jgilbs

I have an '03 Maxima automatic, and my gas mileage is bad - its averaging 15.9mpg according to my dash gauge. What does everyone else get? What are some things I can check that might be causing this? It seems to run fine, and the pickup is decent. I dont drive with my foot to the floor all the time. When I'm on the highway, I get 20mpg(if I reset trip computer while on the highway). All of this is not using AC. My pulley belt looks a little cracked, could this be causing my poor mileage.

VQP0WER

I don't think this topic has never been discussed before.............

Chris Gregg

iTrader: (59)

First, you need to understand how UNreliable the trip computer is at averaging your fuel economy. The only true way to measure this is by filling up, resitting your A tipometer, then filling up near empty (or 1/4 to 1/8 tank). Divide the miles traveled by the number of gallons used to fill up. That simple.

Then IF you are still getting that poor economy, you need to look at overall maintenance. NGK platinum plugs? What grade gas you using? Anything lower than premium will begin to reduce mpg performance. Several other things, but until you really verify the miles you are getting per gallon, I can't be sure you really have an issue. You should (in an automatic) be getting 330 miles per tank or more. I average 21-22 mpg. When I've run Lucas fuel additive (I get the big bottle)...I typically run 22-23 mpg on average.

Definately, do a search for some great references on this very topic.

fflint_18

I get just over 20 mpg around town running Plus. Jumps up significantly on the hi-way when I can run in 6th.

Car just turned 100k today (yippee) so I will be puttin in Iridiums next week and we'll see if I get much of an increase.

phatboislim

iTrader: (27)

probably a banana in your tailpipe

Amave

start with any dtc's, in the computer and go from thee...a full tune up couldnt hurt and dont ever go by the mpg monitor its not very accurate

Doomztown

I probably shouldn't do this but I will anyways:
Clean MAF
Clean Throttle body
PCV Valve
Spark Plugs
Tires
K&N Filter
Seafoam
Lighten out car load

AEMAXIMA01

iTrader: (3)

Check your tire pressure.

Specd_out

Tire pressure is the biggest culprit. Also if you havent done so do a tune up. Also depending on the mileage the cats could be clogged.

JustinXtlr

I have been having the same problem. I get about 200 miles to a tank. Brand new maf, and air filter,fluids every where, just had the tires worked on so pressures should be right. Anyone one got any ideas for me?

EDIT<and i have a new hi-flow cat still nothing.

jgilbs

Given the grinding noise coming from the driver's side, and the rough ring on my rear rotor, I'm starting to think it might be partially due to a stuck caliper (also have extreme judder when braking)

bullet187

Is your check engine light on? A while back I had a bad catalytic converter that caused me to get really bad gas mileage. After I got it fixed my gas mileage improved about 5 mpg.

ColdRain

regarding grinding noise and stuck caliper, shouldn't you be able to smell some burning after driving for while?
regarding bad cat, i believe you can drill hole pre and past cat to do pressure testing. search youtube on videos of such (user scottykilmer has good info).


p.s. is it just me or Post quote reply is gone?

Specd_out

the ones that will clog first will be the precats in the exhaust manifolds

JustinXtlr

Ahh good to know, I haven't even looked at that. How do I go about cleaning those. Or do I have to change the headers?

bullet187

Have you looked at your check engine light for any codes?

JustinXtlr

if your asking me, yes i have and i have no codes. ive checked numerous times.

bullet187

Since you have no codes your CAT is still good.

I would try all of these before I did anything else.

mandyfig

Tire pressure must be at least 34 psi. Anything less affects the rolling resistance, hence more gas burning.

JustinXtlr

my car has burned out a maf completely with throwing a code, and it has done that twice. i dont really trust my ecu.i think it might be a little slow.. but im still going to try all these like yall are saying.

thanks for the help!

jgilbs

Ses is not. Plugged in a scanner, and there were no stored trouble codes. Is a burning smell a prereq of having a stuck caliper? I don't smell anything, and the rotor doesn't feel any hotter than the front one, bout the outer edge of the rear rotor is scored, and very rough. Could this just be a bad pad?

bullet187

I would say your rear rotors need to be resurfaced or replaced and have the break pads looked at. It wouldn't affect your gas mileage though.

bad beat

if you have not messed with the TB check your vaccum lines for cracks. if you cleaned your TB a relearn procedure may help. I was having a mileage and other problems and I removed the cable from the positive terminal for aboutg thirty seconds. This causes the computer to reset. It helped the gas mileage a lot and also cleared up my other problems. my vaccum lines were dry rotted and cracked.