Fuel Economy

[elwesso]

I am wondering what kind of fuel economy most of you get on your Qs. I just figured mine out today, and i get 11mpg, which is mostly city driving. I think that it should be higher, especially since the EPA rates it at 14 in the city. Its mostly just driving slow, with not too many stops. I usually let it warm up for about 3-5 minutes before i head out, and drive easy until it gets up to operating temp. I think that my economy should be much better, considering I floor my GTP all the time and still get better mileage. What are some things that I could do to increase fuel economy, without having to do too much mechanical work. Are there any additives that work good to clean things out? I could do some moderate underhood work, maybe replacing o2 sensors if they are easy to get to, but nothing too involved. Thanks for the help.

BTW, i have a 94Q. I have searched the board already numerous times, and didnt really find anything that was completely relavent. I know to search, since I am a moderator on another board ( http://www.cadillacforums.com ) and I get redundant questions all the time.

[landtodd]

Around town cold, 10 mpg is okay. 16/22 EPA is about right

[Q45tech]

Indiana? Are you in an area with oxygenated fuels? This will drop the city mileage by close to 10% [for sure 5% minimum].

You said 14 mpg EPA is yours a Q45a [active car]?

[Mayhem_J30]

Indiana? Are you in an area with oxygenated fuels? This will drop the city mileage by close to 10% [for sure 5% minimum].

You said 14 mpg EPA is yours a Q45a [active car]?

Southern Indiana doesn't they have the good stuff. That's why a lot of Louisville, KY guys drive across the bridge to IN to fill up.

[elwesso]

Well, mine is the base Q (no A).

Anyway, im not sure if they use oxygenated fuels or not, but if you know, i am in central indiana. So is there really anything that i can do to improve my mileage, because spending $40 to fill up is killing me. Even if i did something to only get a few MPG that would help.

So if i am using oxygenated fuels, when do they start switching back to non-oxygenated fuels? And when they do switch back, i should see an increase in MPG? So you all think that this is not unreasonable.

Kind of off-topic, but i got an estimate on fixing my seats, and to replace the bottom seat cushion for driver and passenger, and the side lumbar cushion for the driver is going to be 463.50. Does this seem reasonable? They are using real leather.

[Woodmister]

My seats have cracks and tears in them and after ducktaping them I found that these seat covers at Costco for like $19 fit the huge Q seats. Plus in cold weather like VA, it helps prevent against the freezing of your @$$ syndrom

Also I get about 300miles in 1 tank of gas for 30 bux...$1.71 per gallon (Premium @ Costco membership)

[maxnix]

spending $40 to fill up is killing me

To spend less, and extend your fuel pump life, always fill when your tank indicatior reaches the ¼ full mark. Running it until empty or near empty stresses the fuel pump, causing it to fail sooner. It's in the threads.

[elwesso]

What i do to fill is i wait until half tank, and I alternate between premium and mid grade. Its not as harsh on the wallet, but gas prices are just insane.

So what about that other stuff i mentioned, do any of you know if oxygenated gas is sold in cent. indiana? Also, is there anything I can do to help this, or am i just going to have to bite the bullet?

[j30t]

I have an idea...drive your pontiac if it get much batter gas milage...or else youd just have to pay the high prices

[Woodmister]

That Honda Insight lookin nice right about now isnt it?

[6speedG35sedan]

I just put a K&N airfilter in my 03' G35 sedan and did the first oil change and went to Valvoline Syn Pro and this last tank of gas I got a true 1.5 miles more per gallon. I'm getting 20 mpg combined city and Hwy. What do you guys think of synthetics and K&N?

[maxnix]

Synthetic lubrication good. K&N, dirtier than stock, no performance gain.

Read the posts and you'll see why.

[elwesso]

That Honda Insight lookin nice right about now isnt it?

mmmmmmm, 50MPG!!!!!!!!!

I just put a K&N airfilter in my 03' G35 sedan and did the first oil change and went to Valvoline Syn Pro and this last tank of gas I got a true 1.5 miles more per gallon. I'm getting 20 mpg combined city and Hwy. What do you guys think of synthetics and K&N?

