My gas mileage has gone down the drain..suggestions?

[TheGr8Schlotzky]

I remember back when I got the car, I got 29mpg one tank 70% highway with several WOT runs. Recently, with about a 55/45 blend of highway, I calculated 18.9mpg. This was with a very light foot through the whole tank, and some drafting at 55 behind semis.

I've just got intake/exhaust. Clean air filter. I've replaced the plugs with new delco iridiums, new wires, new o2 sensors, tire pressure is equal at 32psi, replaced fuel filter, I seafoamed a while back through the tank and vacuum system, and the alignment is good. None of the brakes are dragging and the car coasts just fine. I don't have a cat, and I'm not throwing any codes. I'm maybe 20-30 pounds over stock.

I'm out of ideas to get the gas mileage back.. What else could be causing this?

[ViperRider]

Re: My gas mileage has gone down the drain..suggestions?

http://forum.camarov6.com/showthread.php?t=88459


A lot of things mentioned there, but seems like you should be getting great mileage considering how well it sounds like you maintain your car.

[97rs4life]

Re: My gas mileage has gone down the drain..suggestions?

I reopened this thread, but for future references all gas mpg threads are going to get deleted as we have tons of them already with answers. This one might be unique, we will see.

You going to the same gas station? Are they adding more ethanol to their gas?

Engines get tired, mpg is going to drop over time

[TheGr8Schlotzky]

Re: My gas mileage has gone down the drain..suggestions?

Thank you.

Oregon passed legislation starting the first of the year that caused gas to go to 10% ethanol. I understand this will affect mileage, but I don't feel that it should drop my mileage so drastically.

Regarding engine age, that's understandable as well, but it's been maybe 6k miles since I was getting 29mpg, and this was before a lot of the maintenance.

Oil changes have been 3000 miles or less with new filter. EGR and PCV seem fine, and even assuming a minor problem with either (nothing to set an ses) I wouldn't think it would be responsible for such a drop.

[IwannaCamarosoBad]

Re: My gas mileage has gone down the drain..suggestions?

idk man my friend is having the same problem with his but his engine is over 200K (Close to 210 if not over by now) and his has dropped a little he says but he's still getting good mileage for his car, He has sprung a leak.

Maybe something is clogged? or beginning to clog? ....... I'll swap engines with you LOL 3.4 LOL nah, idk bro ..... hope you get it fixed though

[95astrovan]

Re: My gas mileage has gone down the drain..suggestions?

yea, like ^^he^^ said, when i got my car back in june i was gettin an average of about 27, believe the actual number was 26.8. My last calculation was 19.3 w/ no change in driving style, no change in highway/city, gas station, nothing. clean filter, plugs and wires are in good condition. If you're feelin' a little less power lately, you may have the same problem i'm facing, which i've pretty much narrowed down to a head gasket failure between a couple cylinders. I'm losing water at a pretty substantial rate also, thou. Hope ya figure it out man, this is a bad time for these F-bodies to start craving more gasoline...

[TheGr8Schlotzky]

Re: My gas mileage has gone down the drain..suggestions?

I recently did a coolant flush but I wasn't and am still not losing any coolant. Power seems to be there, though I don't floor it much at all. I'm at 125K on the clock, nothing too low, but nothing too high either.

[TheGr8Schlotzky]

Re: My gas mileage has gone down the drain..suggestions?

The only thing I've noticed is that the car never really heats up past the 1/4th mark on the temp gage unless I'm sitting in a traffic jam in warm weather, when it will raise another 1/8th maybe but stay under 1/2. Either way, it's been like this since I bought the car, so no change there since I was seeing nearly 30mpg.

[IwannaCamarosoBad]

Re: My gas mileage has gone down the drain..suggestions?

The only thing I've noticed is that the car never really heats up past the 1/4th mark on the temp gage unless I'm sitting in a traffic jam in warm weather, when it will raise another 1/8th maybe but stay under 1/2. Either way, it's been like this since I bought the car, so no change there since I was seeing nearly 30mpg.

I think you might have something clogged or pinched off in the engine bay. Maybe in the Fuel rail? (Forgive me if I have it wrong I am a n00b to internals or everything except the intake for that matter lol)

[95astrovan]

Re: My gas mileage has gone down the drain..suggestions?

hmm...that really stumps me bro, but yea, keep a close eye on ur coolant. My leak literally came out of nowhere...at the randomest time, just after i had topped off with coolant, one day it ran hot and suddenly i have this HUGE leak. i believe it started back in december, bout a month after the mileage started falling. Now i gotta fill the radiator every 4 days or so. But like, i said, best of luck dude

[IwannaCamarosoBad]

Re: My gas mileage has gone down the drain..suggestions?

hmm...that really stumps me bro, but yea, keep a close eye on ur coolant. My leak literally came out of nowhere...at the randomest time, just after i had topped off with coolant, one day it ran hot and suddenly i have this HUGE leak. i believe it started back in december, bout a month after the mileage started falling. Now i gotta fill the radiator every 4 days or so. But like, i said, best of luck dude

Maybe he has a rat clogged in there somewhere (Like in meatys story :P) I honestly dontthink being a little over stock weight would effect it greatly to make it drop almost 12 MPG.

[95astrovan]

Re: My gas mileage has gone down the drain..suggestions?

Power seems to be there, though I don't floor it much at all.

well then, next time ur out on the highway, try n stretch it out one good time. If it feels a little fatigued, it might be somethin internal. referance point, I used to never have to go past half-throttle to pass cars runnin 65+ on the freeway. now i'm pushin close to half-throttle just to hold 60. Your's might not be that bad, but it could be the start of something.

[bigbrian442]

Re: My gas mileage has gone down the drain..suggestions?

Has your car been tuned? Have you put a lower temp thermostat in it? If it's not running at 195 with the stock fan settings that will affect fuel millage. Might be time to replace the T stat.

[Rob Bell]

Re: My gas mileage has gone down the drain..suggestions?

I agree with Brian, I would check the thermostat. It should be about 195 or so. On mine the temp guage is close to 210 which ain't accurate because our gauges suck. But at least it's consistent so I'll know if something's up when it happens.

[TheGr8Schlotzky]

Re: My gas mileage has gone down the drain..suggestions?

The car has been tuned but nothing regarding fan settings, just torque management, shift durations and removal of the cat code. I haven't put a lower temp t stat in, but I do feel that the car should be running warmer. But like I said, it was running at the same spot on the gauge when I was getting 29mpg. I'll replace the thermo and see if that changes anything.