i think i figured out my mpg right.....i went 450km on the weekend and that was a fuel tank of fuel so that's 279 miles our trucks hold 26 gallons of fuel...sooo.

279 divided by 26 = 10.7 WTF is wrong with my truck or am i figuring it wrong??

mods 91 SC tune
magnaflow exhaust
CAI

 

you should have divided the exact galllons you put in when you filled up. unless you ran out of gas and filled up

 

my light came on then i drove about 12 more miles......it was close enough to being out....

 

Have you thought about replacing the EGR valve and cleaning the TB things I am going to do because I am only getting 11.4mpg and used to get about 13.2mpg and larger tires do not account for all of it but if any other helpful hints I would like to hear as well

 

i just replaced all the spark plugs and cleaned the erg valve along with cleaning the throttle body....not a change. I have stock gearing the 3.55s or whatever and the stock tire size....i should be getting damn near 18 i would think. I could drive my old lifted 454 chevy and get better millage.

 

Your light comes on when there are only 5 gallons left in tank.

 

Time for a tune up by the sounds of it. When was the last time you cleaned the TB, cleaned/repaced the EGR, added new plugs, cleaned/changed the air filter or CAI, got your oil changed, reset the computer?

 

Keep in mind this 10% ethanol crap is less efficient and can cause a loss in mileage. My 460 Ford gets less than 4 mpg now. But that does sound a little low for a Hemi try adding it up again next time you fill up and remember how many gallons you put in at the pump and try to figure it up when it's at the same fuel level as when you filled up to get it as accurate as possible.

 

Just before i did this trip i put synthetic oil(mobil 1) in...changed all the spark plugs for some ngk, cleaned the throttle body and cleaned the egr valve...my air filter was just cleaned and oiled(k and n)....what could cause this??? it was on cruise most the time also so i wasnt flooring it around here and there.

 

My light comes on and it only takes 22 gallons at that point. Ur doing ur math wrong you didn't use 26 gallons to go that far. It doesn't matter if the light was on I would bet money on u only put 22 ish gallons in. Tune up won't hurt u but ur prolly getting around 15 ish