**please correct me if anythin is wrong**

[background]
according to cars.com, 4th gen maxima runs 22 mpg in city, 27 mpg in city approximately.

[old-run info]
i do a good 50/50 city/hwy run every tank in a 16 gallon in an automagic transmission. runnin 87 unleaded. oil change always on time, stock tires 205/65/15 runnin @ 29 psi all around. i keep my car lightweight with few exception of school textbooks. mods are in my sig.

i get between 275-300mi per tank.

[new-run info]
i still do a 50/50 city/hwy run. now i do my own oil change at home, runnin 91 premium at various gas stations. oil change always on time, front tire is 205/60/15 runnin @ 33 psi, rear tire is 205/65/15 runnin @ 34psi.

i get AT LEAST 300mi per tank, and i have gotten 330mi 2 times.

[conclusion]
1. although stock spec "suggested" 29 psi on all tires, but runnin higher psi will lessen the load on the tires, which gives better milage
2. shift_3,000rpm
3. oil change on time, the car gains better performance as well as milage

 

Yeah, its a pretty well known fact that raising tire pressure will increase gas milage, btw I dont think our cars are supposed to run on 87 octane.

 

i always have follow stock spec, i never thought raising the tire psi will significant gas milage. and yea i was cheap, i didn't really bother about maxima maintence until i started takin the car seriously.

 

Yeah the tire mileage set by most manufacturers favor a soft ride over handling or fuel mileage. I set my 17's to 38F, 36R. Sounds high, but I get responsive steering and good wear at those settings.

And about regular or super. You can use either, won't hurt the engine one bit. You will get a little more power with super, but if you can't tell the difference using the cheap stuff, then you aren't doing the wrong thing by using it. Super does not have more detergents than regular.

 

yeap...i'm still learnin and experincing... i jus thought to share with u guys wat i discover tat's all

 

happy: good theory, makes sense.

I'm in the process of writing a MPG Q&A that can be added to the FAQ, that way, we can pool all our ideas about getting the best gas mileage into one collective post.

the only thing i've noticed between using 87 and 93 is that even tho 87 is cheaper, 93 gives me more MPG, and is more cost-effective in the long run.

Example: Last tank, i filled it up with 87 octane. I got about 275mi to the tank with about 75% higway/25% city driving.

This tank, i filled up with 93 octane. I'm at a little under 1/2 tank right now, and so far, i've gotten 249mi out of it, with 50% highway/50% city driving.

 

yea, i'll be interested. we jus have to find a way to collaberate all the data from tire size, tire psi, type of gas, mods, maintaince, and other misc. components tat affects gas milage.

i believe people on the forum are interested to find out how to get better milage, especailly when gas is so expensive and max use up so much gas.

 

may be true

however,
factor in that running tire pressure at higher PSI than suggested by the manufacturer may very well result in faster, uneven tire wear.

 

I have also noticed that there is a significant decrease in gas mileage when doing short trips. This seems obvious in the sense that the engine will be in the lower gears more often , but I've also noticed that doing short trips continuosly gives better mileage than doing those same short trips with breaks inbetween. Seems like the VQ runs very rich when cold.

About 70% of my driving is trips less than 3 miles with breaks between allowing the engine to cool. I usually get between 19-20 mpg. I know its those short trips that kills the mileage since I have no problem getting over 27 mpg on long highway trips with cruise set to 72-74.


ps- on the other extreame - I found out yesterday that averaging 90.44 MPH on a 208 mile trip still gave me 18.9 mpg.

 

i typically get about 22-24MPG in my 4th gen, but man, when i get on it on the highway (i travel around 85-100 consistantly, many times faster) it burns alot of gas...




Eric

 

I usually make it to a little over 300 miles on a full tank of gas. I don't race my car, I don't push it for no reason, and I try to keep it under 3.5k rpms (most of the time ).

EDIT: Nothing but 92+ octane goes into my baby.

 

I got 286 miles on 16.37 gallons of fuel 92 octane. All city driving... very limited High RPM travel.

Just put in new NGK Plat plugs, K&N Air Filter, changed the oil to Mobil 1, ran a couple of tanks of injector cleaner, and cleaned the throttle body. The car runs great, the gas mileage still sucks..

What next ????

 

Those of you who do not understand octane, you probably should get a lesson. If the manufacturer says to use the 91 or higher, maybe it is wise to heed the advice. Running your MAX on a lower octane fuel WILL cause problems in the long run. By the time you start to notice, it may be too late. Come on, get real! The manufacturer makes money on the car, not the gas you buy. Low octane in a high-performance engine can lead to pinging, and if not properly corrected (in time) you may have an expensive (knock-sensor could go nuts) repair, or even worse--an engine overhaul. Use the higher octane. For the few cents cheaper it is, you save hundreds in the long-run by avoiding repairs. Be good to your cars, and don't assume that if you don't notice a difference from the cheap stuff, then there is no difference...because there IS a difference. Check out some of the FAQ's on octane ratings for high-performance engines.

