[jEEd]

so i've been constantly getting 13mpg... driving hard or not... tested it over the month and not much difference between the two...

so i took my car to GRCperformance and had them inspect my car for some problems that could be affecting my mpg.. i was told i should be getting roughly 18. All i have in my car currently is... Exhaust and Intake.. the shop told me that this is what they think is the problem, maintence...

SPARK PLUGS
DRIVE BELT
TRANSMISSION FLUID
TRANSMISSION FILTER

he did clean my MAF Sensor which was REALLY dirty before he cleaned it and now my car doesnt run cold randomly anymore which is great, better throttle response,

and the owner of a porsche shop, SPECTRUMperformance ( has worked on many mustangs - Falken Racing), told me i needed to get it "tuned" (ecu or something) for my exhaust, i replaced it w/ 2.5" smooth pipes...

help please..

[Drgnracin72]

um you should see a little better mileage. i dont see why the tranny fluids would have to do but do need to be kept in check. spark plugs coul be a problems. run some injector cleaner through a tank. airfilter. shouldnt need a tune just for exhaust

[jEEd]

well he said the tranny fluid/filter needs to be replaced since they were the Original one on the car and hasnt been replaced he said it smelt "bad" like a sign to be replaced =\ alrite thanks DrgnRacin72

[jEEd]

this 13mpg stuff makes me sad and also when i see ppl saying they get 18-20 in my same model stang

[98GT4.6]

In town right? thats about what mine gets in town, 26 on the highway

[jEEd]

its actually overall 13mpg 1/2 city 1/2highway

[jEEd]

okay so i just talked to my dad, who is a ford mechanic expert, about what the shop guy said about my car and well he said we already replaced the sparkplugs and the drivebelt is fine on my car but i do need to service my transmission...(counldnt take my car to his shop since its pretty far)

so now im absolutely cluess about my mpg...

[68 dlxcoupe]

dont feel too bad mine gets about that but i have a slipping clutch and a bad tranny

[96Snaker]

13? Ouch man, well at least you don't have to run premium, right? lol, I do. But I'm getting consistant 19 city 24 highway mpg outta my v8 so my only advice would be just do a full tune-up on her and hopefully you'll see an improvement...
..oh and btw, tranny fluid always smells terrible, whether it's new or really really old. If you plan on changing it yourself wear a couple layers of latex gloves, trust me, you'll smell that crap on your hands for a few days. lol, at least that was my experience. Doubt old tranny fluid is hurting your mpg though, maybe 1-2 mpg but emphisizing the Maybe a lot.

Get a 4-wheel alignment next time you can, you never know. Tire pressure, etc etc, all really hurt mpg when incorrect. Good luck though.

[1998_svt_cobra]

Yeah but do you guys think a totally new tune will fix the problem? 13 mpg is a frickin big margin compared to what he should be getting. There has to be something major with what the heck is wrong with it.

[1998_svt_cobra]

I know! Maybe he has 4.56's in his rear end and doesn't know about it! lol

[97_4.6L_Stang]

i get 23 average between highway and city. . stock for 96-98 should be 17 city and 27 highay

[jEEd]

yeah its quiet ridiculous... well im getting my tranny fluid flushed n stuff next week... and i think im going to get it dynotuned or something afterwards..

my alignment is perfectly fine, did it not too long ago. what should i be running for pressure in my tires? i have 275/40ZR17 at about 44psi i think...

i would kill for 20mpg average =\ ........

[jEEd]

but yeah thanks alot for your suggestions guys really bums me out about my car and knowing its not how old the car is because it has really really low miles for my year, 39k when i bought it and now 50k-ish...

[96Snaker]

Originally Posted by jEEd 39k when i bought it and now 50k-ish...

Damn bro I'd stop drivin it and keep 'em low forever! Wow and I thought my 60K on my 96 was low, you bastard! lol j/k j/k

Does 44psi seem a tad too high to anyone else? I know on my tires it says never to inflate over 40, and I run 32psi on the street and drop it 10 for the track. But to what I said before, before you jump to the conclusion that you have something terribly wrong with the car, make sure you've got a really thorough tune-up (not talking dyno tune here, just simple oil changes, spark plugs, you know, etc etc) to rule out any and all "cheap" fixes. lol, if there is such a thing. Good luck bro and holy crap do you have a low-mileage car.

[jEEd]

yeah thanks its really awesome too but umm my tires say 50+ psi max or smoething like that =x so im not sure im at 44psi my boss told me to lower it a lil but he said it wont affect my MPG but it will help out the driving quality

[1998_svt_cobra]

Hey I think I know what's wrong with it. This is a slim possibility and I'm not quite sure, but I had a friend with a car that had the same problem. It was a really old Honda. It turned out that, I think , a cylinder wasn't firing. I don't know how the heck it could run without it, but it did and got horrible gas mileage. That may be your problem. All of the guys that have worked on motors have to back up this story first to see if it could really happen because I don't really remember what was wrong with my friend's car, but I think that was it.

[96Snaker]

Originally Posted by 1998_svt_cobra Hey I think I know what's wrong with it. This is a slim possibility and I'm not quite sure, but I had a friend with a car that had the same problem. It was a really old Honda. It turned out that, I think , a cylinder wasn't firing. I don't know how the heck it could run without it, but it did and got horrible gas mileage. That may be your problem. All of the guys that have worked on motors have to back up this story first to see if it could really happen because I don't really remember what was wrong with my friend's car, but I think that was it.

It'd be pretty hard to notice your car missing every 8th revolution of the engine. I dropped a cylinder in my probe some time ago, and while it would run ok (sorta), it was unmistakably clear that I had a misfiring problem. But yeah it kills your mpg not having all cylinders working correctly, that I can tell you from experience.
Jeed, if you are concerned about your engine's internal operating condition, I'd highly recommend performing a compression test on all your cylinders, as that would tell you loud and clear if there's anything gone awry. Really, everyone should do it once a year, kinda like getting a physical yourself, only on your car, lol.

[4.slo?]

check the spark plug wires at the coil packs. I was getting real bad gas mileage and finally got tired of it and checked everything, the throttle body was real dirty, get some b-12 and clean the inside of it with a rag, and one of the spark plug wires at the coil had some corrosion inside, I cleaned all of them and ever since the car is running alot better and it's up to 17-18 mpg, but I would like to see 20-22 on the highway.

[Casper98GT]

Wow....first off. Any of you know how to read youre door tag for proper tire inflation ????? 44psi!! It must feel like youre riding a rock. 32psi. Thats what you run. You dont set youre tire pressure relative to the MAX setting on the tire. You set them according to the door tag. It will say 32 FRONT and 32 REAR Spare 60.

If you had a problem with youre motor you would know it and you wouldnt be getting 13 mpg. Much worse trust me, i had a dead cylinder in number 8 a while back and not only did it sound like a POS, but it wouldnt move very well.

Its not uncommon to find corossion in the coil packs. Water gets in quite often. Just remove youre wires and use dieelectric grease on them. Then put them back together, clean them out of course.

Or just go with a kit like Screaming Demon has. Coil packs and wires for cheap money.


I only wish i could drive mine right now too see what MPG's i get....but then again i never cared much. Sometimes i have filled it twice in the same day.