I have always used Shell gas, but something happened around a month ago where my gas mileage went from 32.9 MPG average, which I was loving, to 31.5 MPG average.

Yes, to me it is a big difference.

Driving habits, the same...

I even used some of the high concentrate Techron in a bottle thinking the fuel system was lacking due to debris. Well, it bumped up like .2 MPG using it.

I also thought my oil change coming up in 1300 miles 'might' be part of it.

The onboard computer has been telling me I am doing 31.5-31.7 MPG for the past month.

As soon as I went to QT Mart and used their 89 octane gas, the mileage as soon as I went two miles down the road went up a point, then another couple miles down the road another point wnet up and so on.

I guess either Shell has gone down in quality, put some additive in or is doing something my 2.2 Eco is not liking.

The reading currently is now 32 MPG, and I bet the drive home tonight will get me somewhere around 32.3 MPG.

By Saturday I should be back to my old 32.9 MPG average.

I think I am going to use QT Mart gas from now on, plus their gas is about a dime less than Shell.

I know never to use Mogas, and I stay away from that fuel even though it is sometimes even .18 less a gallon.

 

i havent noticed a change, but i know a lot of places are E10, so that could be why you are just now noticing, i didnt start seeing e10 labels on gast station until a few months back...i only run shell gas aswell, on both the balt and the cavy

 

my driving is erratic and i cant keep track of my mpg to the T like that. ill drive normal one way, be in boost 1/2 the time on the way back, drive only 2 miles tommorow. get gas at 3 different spots in town.

 

I'm the same...I'm in boost a lot, would take a lot to make my mpg counter change since I haven't reset it in a long time...

 

Yeah, if you reset your MPG meter after you fill up it'll go haywire when you accelereate up to speed. I like driving at 65 mph, throw it in neutral and reset the meter. Just so I can see me 99.9MPG

Avg for GM Stg 2 for me has been around 26-34. But if I'm on the highway and feather the throttle JUST enough so I can keep at the same speed I see 42-44MPG sometimes

 

Shell all the way for me too. Idk what my gas mileage is anymore. Never got the speedo recalibrated for my wheels.

 

I have not done a reset of the economy in 4 months.

One update I have, is that the noises I have been having with WOT which is more of a roughness is now gone.

Today I noticed that the excellerator is touchy. This worries me... there is a current post of someone that had his car have a bunch more up and go, but then had pre-detonations.
This damaged a ring and spark plug.

The car for no apparent reason, and in the heat, has a lot more response.

I have gone from 87 to 89 and 91 several times. I never noticed more than a hair more response with 91 octane. I also noticed my mileage would go down with 91.

I just hit 40k miles... someone rumored this a while back, that the computer changes over to a different program once you hit a certain mileage. The reason being, now the motor is broken in. Yes, it could be total bs. Sounds feasible, but...

Anyways, my mileage hit 32.2 MPG today. The roughness is seemingly gone.
But my steering has a small click randomly when turning; no way in *^(^ the axle is already toast. I don't romp on this car. Man...

This is turning out to be an odd car.

 

I always use BP and I get 32 MPG respectively. I reset the DIC every time I fill up, and also do the good ol' miles driven divided by gallons put in the car, and surprisingly the DIC is always accurate to +/- .3 MPG.

 

the click is either the crappy trim around the column (mine does it too) or the elec pws circuit breaker(auto reset)


i run shell 93 (:puts on flame suit and i see 32-35 in the city and around 38 on the freeway (average because i have seen 45-48 before) i only run anything else in an emergency..sunoco 94 brings it down too


i drive my car like i stole it and the cops are chasing me



any temps below 45-50 and my mileage goes down too..mid winter when its below 0 im lucky to get 30 on the freeway

 

Nothing wrong with using a gas with better additives, I only use 93.

When it is cold the air is more dense and the computer attempts to keep it at the same AFR by dumping more fuel. It may kill milage but it does slightly improve HP(a little... very little).