Gas Mileage


New Member
Jun 28, 2004
Bay Area, CA
I just Picked up this 1992 LX 5.0, It has a rebuilt 302 with only 1,000 miles on it. The Car has 167K. I have been driving it around town but mostly on the Highway and it only seem to get about 185 miles to the tank which equals out to about 15 to 17 miles to the gallon this seems pretty bad. My last 5.0 got at least 220 miles to the tank. Do you guys have any information or ideas that would help me get better gas. By the way I have 3.08 gears, and everything is stock on the engine, and the engine runs really strong. Could it be the fuel filter? Any input would Help.
Thanks :shrug:
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185 miles on one tank is about 12 mpg. the tank holds 15.4 gallons. and this is bad gas mileage. im getting more than 270 miles per tank on my stock 89 AOD conv. and thats about 60% city.
do a tune up
welcome to the boards!
couple things i would check: ECT, ACT, and lambdas. each can be out of calibration and causing you to run rich, while never tossing a code. i.e. your ECT is telling the puter your car is cold when it is warm. this equals rich, but the value (sayin the motor is cold) is within specs, so no code.

you really need to calculate the milage when you fill up - a little bit of guessing or a crappy gauge can be misleading.....
good luck.
My car gets about 13 mpg. That is why it's been sitting an awful lot lately. I've found over the years that any kind of city driving in the Mustangs really kills the milage. That's why I have a Focus now.
Do yourself a favor, fill up the tank to the top. Push the trip odometer button on the dash or write down the actual odometer reading. Go for a 100+ mile cruise on the highway at no more than 70-75 mpg. Then go straight to the gas station and fill it up to the top again. Take the number of gallons added at the last station and divide it into the number of miles driven. This is the only way to be sure what mpg you are getting. If not at least 22-24 mpg, start trouble shooting.

I have an essencially all stock 5.0 w/160k (factory 3.08 rears) and get 26-27 mpg if I keep it under 70-75 on all highway driving. although my numbers may be slightly off because my speedo is off by 5mph at 70. Figure 5 is 7% of 75
so take away 7% from 27mpg and come up with a more acurate 25.22mpg? I think my math is correct.

Anyway, do the test and find out for sure what your mpg is before changing everything under the hood.
Good luck.
k12 said:
Anyway, do the test and find out for sure what your mpg is before changing everything under the hood.
Good luck.

good point, but there is no need to replace parts needlessly. pulling codes and even if no codes are found, checking values on a few sensors will likely help with the milage (knowing sensors are out of whack, or giving peace of mind that they check out alright). cost is free if he has a DMM.
THanks for the Info Guys. HISSIN50- what exactly should i be checking when you mean ECT, ACT, and Lambdas. I have a code puller is that what ya mean by DMM? I checked the Plugs and they look good, no signs of Fowling.
DMM = digital multi meter (a volt meter). i like digital for most things (sans TPS checks, mainly).

the ECT (engine coolant temp) sensor and ACT both have values warm and cold. i dont know if a parts store manual will have the specs - i do know that Jrichker has been kind enough to post the numbers in the past (he might post them again, but if not, try searching his posts for the numbers). im pretty sure he did not long ago for Smockdoiley....

the sensors can be out of calibration. so say the ECT is telling the puter that the motor is cold when in fact, it is at 200* - the absolute reading from the sensor is within spec (no trouble code tossed), but it is not correct for the situation.

the lambdas should have a run of like 0.1 to 1.0 volt, IIRC. you can check them to see how they are reading (lower voltage is leaner, higher voltage is richer).

i bet J.R. and others have better ideas and info for you, but this is what came to mind at first blush. now if all the sensors were replaced when the motor went in, you can probably forget all of what i said.

good luck.