my tune is on..Term did a great job, and like i said, its better than before i was tuned.

I was trying to get a miles per full tank guys, so posting up 25-35mpg doesnt really tell the whole story of a full tank of gas, but if it was like that, it would be 300-400 miles to a tank...

 

25 mpg x 12 gallons = 300 miles and about a gallon left over so you don't run out of gas.

30 x 12 = 360. I did 380 once before.

 

I'm not saying your tune is off, but if your on some sort of E-blend your injector seals may be giving out

 

to continue on though, I never really run a FULL tank through the car so it never needs the 12.5 gallons.. i always fill up when it gets under or around 1/8 tank.. that said it still seems odd how your numbers are still that low... tuned or untuned, when staying out of the throttle you should be getting decent mileage.. just matter of thinking what could be the issue here

I use the "myCars" app n heres my current numbers if these trends mean anything to you and your driving habits

Average since buying the car in April:
27.77 MPG

BEST:
#1 93 oct, 10.91 gallons, 347 miles, 31.79 MPG over 2 days, 95% HWY
#2 93 oct, 10.79 gallons, 332 miles, 30.76 MPG over 1 day, 95% HWY

WORST:
#1 91 oct, 10.49 gallons, 250 miles, 23.83 MPG over 10 days, 10% HWY
#2 91 oct, 10.43 gallons, 252 miles, 24.17 MPG over 7 days, 30% HWY

 

thats excellent^^^...my car is nowhere near that, and like i said, i am on only the best 93 gas...
my vacuum seems fine at -16 with a/c on and idle, and -22 when driving. i keep boost @ 5psi or less since i shift at 3k rpms...Dunno what the issue is, but obviously I need to start troubleshooting...i'm gonna start with the fuel filter and make sure the purge solenoid is still good too, since i have replaced it 3 times in 12k miles!!! isn't there another solenoid in the rear of the engine too???

 

They are within 2% of zero everywhere. His car was showing very good mileage when cruising when we were tuning it. I drove it some and at 60 MPH in 5th it was seeing 36-38 MPG.

 

yea there is a vent solonoid back there as well

 

Just out of curiosity, have you noticed anything wierd with his cam positions in the logs by any chance? Like fluctuations, static position, or not fully going to a commanded position?

 

I see part of the problem. I read the word "boost". If you want good mpg, keep it out of boost.

 

omg dude, no **** keep it outta boost, like i said it was mostly out of boost but sometimes gets up to 5psi....lol, common' man...haha

So, i am gonna replace the vent solenoid, purge solenoid, and fuel filter to start...

 

I'm running a Term2 tune since labor day and my mileage is over 300 a tank full. I'm not light on the gas pedal either. There is no way I'd believe the tune is bad.

I don't know how a restrictive/restricted fuel filter would do it. I'd lean toward the latter two.

 

Yeah those purge solenoids can cause bad mileage. One of the HHR SS I tuned gained 5 MPG when he swapped his purge solenoid.

 

Not that I noticed.

 

Well it says you "keep boost at 5 psi" lol. Can't read minds.

Not sure if this has been mentioned yet, but when was the last time you cleaned / changed your air filter?

 

Just a guess, but do you think boost/vacuum leaks would be the cause of your poor gas mileage? Running rich? You mentioned you were down on power.

 

My dic says 24ish mpg. That's all around driving for me though, boosting, highway, town. I went to Punxsy Saturday and Sunday and was averaging 34ish mpg all highway.

 

Yours speaks to you? ****, my dic just spits at me.

 

My DIC reads 20.2 MPG but it has to be off. Im getting more like 26 mpg and i have a really short drive my AVG speed is 22mphs

and this is gms1

 

I get between 27-30mpg driving to and from work...it mostly long roads no lights but stop signs..especially driving around base..its kind of hard to explain.....got 32mpg coming from Sacramento couple weekends ago and I had to some serious up hills...like had to downshift uphills...range on fill up was 400+

 

do you mean driving loads as in stress on drivetrain components or drivings loads as in demand from the engine?

 

drum roll.

 

I have very similar problems as you Aaron. My mpg has just recently dropped to about 22 and I'm getting about 195 to a tank. I was going to clean my k&n this weekend to see if it helps. Let me know if your find anything else. I hate burning through sooo much gas.

 

Think my car avgs 28 mpg. I can get about 3 full days, round trip. I drive 55 miles one- way so... it's hard to stay off that boost! It keeps calling me! lol

 

28 mpg with hhr trifecta.I take less fuel on trifecta vs gm tune(27).

 

Haha. Aren't you a funny guy.