Bad gas mileage?

95Grandtouring5.0 · Jun 4, 2007

I have a 95 gt mustang, with just bolt ons. To be exact, 4:10 gears, bbk cai, bbk 70mm tb, Mac cat back. Those are the only Real performance mods I have that would affect gas mileage and my car is doing horrible. The car runs great, it doesn't miss a beat. The exhaust has a nice clean smell to it and no black smoke. Yet I find myself filling my gas tank up after 100-115miles and I always refill when its at 1/4 a tank. I never let it go below that. What could be making my car do so horrible with gas? I mean I know the gears do a good part, but most of the time I always short shift. So Im lost. Any ideas?

Magic · Jun 4, 2007

start with the basics, like a tune up (plugs, cap/rotor, fuel filter, air filter)...if that doesnt help, then check/replace the Oxygen sensors....
sounds like some pretty horrible mileage...

Paul · Jun 4, 2007

Is your EGR functioning properly? That affects fuel mileage.

scarface · Jun 4, 2007

I vote for the 02 sensors...mine were bad and I had terrible gas mileage.

95Grandtouring5.0 · Jun 4, 2007

scarface said:
I vote for the 02 sensors...mine were bad and I had terrible gas mileage.

Well a month or 2 ago i had clutch problems and I had to drop the exhaust and everything, mind you the gas mileage has been this bad since i bought the car. Anyway when we were putting the h pipe back up, we broke a 02 sensor and I went and bought a new one. I only had money for one at the time so thats all I could get. But I didnt notice any difference. I'm going to go to a shop soon tho and see if my car is throwing any codes.

Paul · Jun 4, 2007

Rather than spending all the money to take it to a shop to check codes, just buy a code scanner. They're only about $30 at Checker, and come complete with a book telling you what all the codes mean. Then you'll have it down the road.

MeanGrn Gt · Jun 4, 2007

definately needs a tune up. i was getting decent mileage (around 180 before id fill up). New fuel filter and some injector cleaner and now i get 220 normally. if highway miles i go about 240 and still have 1/4 tank left.

jared6180 · Jun 4, 2007

I drive my 94 GT with mods in the sig and 126k miles on it to and from work everyday(35miles one way) usually I shift at 2500 rpm, and I get on it at least once a day. The car needs a tune up but it still gets 20-22mpg on MOSTLY highway driving, I usually fill up at around 265-275miles on the trip odometer.

A previous Mustang I had did about 14mpg, I put in a K&N air filter, and new spark plugs, and wires, and the MSD Cap and rotor set at Autozone, ,and a new fuel filter, and changed to synthetic oil, and the mileage went up to about 20mpg immediatley IN TOWN! On the highway that thing did up to around 27mpg.

I plan to do the same thing on my current Mustang and I would advise you to do the same. No matter how many miles the car has it is my policy to make those changes now on every car that I own, i did it to two neons I owned, and all the mustnags I have owned except one.

CLIFFS NOTES: Get a good performance minded tune up!!!

95Grandtouring5.0 · Jun 5, 2007

Well the cap and rotor is a brand new msd. However the wires look a bit old so I will replace them with my next pay check, then a new fuel filter and I will have it taken to a shop. If I don't I'll buy 2 new 02 sensors straight up.

ripper · Jun 5, 2007

My 95 has been suckin up the gas too. Im gonna have to do the same. Good post :thumb:

Paul · Jun 5, 2007

You can do the fuel filter yourself! Get a Chilton's manual (or similar) and try it. You could do the O2 sensors too while you have the car up on jackstands. A fuel filter is something that a shadetree mechanic can do with no trouble.

Paul.

houston5.0jay · Jun 5, 2007

Um what if im getting the same thing and Ive done all those things?

I replaced both O2s... fuel filter air filter plugs wires cap rotor... and I still dont get crap for mileage.. AND!! the damn thing has 2:73s in it...

and I have a nasty WOT ping with 93 octane and weird temps as well..

scarface · Jun 5, 2007

check your timing, sound like it is WAY high.

SaleenStang94 · Jun 5, 2007

jared6180 said:
I drive my 94 GT with mods in the sig and 126k miles on it to and from work everyday(35miles one way) usually I shift at 2500 rpm, and I get on it at least once a day. The car needs a tune up but it still gets 20-22mpg on MOSTLY highway driving, I usually fill up at around 265-275miles on the trip odometer.

A previous Mustang I had did about 14mpg, I put in a K&N air filter, and new spark plugs, and wires, and the MSD Cap and rotor set at Autozone, ,and a new fuel filter, and changed to synthetic oil, and the mileage went up to about 20mpg immediatley IN TOWN! On the highway that thing did up to around 27mpg.

I plan to do the same thing on my current Mustang and I would advise you to do the same. No matter how many miles the car has it is my policy to make those changes now on every car that I own, i did it to two neons I owned, and all the mustnags I have owned except one.

CLIFFS NOTES: Get a good performance minded tune up!!!

idk about that.... stock 5.0s could not make 27mpg. thats very high. i have new(month old max) fuel pump, pulleys, cap, rotor, wires, o2s (bosch), plugs, fuel pressure regulator (40psi) and still only make 15mpg highway/city but i need a new tune and have every bolt on.