Synthetics- If the car doesnt call for it, what is the benefit. I put in what the MFG says. The only advantage that synthetic has is it lasts longer, but if you bought an expensive car like that you are going to change the oil regularly anyway. Also, synthetics have more of a drain back, whereas regular oil tends to stick to the components. So when you start your car, there is less oil on the internal components when it first starts than with regular oil. So in the first few minutes there is much less oil on these components until the oil circulates through.

K/N- Not worth the money, IMO. They provide less filtration, which leads to more engine wear. They say they provide more filtration, but that is after it is dirty. The oil stuff you put on it catches dirt, not the actual fibers. The OEM will give you enough filtration and wont give much more restriction than the K/N. Personally, i would sacrifice .5 HP (which is about all K/N gives you) than have more dirt in my engine. The MAF and other sensors in the intake are calibrated for the OEM filter, and sometimes the oil from the filter can get mess up the MAF. The K/N people will tell you that it doesnt matter until they are blue in the face, but more times than not MAFs are messed up because of K/N.

[greg_atlanta]

Ditto on K&N, will let more dirt in the engine and cause problems long term.

All new cars' mileage with get a better as they age. (Most G35s were bad for the first few fillups).

Synthetic oil is a good idea but the impact on mileage is minimal.

Making judgements from week to week about mileage is pointless since driving conditions, weather, and fuel formulation change a lot. (And every pump has a different sensitivity level for fuel cut-off). Look for long-term trends.

[greg_atlanta]

What i do to fill is i wait until half tank, and I alternate between premium and mid grade.

Anything less than 91 octane will make mileage worse. I'd stop alternating gas types.

Does the car ever get strenuous exercise? Just running around town forever is BAD for a Q45. A road trip with a can or two of good injector cleaner will make a world of difference. Engines that never get hot for long periods of time get crudded up very fast. (intake and injectors)

Get a professional intake and injector cleaning done too.

[elwesso]

Maybe synthetics are better for the infinti engines, but i have heard it doing more bad than good on other engines (like cadillacs Northstar).

[elwesso]

Anything less than 91 octane will make mileage worse. I'd stop alternating gas types.

Does the car ever get strenuous exercise? Just running around town forever is BAD for a Q45. A road trip with a can or two of good injector cleaner will make a world of difference. Engines that never get hot for long periods of time get crudded up very fast. (intake and injectors)

Get a professional intake and injector cleaning done too.

I try and open it up every now and then, which is what probably kills my mileage. But it gets ran hard every so often. It usually ends up being about once a week. Even when i drive in the city, i let it get up to operating temp.

What kind of additives do you recommend???

[maxnix]

Synthetics- If the car doesnt call for it, what is the benefit. I put in what the MFG says.

When you read the posts on oil (we have some very technically qualified people here including TexasOil and Palmerwmd, among others), you will learn the advantages over standard oil stocks.

Same for "MFG" maintenance when you read the posts; recomended maintenance is usually just minmally sufficient to get the car through waranty. After that, you're the sales department's.

[msscomm]

r.e. Fuel Economy

Averaging about 15 to 16 around town with the 96 Q - and I DO have a very heavy foot -

20 to 22 on freeway trips of several hundred miles -

Will be finishing a Throttle Body / fuel induction system cleaning and would expect to pick up a bit more MPG in the around town driving, and keep that purring machine going.

And all this with that California sulpherd up, oxegenated 91 octane crap we have the priviledge of paying through the nose for (San Diego is just about the highest in the nation @ the pump) - Thank you soooo much to Govenor Grey Doofus and all the CA eco-wackos !:bash

[VimyJ]

And all this with that California sulpherd up, oxegenated 91 octane crap we have the priviledge of paying through the nose for (San Diego is just about the highest in the nation @ the pump) - Thank you soooo much to Govenor Grey Doofus and all the CA eco-wackos !:bash

While doing some research for someone, I came across information that California's gasoline supplies are under greater pressure than refining capacity can handle because of the increasing number of SUV's bringing down over all fuel efficiency and the growing amount of distances being driven on an average trip.