 

Knock sensors are around 130, they're pricey but they're not that expensive.

 

While this is true, and running your tires at over pressure will increase your gas mileage, your traction will decrease significantly, especially in the rain.

A little math for you.

Maxima = 3000lbs (to make things simple)

tires at 30 PSI = 25 square inch contact patch.

tires at 38 PSI = 19.7 square inch contact patch.

(Weight of vehicle/Pressure in tires)/4 = Contact patch size

The less tire that touches the road, the less traction you have and the less safe it is in poor conditions. Stopping distance is effectively increased and it is more likely that your wheels will lock up in hard braking or you will skid out around hard cornering.

Please inflate your tires to the recommended tire pressure, especially if you are behind me and have to brake hard.

 

300mi per tank seems AWFULLY low on stock rims. I get just above 300mi per tank now on my Konig Tantrum 18x8s with CAI + Y + MEVI and pretty spirited driving. These are heavy rims, almost 24lbs each I believe. Anyways, when I was running stock 15s, I consistently got 370miles per gallon, if I did a LOT of highway cruising, I can almost get to 400. When I was stock, I usually pumped up the tires to 31 or 32psi...

 

If you're referring to my post, I'm not on stock rims (not sure on the weight of them), and most of my driving is in the city. 370 miles+ is amazing...

 

Go for the front (left) O2 sensor. This "front-left" sensor measures the air mixture and regulates how much gasoline is injected for burning. If this sensor goes bad, it will provide faulty readings to the ECU, telling the computer that the mixture is lean and neats to be enriched. The computer will then cause more gasoline to be injected for burning to compensate for the lean reading. This will cause your gas to run rich, dumping too much fuel into the system (the system thinks it is correcting the problem by adding more fuel) and killing your mileage. The other two O2 sensors measure readings AFTER the fuel/air mixture has taken place so, in effect, if they fail it will not affect your mileage.

 

Man i cant imagine getting some of the mpg figures some of you do. I drive a bone stock 99 gxe 5 speed. I've driven 428 miles on one tank. I get 27 mpg while doing a constant 80mph. I'd probably get 1-2 mpg more if i drove at 65. What are you guys doing to get such horrible mileage. Mind you yes that is all highway driving. But even city driving i fill up when i'll be at 365 or so, with some to spare. Are your mods to blame? I'm just curious, because whatever you guys are doing, i want to make sure i avoid doing that at all costs.

 

My Car is completely stock... with the only exception being the K&N filter.. which should be no big deal... tire preasure is right where it should be. I am leaning toward the front left left O2 sensor as recommended in an ealier post. Thanks

 

where did u get the contact patch numbers from???


n e who, i drove my car for 113.6 miles all city and the fuel needle barely moved beyond 1/8th so for shlts and giggles i filled'er up and i filled in 3.405 gallons and that comes out to 33.36 mpg... of course during this time i drove the car worse than a gramma... shifting at 2 k and often times from 3rd to 5th....

 

Read the post again (I hate having to repeat stuff), I put an equation in there. Its actually pretty simple. Take the weight of the vehicle, divide by the tire pressure in the car, this will give you total contact patch area. Then divide by 4 (4 wheels duh!) to get the contact patch of each tire.

Obviously this isn't taking into account centripetal forces and doesn't say anything about the shape of the contact patch. But it gives you a general idea, and that's all you really need unless you are actually modelling the contact patch surface. If that were tha case, I wouldn't have to explain it again.

 

'95 se 5SPD with all suspension aftermarket. stillen exhaust. stillen hi flow. '91 300zx 16" wheels. Long trips get me 430 miles between fills. 50/50 city and highway driving gets me around 320 miles between fills.

Gotta love the max...

 

I can't see how this equation is anywhere near accurate or even remotely valid. So you are saying that the area of the contach patch is a function of only weight & tire pressure? Whatever happens to tire width, tire circumference tire profile design etc.
All you are doing is taking the weight of the car in lbs, and dividing it by psi (lbs per square inch of tire pressure).
If what you are saying is true - then the heaviest car with the least tire pressure should have the most contact patch and therefore best grip?

 

sorry i should re-phrase where did u get that formula from?

 

yeah i have to agree i REALLY dont follow that formula at all... from what kushane said "If what you are saying is true - then the heaviest car with the least tire pressure should have the most contact patch and therefore best grip?" that sure as heck dont make any sense to me!

 

I get upwards of 375 miles/tank. Tire pressure at 33 all around. recent fuel filter change, new spark plugs, and ALWAYS 93 octane. And I'm a 5 speed. Last week I went 170 miles on one trip. All highway driving w/ cruise set at 80mph. I filled up when I got back and 170 miles only took 5.3 gallons. 170/5.3 = 32 mpg. Last oil change was 2,000 miles ago with 10W-30.

 

I get 350 or more on 17 gals..

