i would reset it just in case

 

Reset the ECU because since the computer stores the code, it may retard other functions, thinking that (since the code is still there) the problem still exists. I replaced my O2 sensor and have not yet reset the ECU. I recently scored a 400+ mileage (18.5 gallon tank) on a road trip, whereas before (w/ bad O2 sensor) I was getting much less (16-19 mpg). I will reset the ECU today.

 

Also, if O2 or other emission codes are stored in the ECU (at least in Utah), you will not pass emissions inspection. Case in point, I went to have car inspected (reset ECU, had NOT changed O2 sensor yet, but code had not yet re-registered) and I passed w/ bad O2 sensor because there was NO code stored.

 

resettin the ECU will cause the car to relearn the way u drive all over again... =/ don't reset too much...

 

Thanks for the responses, I have just reset my ECU... I did check the codes and got a 5 and 5. So there has been no issues since the last time I reset it. My mileage has improved. I have run 160 Km's on a quarter of a tank. The best I was able to do before was about 110 - 120.

 

One day I was checking my gas mileage, and when I filled my gas tank and set my trip, it was on like 90,000 miles on my regular mileage gauge...So after 350 miles or so the regular gauge was at 90,350 but my trip was at 346miles so they don't read the same.Anyway I drive 50/50 city-highway driving and I always get about 350 miles a tank Highway only around 400 miles a trip...75 to 80mph average 32psi allaround always 93 oct...

 

haha believe it or not u can get still get some power out of the car this way just gotta be smart about it. ever since i got my mid pipe i haven't been using this strategy so um yeah lol

 

The keyword here being some

DW

 

hahaha well i still get 24 mpg city not driving that way so im happy.... now for my differential bearing .... hopefully thats not what my problem is right now

 

I now have run a couple of tanks after all the changes I have made.. here is the data:

Enter Kms 470 ....... Miles 292.058
Enter Litres 58.3 ....... US Gallons 15.40286
per Litre 8.061749571.... per gallon 18.96128381

Full Tank Projection:
564.32247 Kms. ......... 341.3031086 Miles

This is all city driving with a heavy foot. The biggest effect on improved gas mileage for me has been the installation of new plugs and front left O2 sensor. Still not as good as others on this forum but a heck of a lot better the the 400 kms. I was getting before...

 

um ok, that equation is the dumbest thing ive hear yet on this forum, what if i have 8 foot wide tire? tire presure and weight wont account for that will it? go study physics so more

 

99 5 sp GXE,stock wheels (15 in steel w/ cover).I use sometimes the cheap gas and other times the 93 staff.What is interesting is that I got up to 428 miles on a tank ,with the cheap gas.I do little city driving and most highway. It seems a little crazy but I think that I get betteg gas mileage if I DONT use the cruise control.There is no gas mileage improvement ,but the car runs a bit smoother with the good gas. So I decided from now on to use only the good gas.Is maybe $ 3 in difference,(not enough to get a Mickey D meal). I do thik that the tire pressure has something to do with the mileage. I keep my at 32 psi all around.
About inflating the tires,I agree that the more PSI you get,the less traction you have. Also,the overinflated tires wear fast in the middle,so everyone can do as they please.

 

That's the major problem... some people are reporting miles per tank. What's a tank.. when the needle hits E? It could be 14 gallons on one fillup and 17.5 on the next. We have to report miles or kms per gallon to make any comparative sense.

 

Well, now, Mr. Smartypants-who-must-have-studied-a-lot-of-physics-in-your-18-year-life, you can't just shoot down an explanation without providing a better one. So what's yours?

 

I got 17.46 mpg city/highway. (20% highway) I KNOW this is horrible... Tires are inflated properly, new plugs and air filter... list goes on...

 

However....


The force of friction is directly proportional to the downward force, so the patch size isn't really relevant. You have a bigger surface area, but each unit of surface afrea carries less weight, so the frictional force stays the same.

F = Nu (where F is the Friction Force, N is the Normal Force, and u is the friction coefficient- which is constant)

Also, why does friction direction matter? The contact area remains the same, so what difference would it make what direction the car is travelling?




Also, the manuals for my 99SE and the manual for my 95GXE make no mention that these cars were designed to run on 91 octane fuel. They say that you might notice performance increases with higher octanes, but that it doesn't really matter what grade you use. Why does everyone think we're supposed to run 91+?

 

I tend to agree with you on that under certain driving conditions. If the road has inclines /declines, I have noticed that the cruise control tends to give a lot of throttle to get back up to speed. I sometimes just rest my foot on the gas pedal with c-c on and it amazed me how much the throttle position changes- sometimes more than 50-60% pedal travel. If I am looking to set a mileage record for my max - I'd probably stay away from cruise control, otherwise it probably won't make that much of a difference over a long cruise on the highway.

