Poor MPG

1105 · Sep 28, 2004

last time I filled up my car, I put in 11.5 gallons and only got about 120-130 which equals somewhere around 10.5-11mpg. Before my gear swap, I was getting 100 more miles to the tank. Does this sound right? I dont beat on my car that often so I know thats not the problem, but I didnt think just gears would drop my mpg by that much. Anyone have any imput on this?

Killercanary · Sep 28, 2004

Just for comparison, I drove 120 miles yesterday and I only used a hair over a 1/4 tank... I get a minimum of 200miles/tank and that's when I'm hogging on it.

WhiteDevil · Sep 28, 2004

Wow thats crazy. I have 3.73s and i usually get around 200-215 miles per tank, if i drive nicely. If i punch it a lot then its like 180ish.

1105 · Sep 28, 2004

i'm getting about 30-40 to 1/4 tank. Paul... do you think my problem might be because I havent tuned my car yet or is there some other little things that are causing it to drop so low?

Venom351R · Sep 28, 2004

I just filled up last night w/ 230 miles on the clicker , thats w/ 3.55's and a blower.

Joes95GT · Sep 28, 2004

I hate give the stereotypical answer, but you haven't said when the last time the car has been "tuned-up". And this is an all of a sudden problem?

Joe

1105 · Sep 28, 2004

It has new plugs, wires, and cap... the fuel filter got changed about 10k miles ago, same with the rotor. When I had the 2.73's in my car, I would get like 250 to a tank, and when I swapped gears (but not the speedo gear) it would still read the same. Now that I swaped out the speedo gear for a 3.73 ratio, I can really tell how many miles I'm getting to a tank and its about 100 less.

Running 19lb injectors, 45psi at idle, 16 degrees timing if that helps any

Nik_95Cobra · Sep 28, 2004

My last tank managed 198 miles. That was with normal driving.

Yellow302 · Sep 28, 2004

i let her go to 220-230 before i think about filling up, ive gone as far as 260 and have 1 gallon left.

Mods in sig

Yellow302 · Sep 28, 2004

o my friend put a FPR on his truck and set it to 80+ and was getting 8MPG. I tuned it down to 40-42PSI W/O vaccum.

Increased power and gasmilage to over 22MPG.

revhead347 · Sep 28, 2004

That doesn't sound too good. I get 14 mpg around town. When was the last time you changed O2 sensors. Sounds like you have way too many mods for 19lb./hr injectors.

Kurt

95WhiteVenom · Sep 28, 2004

humm... I usually get between 260-290 a tank I got 300 once granny driving for a couple of days. I was averaging bout 16-21 last time I checked.

go-stang5.0 · Sep 28, 2004

Huh, thats about what I get...but thats city driving. If I get on the highway I get about 200+ mi. per tank. My milage pretty much doubles on the highway. I wonder if this is because my motor is untuned (surges and hangs idle at low rpms) or because my cam has a lot of exhaust duration and thats wasting gas. Maybe its the o2's, Ive doen two tune ups and havent changed the o2's yet. I just got my sniffer notice sp i may change the o2's before I go just for the sake of that.

Grn92LX · Sep 28, 2004

I get s-hit for gas mileage. Last time I did it, I got 15mpg with 95% highway Around town I got 10. Now i just changed my maf to a 30lb pro m vs the 24lb pro m I was using (with a remote optimizer to make it work) I changed my plugs and cap/rotor and added a 75mm tb. So far im about 100 miles to the 1/2 tank so we'll see if it improved at all. This tank was all around town miles. If that doesnt help, I might change my O2's and coolant temp sensor.

EpiKk3 · Sep 28, 2004

totally stock im making about 15 mpg city .. go about 220 on a full tank im thinkin

smokediver27 · Sep 28, 2004

Hey 1105, just for laughs, make sure 1 mile on the odometer = 1 mile. I know with mine, 3:73's with speed cal, Each 9/10's of a mile= 1 mile. Thus, I'm actually getting better gas mileage than what my Odometer is telling me. For every 100 miles my odometer logs, its missing 10. Check via the mile markers on an interstate highway if you have them.

DFG 5OH · Sep 28, 2004

I dont understand how you guys with engines all modded up are getting such good gas milage, and i'm getting really bad with a stock mustang gt. I get usually 12-17, but i never drive it in the interstate, just to school, and 10 miles to work. But i stay out of the gas most of the time, i run premium, and still dont get that good.

mo_dingo · Sep 28, 2004

matthiasj said:
I dont understand how you guys with engines all modded up are getting such good gas milage, and i'm getting really bad with a stock mustang gt. I get usually 12-17, but i never drive it in the interstate, just to school, and 10 miles to work. But i stay out of the gas most of the time, i run premium, and still dont get that good.

That is the first problem. Running premium gas willl hurt your gas mileage. I ran premium to eliminate pinging. Now that I 90% fixed my pinging, I run 87 octane, and my gas mileage is around 17-18MPG.

Getting good gas mileage is all about staying in closed loop, and making sure your oxygen sensors keep the a/f ratio at ~14.7. That is all you can do. If you put in a 160* theromstat (possibly too cold, and will still run the open loop), or you punch it all the time, then you can't expect great gas mileage.

smokediver27 said:
Hey 1105, just for laughs, make sure 1 mile on the odometer = 1 mile. I know with mine, 3:73's with speed cal, Each 9/10's of a mile= 1 mile. Thus, I'm actually getting better gas mileage than what my Odometer is telling me. For every 100 miles my odometer logs, its missing 10. Check via the mile markers on an interstate highway if you have them.

If you have 3.73's, and a 23 tooth speedo gear, then for every 100 miles your odometer, you actually only went 95. Which means when you calculate your gas mileage, you need to take 5% off of the mileage on the odometer, then divide it by the amount of fuel used. So you are getting WORSE mileage then you what your odometer is telling you!!! Sorry, just wanted to correct you on that point.
Scott

Grn92LX · Sep 28, 2004

mo_dingo said:
Getting good gas mileage is all about staying in closed loop, and making sure your oxygen sensors keep the a/f ratio at ~14.7. That is all you can do. If you put in a 160* theromstat (possibly too cold, and will still run the open loop), or you punch it all the time, then you can't expect great gas mileage.

Scott

Wrong. The 160* stat will NOT effect going into closed loop. Open loop to closed loop is TIME based. I do, however, think that running too cold can hurt mileage, but it will still get into closed loop. This is one of the next things im planning on trying to get better mileage. My car runs too cool at night and on the highway, so i'm gonna swap in a 'hotter' stat.

Found this fact on fordchip's site: "A colder thermostat will NOT cause your car to run open loop all the time. The engine goes closed loop based on time, not temperature. A colder 'stat may not make the car run much cooler unless you calibrate the electric fans to turn on sooner. If you have enough air flow (when cruising down the highway) then the engine will run cooler. Around town, in city traffic, it probably won't run much cooler without the fans turning on sooner. "

chefster · Sep 28, 2004

ya i a am gettin some 355s..currently at 308...it seems the faster you drive with the higher #s the lower the gas milage..i like to do 80 90 100 on my daily commute and found that my 410 was nut s and that a 373 would'nt be much better...ram air has helped alot withpower and gas milage

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