I've been talking with Fstanggt96 about some issue regarding MPG. he is getting around 13mpg, and would like to improve it...hopefully he will correct me on his mods LT, twin 60mm TB, CAI...and some other stuff with a tune.

I think his tune is off he normally shifts around 2200rpm which shouldn't make much of a differencebeween shifting at 1600-1800 like i do, and i get 22mpg city

 

I'd say you're right on the money with your observation, it's the tune!

I had a great tune loaded, was getting about 23-25mpg with all my mods. Had to load an "emissions tune" to get the car inspected, and I can actually watch the gas gauge move while I'm driving! I'm like WTF is going on here!? Tuner said all he did was turn all the emissions monitors back on, and I'm thinking they are totally out of whack!!

 

I get about 22-23 on the highway with bolt-ons, tune and 4.10s, dont drive on the city so can't give any input on that. How rich was the tune set and how much timing?

 

American Racing longtube headers and catted x pipe with weld-in Flows, Accufab twin 60mm TB, Drop-in K&N filter, SCT tune 91 octane perf(canned from americanmuscle), shorty antenna lol. Yeah, I had an economy tune before I had my headers installed and it was the same... Didnt notice a difference between that tune, this tune, or stock tune when I only had Flows and a K&N... The tune is for 91 octane but we have 92 in Washington, he said it would be fine. Mileage hasnt changed at all since I got the car in August lol. I made my exhaust video and got 108 miles out of the full tank, almost all city. Looks like I might get about 120 city out of this tank right now... Help! Lol, I didnt think much of it because hey, its a high perf V8 and these kind of engines suck gas. But If you guys are getting almost double what Im getting then I think something is wrong. Thanks for the help USMCrebel!

 

We get 16-18mpg in the city and around 23mpg on the highway in the '04Mach(STOCK). And 16-19 city, 22 highway in the '03 GT with 3:73s and add ons.

 

Since he states this was like with either tune and he lives in north western US. He might want to look at coolant temps, they should be around 190.

 

Living in your area I know what the problem is and or problems. First off it's all the damn hills around here. Second of all it is the tune. Before I updated my diablo tuner I was getting 15mpg now it's a little more but that's also the help of responsible driving. What kind of gas do you use as well, some contains more ethanol than others. The more ethanol a fuel has in it the more fuel it has to burn. I also wonder if your car has after market injectors....

 

Good point there with all the hills lol, I got a couple, I think we can rule out the tune though. Its always been the same case stock tune(Flows and K&N), SCT tune 93 oct. Economy (Flows and K&N), and now SCT Tune 91 oct. High perf.(LT's, catt-x, accufab twin 60mm, K&N Flows)... Stock injectors, I usually use either 92 octane Shell or Safeway gas, Same price and there close by. Both contain 10% ethanol.

 

Ok, best way I can explain this is about 2 ticks away on the cold side from exactly halfway if your looking at the gauge. When it gets there it stays there too, Doesnt move at all even when it was 106 degrees here for like 3 days it was the same unless you turn the car off and let it cool down lol.

 

Does your tuner show coolant temps when data logging or fan temp settings?. From your description of the gauge it seems to be in the normal range. My thoughts where maybe a stuck open thermostat and the slow raising engine temps causing extra fuel consumption.