Can't figure out my gas mileage problem :(

[makavelius]

Hi Everyone:

I have a 99 camaro with 150k miles on it. Never had any problem. Just a month ago had the SES light go on for the spark plugs going bad so I changed the plugs and wires. What I can't figure out is for the last few months I am getting about 280 miles on one full tank when I use to get about 360 miles. I've done the following in the last 2 months:

1. New plugs/wires.
2. New pcv valve
3. Two new O2 sensors (in exhaust manifold)
4. New air filter
5. New fuel filter
6. Fuel system cleaning from Jiffy lube to remove carbon etc.

I don't have any SES codes going on or off to make me think something else is wrong. THe only thing I have never done is clean the throttle body. Do u think that might be the cause of the prob? Any thing else u guys know of I should do. Always do the oil change regularly too at 3k miles.

Thanks for any suggestions.

HR

[CamaroRob97]

The things you have done it should be running good, you even did a top engine clean.

Is your car warming up as it shoud normal? If not it would take you longer to get to closed loop which means running rich longer. You do have your egr correct?

Overall your gas mileage ant bad at all compared to some peoples, but have fun.

[NoRiceInside]

i have a theory...STOP MASHIN ON THE GAS! lol.

[V8 Killer]

Well...Depends on how you drive mostly...Dont hotfoot around and see how your mileage is from there.Is your car warming up good? A cold engine uses twice as much gas.Whats your operating temp when your driving?

By the way

Check the EGR

[makavelius]

Hi:

No I don't have a lead foot at all. Just drive regularly. The temperature seems to be 210 degrees and sometimes its around 195. I don't know why it fluctuates.

As far as checking EGR, how would someone whose not too mechanically inclined do this. Should I take it in to the shop to have them check it?

Thanks

Haseeb

[V8 Killer]

Well that is a good temperature...I really cant tell why your mileage has gone down.Maybe your Gas gauge or Trip Odometer are a little out of whack.

As far as the EGR.Your best bet is take it too a shop and have them check it,However if it was bad it should be giving you an SES light so thats probably not it.Try running a bottle of fuel system cleaner.

[Need4Camaro]

I don't mean to accuse you of overlooking the simplicity but whens the last time you had an OilChange?...

I get anywere between 325 and 390 and I didn't do half of what you did... infact I'm betting the plugs in my car are still stock plugs and I've got 130K on her... Not even the clogged airfilter robbed me of my gas milage but I replaced it anyway...But just as a theory... your cat just might be going... ALSO check your tranny fluid...

[makavelius]

Thanks again for all the ideas. I did an oil change 6 weeks ago and I do my oil changes on time so it can't be that. Tranny fluid was changed about 40k miles ago. I guess I could try that or like you said maybe something with the CAT but not seeing any SES codes. I will take it to the dealer to have them check out the EGR and see if they can find anything.

[V8 Killer]

Did you ever have the differential fluid changed?

[00firebird]

i only get about 260 all city..

[camaroincal]

How much pressure are your tires inflated to? This can make a significant difference in gas mileage. I like mine about 35 psi cold all around. If you are under 30 your gas mileage is probably worse than it should be. Also, weather can be a factor. If you have been driving in very cold or foggy conditions then you may be getting a bit worse mileage than normal.

[HeadyFirebird'00]

I AM LUCKY TO GET AROUND 300 MPG. THATS LATELY, i DRIVE A LITTLE CITY AND MORE OPEN ROAD AND SOME HIGHWAY. ITS WEAK SAUCE. COMPARED TO Y'ALL 360IDIDALLTUNE UPS POSSIBLE, EXCEPT FOR THE EGR. HERE IN ILLINOIS THE WEATHER IS F'IN COLD. SO DONT FEEL BAD IF UR GETTING AROUND 300. BUT DO FEEL BAD THAT IT HAS GOTTEN WORSE.

[Need4Camaro]

My best milage was 380 to a 15.5 gallon tank... 96% Freeway miles of speeds bouncing between 45 MPH and 80 MPH... ran into rain twice, ran into a traffic jam, had to exit multiple times for my sisters smoking habits (atleast she respects my car)... and I was by ALL means NOT easy on the gas... I was also overdue on an oilchange but we all get the point... I could have gotten better I suppose but I love my gas milage...

[dorkins]

wow...
i get a whopping 200 miles per tank...
wtf...
compared to you people getting 360, mine sux...

no mods as of yet, 57k miles, just got it from dealer, should have new oil???

im in NE ohio, so its kinda cold.. but this last week of nice weather, and mileage still sucked!

got about 230 with 89 octane...
any advice?

[V8 Killer]

Dont use 89...use 87..thats what your engine was meant for.Check your tire pressure.