I don't know if you are old enough to appreciate it but when I was a kid visiting S. Cal in the late 60's and early 70's the air pollution was staggering. You could notice the smog when looking across a typical lawn to a car in the street. It's much better now than 20 years ago thanks to better fuels, cat. converters and cleaner burning engines.

[msscomm]

I don't know if you are old enough to appreciate it but when I was a kid visiting S. Cal in the late 60's and early 70's the air pollution was staggering. You could notice the smog when looking across a typical lawn to a car in the street. It's much better now than 20 years ago thanks to better fuels, cat. converters and cleaner burning engines.

I was actually born in San Diego and clearly recall having my eyes tear up when we were up in Pasadena due to the ungodly thick air pollution in the 60's. My sisters complained they had to wash their hair daily as the pollution was soooo bad up there.

BTW - in the early 90's when I lived in Newport Beach and commuted inland (against traffic - YEAH ! !) it would be wonderful on the drive inland up the 55 / 57 but by noon, you could NOT see the Base of the San Gabrial foothills from 20 to 30 miles away that you could see in the morning - and we were BREATHING that stuff every stinkin' day !

[elwesso]

Not to change the subject or anything, but what kind of additives do you guys like??

[greg_atlanta]

Averaging about 15 to 16 around town with the 96 Q - and I DO have a very heavy foot - 20 to 22 on freeway trips of several hundred miles -

That's about right for any 90-96 Q. Don't expect it to get too much better. But more maintenance is always good.... car will run better and make you want to drive faster and thus burn all the extra fuel you save!

[maxnix]

With OBDII and less timing overlap, the 1996 might run a little leaner and more efficiently. Anyone know the EPA projected mileage for a 1995 Q45 vs. a 1996 Q45?

[elwesso]

If he is getting 16mpg in town with a 96 and I have a 94 and i am getting 11mpg, something is obviously amiss. Even with oxygenated fuels (with a decrease of ~10%), I should be getting at least 15mpg. So what is the protocol???

[maxnix]

Mileage figures are not absolute as it depends on use, state of tune, fuel quality and condition, and use patterns.

Assuming a well maintained engine (clean intake path, filter, IAC, adjusted timing and TPS, properly performing injectors and fuel delivery system), you probably should do better.

I know my mileage decreases significantly because of longer initial warm-up times in the winter. Highway mileage is pretty much constant since summer heat in Seattle (maybe 85ºF) is usually not much of a factor.

[elwesso]

What should I do to determine the if all those things are what they should be? It seems to run smoothly.

Do you think spraying a little TB cleaner in there would be a good idea??

[maxnix]

Cleaning the TB and intake path is always good (has it been done?). Search the threads for pointers and member's techniques.

If the cold start and idle are correct and smooth, only a Consult could indicate otherwise undectable out of specification components. Of course, the Consult is a tool, and tests conducted must be read and analyzed by an experienced Q45 senior technician for complete confidence. It is not necessarily a solution in itself.

[msscomm]

What should I do to determine the if all those things are what they should be? It seems to run smoothly.

Do you think spraying a little TB cleaner in there would be a good idea??

As an old shadetree mekanik - I'd first strongly suggest you bite the bullet and find someone who can read a Consult for a detailed diagnostic - the biatch of it is finding a smarter than average bear you can trust - My personal recommendation would be swing through Cali on a run to TX and have Jerry tell you the TRUTH at Jerry Tucker's AIS in San Diego - Beats the daylights out of “replacin an’ prayin” - Hey, what’s an extra 500 miles in a guzzler, but I’m guessing you’d be smiling runnin down in that Q

I heartily concur w/the more mechanically inclined that basics such as Spark Plugs and an induction system / TB cleaning is just about the cheapest thing you can try until you have your little "come to Jesus meeting" with the Consult and a real Pro diagnostician.

Whttya Want for nuthing (280 BHp), RUubbbber Biscuits ?

[elwesso]

I am going to take it to Infiniti one of these days, but until that time, do you think injector cleaner and/or throttle body cleaner that you either spray directly in the TB or put in the gas would be worth the money???