200 miles per tank normal?

[M45Runner]

Oddly enough I don't get much better mileage when I take a hiway trip. Driving at 65 - 70 MPH with cruise control set I still only get about 23 MPG.

Me too - with the EPA rating of 16/21, I would think that if I can get 18-19 on local/city consistantly, I should be able to get 23-25 on the highway, especially when I am only driving 65-70MPH, but no, I never get pass 23 (Mostly between 21 & 22), which is odd. I thought the stop 'n go kills MPG, but how come there is not much improvement on the highway?

[YMm45]

I have m35X, which should only get about 1MPG better than a M45. I use 87 octane and have a mix of country roads and city streets on my daily drive. I am getting 21.4MPG and nearly 400 miles per tank.

I have a m45 and i do alot of mixed driving and i get about 340 350 to the tank but just wondering how your car runs on 87 i always thought it would be pretty bad to put 87 in with the compression ratio of the car

[szh]

It's impossible to compare "miles per tank" unless everyone is driving until they run out of gas.

True. I was estimating based on usage. I have only run out of gas once and that was at about 315 miles ... my first encounter with the gas gauge problem (being looked at today ... at the dealer). I had done a long trip on the highway in that period, so got fooled by the mileage and the gauge was still reading over 1/4 tank!

Some fill up when just below 1/4 (me) some wait to 1/8 and some wait until the light comes on. Plus I guarantee our guages are not exact. So . . . .

I try to avoid going much below 1/4 to 1/8 tank usually ... the low gas warning does not comes on too often for me.

Z

[About Tree Fiddy]

I'm getting about 23 mpg per the computer on my 2 month old M35 sport with about 80/20 highway/suburbia. I haven't taken it down very low but I shouldn't have much of a problem getting 400+ miles from a tank.

[shokhead]

http://tankonempty.com/

[Double E]

There is a way to get the non-A/C mode. Hit the auto button first, then the a/c mode button twice past the ECON mode and it will kill the compressor from running at all.

[NightWatch]

Me too - with the EPA rating of 16/21, I would think that if I can get 18-19 on local/city consistantly, I should be able to get 23-25 on the highway, especially when I am only driving 65-70MPH, but no, I never get pass 23 (Mostly between 21 & 22), which is odd. I thought the stop 'n go kills MPG, but how come there is not much improvement on the highway?

The M35 is a pretty heavy car for a 6 cylinder. I think maintaining 70-75 MPH on the highway with this mediocre transmission puts a load on the engine so the MPG is lower. I had a G35 coupe with pretty much the same engine and I would get 28 - 30 on the highway at 70 MPH.

[myellen]

I have a m45 and i do alot of mixed driving and i get about 340 350 to the tank but just wondering how your car runs on 87 i always thought it would be pretty bad to put 87 in with the compression ratio of the car

Regular unleaded is all that is required for the 06 M35X, and premium is recomended for increased performance. When I first bought the car, I filled up with regular and drove it like an old man, to see what fuel economy I could get. Then I filled it with premium 91 and did the same. I could not see any increase in MPG, so I have been driving with regular ever since.

This is directly from the owners manual.

VQ35DE engineUse unleaded regular gasoline with an octanerating of at least 87 AKI (Anti-KnockIndex) number (Research octane number91).For improved vehicle performance, INFINITIrecommends the use of unleadedpremium gasoline with an octane rating ofat least 91 AKI number (Research octanenumber 96).

[YMm45]

ohh okay that is true i did not even notice you had a m35 i was thinking m45 but it is bad to run that gas in a m45 correct

[myellen]

ohh okay that is true i did not even notice you had a m35 i was thinking m45 but it is bad to run that gas in a m45 correct

I am not an expert even in my own imaginary world, but I believe that running 87 in a m45 will not hurt it, but you may get some engine knock.

Prolonged engine knock due to insufficient octane, probably is bad, but may not happen.

I know that I have run a full tank of 87 octane in a new G35, which "requires" premium, and it was still balls to the wall fast and had no sign of degraded performance or engine knock.

[fiveliterbeater]

all of our motors are equipped with knock sensors; we can run 87 octane as long as we want, when we want. all the computer does when engine knock is detected, is pull timing and readjust the fuel curve to a more "rich" condition to avoid engine damage. also a reason why our cars run sluggish in the summer but that's a whole other topic for another day. can you really imagine how many lawsuits would be filed against car manufacturers if these cars solely ran on 91+ only and would break if you tried to put in anything lower than 91?

