Ok as I stated in my other post I had a decrease in my gas mileage. I went and had it checked for leaks but no leaks. I am not getting a ses light so it would not be my 02 sensors, no dirty air filter. So what is next. Ive lost about 40 miles to a full tank of gas. Can anyone help.

 

Clean/Re-Gap Your Spark Plugs. If they are Burnt (brown) then replace them. If you are running Iridiums you Will need to clean them almost once a month (miliage dependant) as they foul vast. Put Some Fuel Injector Cleaner in your car.

You would be supprised on wow much a basic tune up will help that.

 

what gas you using? use the 89, anything above (unless your FI or have the PB) is a waste of money and apparently causes worse mileage

 

im using 87 octane. The car only has 17000 miles on them so is there a need for spark plug change already.

 

oh yeah, 87 is the one, my bad for mixing them up

for sparkplugs, you could try it. depending on the plug, i've heard people changing theirs every 10k miles cause of fouling and carbon buildup

 

i use iridium IV's and those suckers fowl like crazy...also, the larger fuel suppliers use a detergent in thier gas for fuel injected cars so i don't know how much the injector cleaner will help. it's definately worth a shot though.

 

I do my plugs (Denso IK16s) about every 10,000mi they do get burned pretty fast. Our cars run rich so if you drive in a lot of stop and go traffic then they are probably shot. I average about 30mpg in mixed driving mostly around town. As I get twords the end of 10,000 miles it will start to dip twords 28-27mpg. I drive like a grandma though.

 

Ive recently changed to a k&n drop in filter. IM gonna see if that helps any at all and may give the fuel injector cleaner a try as well.

Anyone else have an opinion.

 

bad oil makes the car bog a bit but i highly doubt it is that. how long has it been since your last oil change?

 

Im at about 2000-2200 since the last one. I use castrol gtx which is what the dealership used so I just stuck with it since I found a place that used it as well. They also include tire rotations in their oil changes as well so that works for me.

 

yeah i use that oil too, i'm not so sure about synthetic in my motor...switching gear oil over though....anyway that's off-topic, check your oil, check your plugs, make sure you don't have any exhaust leaks (look for carbon on the piping), and check your plug wires/coil packs to make sure you aren't arcing...otherwise i don't know what else to tell you...just ride with a lighter foot

 

another thing, if you're arcing you'll find a white residue on the bottom of the coils...it's pretty obvious if you see it

 

Checked all and all is good.

Also would the type of muffler have an effect.

 

bump.

 

not anything noticable. i've been through 3 different mufflers and seen no affect on gas milage...the only time gas milage decreased was when i put on a GT spec muffler and i developed a heavy foot since i liked the sound of it hahahhaha.....btw do you let the car idle for long periods of time before/after driving it? i noticed you live in houston, and i'm assuming it's hot there. idling to long when the motor is hot causes an excess of carbon build up in the manifold(s) and what not. i know this because i did that to my car in the begining of the summer...either way it's not beneficial to the car...something to think about.