 

Because those 0-60 times and power rating of 190 hp and 205 lb-ft of torque weren't measured using regular gas. Simple fact is, the VQ was designed to use 91 or better octane. It can use 87, but it has to adjust to conditions which are not optimal for it.

Read the manual again, My 98 says to use 91 for best perfromance, however, you can use 87.

DW

 

I get about 330 miles on the trip with 93 octane refueling with 2 gallons left, and that's ragging the **** out of my car city driving. I haven't checked my tire pressure since I bought the car..it has the valve stem pressure indicator...and it reads good pressure....good enough for me=)

 

Understood. But 87 is not going to harm your car in any way... that's all I was saying. I will check my 99 manual again

 

No. You have it backwards.

 

Keys to getting the best mileage out of any car:

1) Keep it in good tune (all sensors, plugs, valves, fluids and filters in good condition)

2) Keep the tires inflated to at least the OEM recommended pressure.

3) Drive smoothly (no fast take-offs or jumping on and off the accelerator)

4) Shift at around 2k RPMs (use your right foot to control this with an automagic)

5) Use the cruise control whenver it's safe to do so

6) Use the OEM recommended octane fuel (for a 4th gen, at least 91)

 

The 1998 Maxima SE manual states on pg. 10-3:

"In most parts of North America, you should use unleaded gasoline with an octane rating of at least 87 or 91 AKI (Anti-Knock Index) number. However, you may use unleaded gasoline with an octane rating as low as 85 AKI number in those high-altitude areas such as CO, MT, NM, UT, WY, NV, ID.....Using unleaded gasoline with an octane lower than stated above can cause persistant, heavy spark knock. (Spark knock is a metallic rapping noise.) If severe, this can lead to enging damage. If you detect a persistent heavy spark knock even when using gasoline of the stated octane rating....have your dealer correct the condition.....However, now and then you may notice light spark knock for a short time while accelerating or driving up hills. THis is no cause for concern, because you get the greatest fuel benefit when there is light spark knock for a short time under heavy engine load."

 

Here is some highway data... this is really my first extended trip on the highway with this car. I was averaging about 80 Mph for the whole trip. I'm sure if I had slowed it down to 70 I would have extended the mileage. Still I'm very pleased.

Car Mileage Calculator
Enter Kms driven 615 .......... Miles 382.161
Enter Litres 60 .............US Gallons 15.852
Kms. per Litre 10.25...........24.10806207 Miles per Gallon

Projected Full Tank Mileage
717.5 Kms......................433.9451173 Miles

 

Altitude?

 

Coulomb friction theory is good under certain circumstances, but it doesn't explain tire traction very well. Contact traction of tires is very dependent on contract surface area, and some tires are so sticky they have a coefficient of friction higher than one, something that is not allowed under coulomb theory.

 

i totally lost wat we're talkin about over here ::confussed::

 

Yes it's confusing, I think the original discussion was based on improving gas mileage. Along the line tire preasure or increasing tire preasure helped mileage. Someone came up with a traction formula that has been a source of aurgument ever since. So we have a couple of discussions within this forum.

Hope this helps.

 

"The force of friction is directly proportional to the downward force, so the patch size isn't really relevant. You have a bigger surface area, but each unit of surface afrea carries less weight, so the frictional force stays the same.

F = Nu (where F is the Friction Force, N is the Normal Force, and u is the friction coefficient- which is constant)"

You're forgetting one MAJOR component. Internal friction inside the rubber of the tires themselves. When you have a flat contact patch area moving around a circular tire, you are going to get stresses inside the tire creating heat, hence the reason your tires get warm in the first place. Actual rolling friction due to the interaction of the rubber and the road produces relatively little friction when compared to the internal friction of the rubber as it flexes. This is where the energy goes when you lower the air pressure inside your tires.

Now, back to the orignal discussion. If you increase the air pressure in your tires, you have less contact patch area, and thus less internal friction and consquently higher gas mileage. However, since you have less of a contact patch area, you decrease your available traction and are more prone to peeling/sliding out/locking tires.

Don't believe me if you don't want to. It is the honest truth and has very practical applications.

For instance, if you are ever getting trapped in sand or snow, try lowering your tire pressure (in the drive wheels) by a good 5 to 10 PSI. It will increase your surface area and could get your out of that tight spot.

Race car drivers often alter their tire pressures by fractions of a PSI in order to get the traction balance just right. How do they change the traction on each tire? The formula I introduced early on in this thread that people for some reason have a real hard time believing (I don't know why, it works perfectly fine for NASCAR, CART, F-1, and Michelin). That formula is:

Load on tire = (pressure in tire)*(contact patch area)

Seriously, it really works. Its actually a fundamental formula in hydraulics:

Force = (piston area)*(pressure)

Just think of your tire as a piston that changes area when the load stays the same and the pressure changes.

The "Contact patch formula" is also the fundamental reason why you can have 35 PSI in your tires when it is up on the lift, and then drop your car down so it is resting on the tires and STILL have 35 PSI in the tires.