...and by the way, why does everyone call gas that has an 89 or 87 octane rating "bad" gas? the only differnce is the amount of octane mixed inside.and besides, people have this mis-conception that octane makes your car go faster when in reality it's a "flame retardent" which means the more octane, the longer it takes for gas to ignite. you cannot put straight gasoline with no octane in your tank or the fuel would never reach the combustion chamber. it would explode waaaayyyyyy before the piston reaches TDC (top dead center)

[NightWatch]

I noticed a considerable difference in both performance and mileage when I had to run a tank of regular 87 octane gas through my car when I couldn't find any 93 or 91 octane back when we had a gas shortage in GA. The car was sluggish, it stalled and I my average mileage of 21 MPG dropped to 17 MPG. I wouldn't run anything less than 91 through it again.

[tigerclaws1318]

After driving 176.7 miles from a tank full I decided to go fill the tank up again. It took 14.173 gallons before clicking. After doing the math my mpg was 12.4 which is exactly what it said on my trip computer. I do baby the car 85% of the time and will be trying to achieve better numbers as far as mpg wise. Let me know how you guys do as far as mpg.

Oh yeahh, summers right around the corner meaning gas prices will be going up.

[paigoomein]

I have the 2007 M35 (non-sport, RWD) and average anywhere from 21 to 23 MPG using 91 octane. I have tried 87 before but noticed that I would get a decrease of around 1.5 in MPG.

Let's say I average 22 MPG--a decrease of 1.5 MPG is around a 6.8% decrease. Back when gas prices were high (around $4.50 per gallon for 91 octane), the $0.20 price difference between 87 and 91 octane translated to only ~4.4% difference, meaning that it made more sense in terms of both price and care for the vehicle to use 91 octane. with gas prices lower, it's not as easy to make that comparison (with 91 octane at around $2.50/gallon, meaning $0.20 is ~8%), but I still use the 91 octane.

[M45Caliber]

XXNite stated In my '04 M45 (50k miles), I ALWAYS put the factory AC control on "ECONO" setting, instead of letting the compressor run like crazy. It's a shame you can't completely disable the A/C compressor from coming on, too. This is the only car I've ever owned that won't allow you to just blow "air" without the compressor running? gotta always crack a window or the sunroof with the system off.

M45Caliber says --- Ahhhh Grasshopper -- you no read owners manual! I too was unenlightened about the AC compressor -- UNTIL I read the owners manual to find out what I was missing.

So, turn on your AC -- top right of screen says A/C now press the "6" button on your radio station keys (I think it's the 6!) and the small orange econ box lights up, and the A/C in the top right goes off. Push the "6" button again and the orange econ light goes out AND the A/C is still off -- THIS, Grasshopper is known as compressorless nirvana. This is how you can get air circulation with NO parasitic losses.

And, BTW -- run some BG44K through that beast and change the air filter! It was PAINFUL but I actually made it through 200 miles of "old geezer" driving - light acceleration and coasting to stops, etc. and managed almost 20MPG is mostly local suburban (i.e. little freeway) driving.

So something isn't right if you are only getting 14, because I drive the stink outta mine most of the time and get 17 (and BTW, I am an old geezer to most on this board @ 58) .

[M45Caliber]

if the only difference being discussed is that of octane, only performance at the high end of the spectrum, or under load, should be affected. The car (all new cars) compensate for octane (or lack thereof) and adjust the timing accordingly. So, under full throttle or travelling up an incline, you would notice a slight decrease in total torque and horsepower, thus, performance.

In day to day driving it should be imperceptable. Your fuel mileage is controlled by a computerized air/fuel ratio and octane really doesn't impact that, so no mileage differential should be detectable. However, most Tier 1 premium fuels have more additives and that might be beneficial in the long run for your intake, injectors, valves, piston crowns, etc.

If you are going to measure any difference in fuel mileage, you will need to perform a closed loop test with the exact climatic and driving conditons, using the same driver and technique. Furthermore, the driver can NOT know what fuel is being tested each time, so as not to impact the technique utilized. Way too many variables for us ere mortals to control, but you could use regular for a month, then premium for a month and see -- assuming you drive the same exact routes and speeds both months, which is still all but impossible to do.

You won't hurt the car using 87 octane, but Infiniti recommends (M45 is what this post was about originally) premium for a reason. At $0.25/gal more, and figuring 12,000 miles a year at 18 mpg, you will spend about $167 MORE annually (or $14/month) for premium over regular.

