terrible gas mileage.. whats up? modifications maybe?

[apzak]

my gas mileage is terrible. I topped the tank off with regular hess gas.. good stuff not cheap gastation crap. Anyways i reset the trip gauge and i only got 330 miles on a full tank of fuel. edmunds.com says i should get 378 city and 480 highway. half my driving is highway driving so it should definetly be better than 378, and i get 330. Not only that, when they filled my tank they filled it all the way (piping and all). I don't know if edmunds does this, but i'm sure my tank was filled up to the gas cap because it was above "F" for a while so there was gas in the pipe. When I went in for more gas when I was empty it read "331" on the trip. What is causing this bad gas mileage?

I have the following modifications:Hotshot headersInjen Cold Air IntakeApexi N1 exhaust

Could it be my engine breathing alot easier, meaning it needs more gas so the ECU is giving it more gas?

Something else that I think is causing the bad gas mileage is the ground that connects to the catback. Mine ripped off when some dumb mechanic let the catback drop while replacing the leaking gasket, but he and other mechanics told me this ground cable is useless. Well, if it is useless why did Nissan put it there in the first place? Should I order another ground strap or not even bother and give my car a tune up? It's just turned 55,000 miles and the only things I changed is oil, oil filter and tires.

I bought my CAI used and anthony bought it new so I dont know how old the filter is. Anthony if your reading this, you think I need a new filter now?

[gabossie]

Hmm...I have the same problem right now. I went from getting 400 miles to the tank to barely scraping together 300, and it seemed like it happened all at once. It was also about the time that I got my catback and the ground strap tore off. That really doesn't seem like it should cause a problem though. Anyone have any ideas?

[NeverEnuff]

what size tank does a s14 have? my s13 gits around 350 to a tank

[WingsNThangs]

what size tank does a s14 have? my s13 gits around 350 to a tank

How many miles on the engine and what kind of modifications do you have?

[crzycav86]

Wow.... I get 200-250 miles per tank. And I usually fill it up at the 1/8 mark... I guess lead foots dont help. And this is on a stock car.

Anyway, your exhaust mods should only raise your gas mileage. The exhaust work will simply let you accelerate faster and allow you to get into 5th gear sooner.

The CAI may slightly hurt your gas mileage, since technically, its increasing volumetric efficiency due to the denser intake charge, although it shouldn't hurt mileage very much.

Its probably your lead foot....(if you have one)

[driftaholic]

i usually get about 250 a tank in city driving. i got 360 once on 99% freeway

s13 with 130k and intake and exhaust

[Hellion240sx]

um all i have is exhaust and i only get about 300-330 miles to a fulll tank. i use chevron 89 or 93 sometimes i notice a diff when i use each. also it could be the way you drive as stated b4. o btw never use shell gas. i went thru a full tank in less than a week. do the tune up and try new air filter then post again.peace

[apzak]

when you guys throw these numbers at me, how do you know how much gas you burned? do you let the needle to go "E" and assume that's where it was when you filled it last time? or do you actually check the tank and write down how much gas you filled in the first time, then check if it matches the second time you fill up?

[driftaholic]

i almost invariably get right around 12.5 gallons when i fill up, so my numbers are for 12.5 gallons

[Structure240sx]

i think our tanks hold jsut about 15 gallons

[TachyonS14]

S14 tank = 17.1 gallons.

[driftaholic]

S13 = 15-7/8 iirc

[apzak]

TachyonS14 - OT but damn!!! thats a steal! I was checkin out your car domain website, I paid alittle more that twice that for my 98. how many miles did it have when you bought it? Very nice deal, specially from the original owner. where did u find it? autotrader?

[aznromeox]

I'm going to check my timing today to make sure everythings right. I've tested the last 4 tanks. I get 14 MPG

The engines rebuilt. All I have is intake. I don't really care for the motor as long as it gets me through december.

[DarkStar]

I'm totally stock right now (except for ignition wires) and I get about 30mpg I'd say.

[TachyonS14]

apzak - Yeah I searched autotrader for MONTHS and left the lady like a billion msg's and she called me back and I swooped on that shiat. Btw the mileage is 100k which is high, but she drove from Yucipa to San Diego everyday so they are all highway miles.

[MainEvent212]

it's all about lead foot...

my mini cooper s calculates gas mileage. and i average 17.5

this is supposed to get like 25? lol it's cuz i drive w/ a lead foot, i'm never just coasting, either accelerating or braking...too A.D.D. to just chill out

[NoBottleJustThrottle]

i got about 200miles on a tank of gas in my K20A2 powered Civic...that has an 11 gallon tank...and i was in VTEC all the time.

[Phax]

i'm never just coasting, either accelerating or braking...too A.D.D. to just chill out

:withstup

[Hellion240sx]

everytime i fill up oi reset the little trip meter thingy. but recently i have been filling up only about half a tank ($10) and i got about 170 or 180 miles, with some lead foot driving. heh yeash a.d.d.

[Altiman94]

change your o2 sensor. You wouldnt believe the effects it has on mpg.

[Altiman94]

i got 200 even on my last half tank.

[POS_S13]

try changing your fuel filter, it should fix your mileage problem

[I am Technoman]

Another issue with the HS header and the o2 sensor is that for some reason HS puts the bung hole for the front o2 sensor "the most important one" on the back y pipe. This is no good. The ECU can only read the two back cylinders and can NOT read the front two. So that means the ECU is getting one half of the gas.

this can cause Bad fuel milage and on my Nissan the o2 stop working all together.

This was my fix. I found the harness to the front o2 coming from the ECU and I cut it so that I could make an extention harness about two feet longer. So I solderd the o2 harness plug to my new harness and solderd it back the the orignal one where i cut it. Now my front o2 is where the back one should be in the collector and the back one is in the front bung hole not plugged in. My car ran so much friggen better after i did this compaired to how HS waned me and everyone else to do it.

Sorry about my spelling I have had a few beers!

[hoffmantaj]

I was getting 30 miles a gallon for the first few monthe I had mt s-14...I took a trip the other day and I only got 24... I fill up all the way before I leave. When I get there I fill up again and divide the miles of the trip by the gallons to filll back up...I can't explain the drop....I'm gonna try a new 02 sensor..

[cheez80]

i get about 13-ish mpg

sr, catback, gutted cat, 3"dp, intake, z32 fuel pump/filter, etc.

[Japican]

I've also realized that my stock '90 240 is gettin less gas mileage. I was gettin close to 260 on almost full tank, but now ill be lucky if i can get over 200. Theres gotta be somethin wrong, but if u guys r gettin well over 300 im scared

[TachyonS14]

I get 20 mpg city driving w/ some "spirited" driving, and the a/c on all the time. I bearly drive the freeway, so my highway mileage is still unsure. On another note, I found out for the first time that my low fuel gauge works, only I still had 1.5 gallons left... oh well.

[hoffmantaj]

I used to get over 350miles a tank in my s-14, now I'm scared to test it.....Will my fuel light still work if my gauge does not???

[WongFeiHung]

Intake and exhaust should only help gas mileage because are not 'power-adders' they 'release' power by increasing effeciency...

Check plugs, plug wires, cap and rotor, o2 sensor, air filter, fuel filter, timing...