And I drive fast, at least twice a day I tach 1st gear all the way out (automatic, so 45mph)

I always fill up with 17 gallons, so make sure you divide it by how many gallons you used and not just 18..

I don't seem to do anything special and get 20-23 mpg and I do mostly city/backroads driving..

 

I might have just learned something new in this thread

 

btw it seems very unconstant miles per tank between each member on the org, some people are gettin above 300+ mi, or even 350... and some people are only gettin 275mi the best i hope we can sum up a general conclusion to get a better milage.

 

OK, so increasing your tire pressure by 8 psi reduces your contact patch by 5.3 square inches. That means a 21% drop in surface area. Doeas that also means a 21% drop in braking force, cornering force etc?


By the way, happyricefob, you should make your front tire pressure higher than your rear because of the heavy front weight bias of the car. With the rear tire pressure higher, you make your car much more likely to oversteer.

DW

 

So definitely the maxima gas tank has a capacity of 18 gallons?

 

i believe its 18.5 to be exact. n e wayz, if u guys REALLY want better gas mileage in the city let the sucker shift at or a lil after 2 k through 1,2,and at 1.5k 3rd --> 4th, and 1.5 k 4th --> 5th thats how i got my 33.36 for 5 speed guys at least. also, when ur accelerating gear to gear, dont get the car to 2k fast just slowly depress the pedal, i know no ones gonna do this, but this is how i got 33.36, its not really that bad driving like that.... really .. its not

 

wow...we dont drive mustangs...theres a whole 4.5KRPM after 1.5K, don't you miss those?

 

*sigh*

www.howstuffworks.com/question506.htm

I know this post is long, but if nothing else, just read the above link before replying.

Its really simple. That calculation has been used for quite a long time to obtain approximate contact patch sizes.

You are right, a heavier car with less tire pressure will result in more contact patch area and more grip. However, as with many many many things when it comes to performance, you have to sacrifice one aspect to get performance in another. In this case, you increase your rolling friction greatly and a lot of energy is lost there because the tire has to deform more as it rolls, hence why if you increase your tire pressure, you get less rolling resistance, and better gas mileage. Its the exact same principle. Ever wonder why you're supposed to decrese your tire pressure when driving in sand, mud, ice, or snow? Its to get more surface area of the tire to work with in contact of the ground to avoid slipping.

If you decrese the pressure too far, you will risk riding on the sidewall, which will actually decrease your contact patch area because the sidewall will end up carrying the majority of the weight. Also, you risk unseating the bead from the rim. Not a good situation.

Of course there are other aspect that come into play when calculating exact contact patches, namely thickness of the tread and pattern of the tread, but for the numbers you'll ever need, the equation I listed will suffice.

In no way does this tell you anything about handling and lateral traction, only surface area contacting the road. If you have really skinny tires at a particular pressure, you will have a more square contact patch (obviously with rounded corners). If you have wide tires on the same car at the same pressure, you will have a more of an elongated rectangular shaped patch with the long sides going laterally. However, the contact patch are will be the same size, although not the same dimentions. You can obviously see from this example that wider tires are better for lateral traction as there is a larger cross section in that direction. However, with wider tires, you can sacrifice some traction in the front to back.

If you have trouble with tires slipping off the line, try decresing your tire pressure by about 5 to 10 PSI, and see what happens. You will note it is a little more difficult to spin the tires (although with the Maxima, I wouldn't doubt you'd spin them anyway). However, just because some is good, doesn't mean more is better. Once you get that initial traction and you get rolling, the ideal tire pressure is higher because you want less rolling resistance for higher track times.

Even my boss (holds a BS in Mechanical Engineering and an MS in Aerospace, both from Virginia Tech) used that equation when we were doing skid sensor testing for a proprietary tire manufaturer. We wanted to simulate a tire's contact patch rolling on the ground, so we decreased the tire pressure so we didn't have to apply as much force to get a decent sized contact patch for our testing.

If nothing else, think of it this way, try going to the air pump, and note how your tires sit on the ground. Notice there is a pretty nice flat area on the tire where it meets the ground. Well, now try filling up your tire to its maximum tire pressure rating (should be somewhere around 60 PSI), you will notice the tire in that spot become more rounded. The contact patch has become smaller.

Yes, the equation really is that simple.

 

Thank!
Great explanation.

 

i get 330-350 for 15.5 gallons everytime. my tire pressure is at 40psi on the stock 15's and dunlop a2's. car feels better too when running higher psi. turns arnt as mushy.

 

i just filled up my tank today at 271 miles, and i had been going WOT alot this time around bc i had installed a pop charger and now have my midpipe in... 11.16, got 24.3 mpg i dont know how u guys are getting such bad gm, are u guys mostly autos? or 5 spds?

 

I have an Auto... I really think it's the O2 sensor. Will know this weekend.

 

I just Installed the new O2 sensor... no troubles... do I need to reset the ECU?