You just bought a $45,000 + car -- so you decide if it's worth it. Do you extend your oil changes out to 7,000 miles to save money? Why not? Think it through and do what you feel is best for your situation. If you are leasing and don't plan to keep the vehicle past the 36 month (or whatever) term, then regular will suffice and the next owner can deal with any issues that might arise.

From the Web - Octane Myths• High octane gasoline improves mileage.In general, if your car is designed to run on 87 octane gasoline, high octane gasoline will not improve mileage. If switching to high octane gasoline does improve mileage, you might find that your engine, or its control systems, need repair.• High octane gasoline gives quicker starting.No, it doesn’t.• High octane gasoline increases power.If your car is designed to run on 87 octane gasoline, you shouldn’t notice any more power on high octane gasoline. Again, if it does make a noticeable difference, your engine, or the engine’s electronic controlsystems, may need repair. (NOTE: Infiniti recommends Premium for M45)• High octane gasoline has been refined more – it is just a better product.Additional refining steps are used to increase the octane; however, these additional steps do not necessarily make the gasoline a “better” product for all engines. The additional additives might, however.

[ken in az]

I thought that the 2ng gen M45 engine(could be the same for 1st gen) had to run on 91 and even in the owners manual it says that if lower octane fuel is used engine damage can occur.

This is primarily based on the fact that the engine has 10.5:1 compression ratio.

Fiveliterbeater, yest the ecu can pull timing, but it can't lower the compression ratio which is what necessitates the need for higher octane.

I beleive the owners manual states that if you do have to use the lower octane fuel, then not to exceed 3500rpm and avoid hard acceleration.

[jbillion]

If your car is designed to run on 87 octane gasoline, you shouldn’t notice any more power on high octane gasoline.

The M45 was not designed to run on 87 octane, it was designed to run on 91+.

[M45Runner]

The M45 was not designed to run on 87 octane, it was designed to run on 91+.

That is true. If you want to get the rated 335hp out of your engine, you need to use 91+. But, to run on 87 octane will most probably not hurt the engine as long as your knock sensor is fully functional and you are not doing WOT. There is a reason why Infiniti says not to exceed 3500RPM when using 87 - the timing might not be able to adjust quickly enough after the knocking sensor detect a detonation. So, as long as you stay under 3500RPM (even 4000RPM), it is fairly safe to use 87 - granted you will lose some hp and the gas mileage will be slightly lower (around 5-10%).

[szh]

The M45 is designed for 91 octane, yes. While the engine management system will compensate to some degree on the occasion that you have less in the car, it is also possible that you may also have some bad gas or water or whatever in the engine. Then, the compensation fails to work totally and you get audible pinging and knocking.

Furthermore, the compensation does not kick in instantly. The sensors have to detect the occurrence of knock and pinging, etc. And, this "silent" pinging can, and will, lead to problems over time - you are hurting the engine, whether you want to recognize it or not, since it is expecting 91.

Finally, my main point is always this: with most people's driven miles/month, the cost difference between using 87 and 91 octane is typically between $10 to $15 - perhaps $20 worst case. Is this really a big amount of money to anybody who has purchased a luxury car like the M? If so, then it would be better to (a) not purchase the M, or (b) sell it and get something that gives you the financial return you need.

This last is not meant to be insulting or pejorative in the slightest! It is a practical fact of reality today that people have financial problems sometimes (particularly in this economy) and it is better to acknowledge it, and do something about it, rather than motor on and do short-term things that don't help in the long-run.

Z

[xxNite]

Thanks Double E & M45 Caliber... I am guilty of not catching that in the owners manual.

I am a old geezer (sort of... pushing 40) so I like just cruising easy. I made the silly mistake of ordering and installing the TEIN S-Tech springs and am always scraping the front lip or union connection for the exhaust under the car. (Philadelphia PA roads are so trashy)

Well, I now look forward to better gas mileage without the A/C compressor running until it gets stupid-hot this Summer.

Thanks again

[TREYDEE007]

I get better gas milage out of 87 than I do with 93

I get around 320-360 with 87 and a lil less with 93, that 60%hwy and the rest city.I use cruise control alot even in the city,and I let the car coast alot to redlights also.

[M45Runner]

I get better gas milage out of 87 than I do with 93

Are you sure it is not caused by the Need for Speed The 93 octane gas will give you extra performance (hp) and for me, it is very hard to resist, which result in more WOT and less MPG.