bad gas mileage ls1

**waylonSS** · 09-20-2006, 01:06 PM

hey i'm new on here, just got a simple question, maybe some of you have experienced this before.

I have a 2000 camaro SS ls1 about the past 2 months, the gas mileage has went to crap. like 14-15 miles per gallon. haven't changed driving style or anything else. the car now has 109k miles on it. everything else feels fine. plenty of power, runs like a top, smooth. i figure it may be time for a new set of spark plugs, factory delcos the best thing to keep it running well??

what else can make it get bad mileage, oh yea, car is 100% stock. no mods at all. what parts would be considered at tune up for this car? local parts stores here are clueless...

**Zboner** · 09-20-2006, 01:09 PM

NGK TR55's for plugs and new wires for sure man, and prolly a K & N

**2001NBMZ28** · 09-20-2006, 01:19 PM

No mention of any SES light, so yeah I'd do plugs and/or air filter if they've been in there a while. EPA sticker rated mine new at 18/26 (probably high).

**GatorSS** · 09-20-2006, 10:08 PM

Change your fuel filter, too, and add some injector cleaner to your tank while you're at it.

**cobrahunter** · 09-20-2006, 10:43 PM

14-15 miles? Is this city or highway driving? I get about 15-16 miles per gallon in the city. The LS1s come from the factory I think with 18-19 mpg city driving. So with all the mods that I've done, I wasn't too surprised that I went down 3 mpg.

**02z28ls1** · 09-21-2006, 04:37 AM

X2 on the city driving-maybe worse than that depending on how 'spirited' you drive. Mine will get over 30 mpg on straight hiway-but I don't get to do that much. So I'm happy with 16-17 around town.

**dbuie** · 09-21-2006, 05:58 AM

At 100K, I would definitely start with the basics such as those mentioned previously. Plugs, wires, air and fuel filters, replace differential and tranny fluids, proper tire pressure, SeaFoam in the intake and fuel tank.

**Frankthetank** · 09-21-2006, 06:03 AM

also pcv valve

**redz284u** · 09-21-2006, 08:40 AM

dont know about u, but its been hot over here 105-110F, and when i run my ac, my mpg go to 14-16 highway.....so maybe thats it.....

**02z28ls1** · 09-21-2006, 01:02 PM

I don't notice any drop in gas mileage because of A/C useage-it's believed to be because of the better aerodynamics with the windows rolled up. Your A/C would have to be dragging about 15 mpg to be that bad. I run the recommended 30 psi in the tires,sometimes 32, going to 35 doesn't register as any better mpg. The way you drive has more to do with your average mpg than anything else. Again-my car can get 30 mpg on straight hiway driving, 14-17 around town.

**1SICZ** · 09-21-2006, 01:26 PM

Bad 02 sensors=crappy gas mileage.....may want to check those...

John

**F-body fan** · 09-21-2006, 04:15 PM

I noticed a similar decrease in the mileage of my driver (a Toyota) ---- put in new O2 sensors, plugs, checked computer for codes, etc. ----- then I realized that I read once that bad gas (i.e. watered-down; leaned for low-smog; mixed with gasahol; and/or low-quality gas) can cause up to a 30-40% decrease in fuel economy.

Maybe our friends at ARCO and Shell are "cutting" our gas, AND gouging us at the same time...

**waylonSS** · 09-23-2006, 07:52 AM

thanks for the replies men!
i think some is up because the car has been getting 18mpg average city driving. then it went down to 15-16 out of the blue. it got freekin 23mpg on a 2 hour drive interstate in 6th gear. 93 octane premium is the only fuel it's ever seen. two of my friends both have m6 ls1's, one camaro, one t/a . both of them have gotten 31 mpg on long hwy trips. and the t/a is modded.

i got the stock delco iridium plugs for it. I figured the general knows what's best. i noticed that ngk has an identical plug the 55's, but had two different versions. like one with an x in the part number? anywho the stockers look the best quality to me. it's going to be a ball of fun putting these things in. I helped my buddy in the t/a replace his. we cussed a lot. and got cut up hands. but we got the damn things in. i'm going to do the fuel filter too.

as for wires? stock delcos are 118 bucks. accell 8.8 300+ race wires are 89 bucks. i'm gonna do the accells.

oh, almost forgot. is there a way to check the oxygen sensors if there not throwing any codes? one of them was replaced when I bought the car. do i really need 4 of the damn things? isn't there like mil's or something to delete two of the sensors?

**79JON** · 09-23-2006, 08:15 AM

My 98 TA has 130K miles and I run with the AC on all the time because I live in south Mississippi. When I got the car it would only get 14-15 in the city and 20mpg tops on the highway. It had really never had a tune up so I changed the Plugs, AirFilter, Fuel Filter, and a few other things. Now she gets 17 mpg in the city and the most ive gotten on the highway is 27.

**jmhvenom** · 09-23-2006, 08:26 AM

I used to get almost 30mpg with an A4 and 2.73 gears on the highway, then i realized it wasnt a civic and just made it fast lol

**1SICZ** · 09-23-2006, 10:43 AM

Originally Posted by waylonSS

thanks for the replies men!
i think some is up because the car has been getting 18mpg average city driving. then it went down to 15-16 out of the blue. it got freekin 23mpg on a 2 hour drive interstate in 6th gear. 93 octane premium is the only fuel it's ever seen. two of my friends both have m6 ls1's, one camaro, one t/a . both of them have gotten 31 mpg on long hwy trips. and the t/a is modded.

i got the stock delco iridium plugs for it. I figured the general knows what's best. i noticed that ngk has an identical plug the 55's, but had two different versions. like one with an x in the part number? anywho the stockers look the best quality to me. it's going to be a ball of fun putting these things in. I helped my buddy in the t/a replace his. we cussed a lot. and got cut up hands. but we got the damn things in. i'm going to do the fuel filter too.

as for wires? stock delcos are 118 bucks. accell 8.8 300+ race wires are 89 bucks. i'm gonna do the accells.

oh, almost forgot. is there a way to check the oxygen sensors if there not throwing any codes? one of them was replaced when I bought the car. do i really need 4 of the damn things? isn't there like mil's or something to delete two of the sensors?

As far as I am aware of the 02 sensor can go bad without throwing a code thus causing poor gas mielage. You just need to prolly replace the front two and then get 02 sims for the rears. You need to get Bosch 02 sensors at Auto Zone or Advance as they are the best for the money. I definitely would not put the stockers back in due to them not being gapped equally.......Just my .02

John

**02z28ls1** · 09-23-2006, 04:10 PM

It's my understanding that if the O2 sensors become slow + responsive the computer will throw a code. I don't see how it wouldn't-but maybe somebody can throw some facts on this rather than just their experience. Notice how everybody does a tune-up, and sensors at the same time , and gets his good results. I'm thinking it was the results of the tune-up. Could be wrong, any one with any LS1 Edit type facts here?