel burn at 60 for 4 driveshaft rotations).

The trade off is how fast that allows the car to reach 60mph. A lower number will often let a V8 engine sit at around 2000 rpm or less at 60mph but it got to 60mph slower than a drive shaft that's turning at 3500rpm at 60mph.

Drag cars sometimes run a 4.10 rear end gear. My old base model Cougar came from the factory with a 2.75 gear and it was a dog, but a fuel miser at 60mph, turning only about 1700 rpm at 60mph. I put in a 3.25 for a decent balance between acceleration with fuel economy suffering a bit.

Hope that illustration helps.

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Re: Gas/MPG's - What can we do?

Postby a.blanco0905 » Tue Apr 05, 2011 3:46 pm

I will buy the M37 hybrid when I can afford it, MPG case solved, moderator please lock thread, lol. j/k.

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Re: Gas/MPG's - What can we do?

Postby Ilya » Tue Apr 05, 2011 5:33 pm

lol blanco.

Wish I could get the M37h. Best of both worlds for sure.


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