Possible Mileage issue problem.

[DavidPIL]

Hi all...Ok, i've read and participated in several posts here regarding poor MPG issues. I've said my piece about ethanol and different gas companies but now I think I've run across another possible problem.From Illinois, I traveled to South Carolina. 2 fill-ups in my GT with an average of about 31-32 mpg through mountains and all. I was happy, the Vibe was performing flawlessly till I fueled up near Columbia SC. about 20-30 miles down the road after pumping 93 octane Exxon, I noticed a slight whistling sound in the engine. The engine seemed louder as well and had a noticable loss of power. I thought I had over-worked the engine cuz it was after about 10 hours of driving.I noticed I hit the 1/4 mark much sooner than I had the previous 2 fill-ups. (about 86 miles when previously I was getting 120-134 miles at that mark). I was very worried.I then decided to put in a "octane booster" from an Advance Auto. Filled up the little less than 1/2 tank. Mileage was 23.6 all highway and mostly flat. About 10 miles after the octane booster, and an over-night rest, the engine sounded fine. Lots of daily Myrtle Beach city driving, more aggressive than I normally would. Checked mileage after the next fill-up and recorded just over 27 for agressive city driving. I was relieved.Drive home, the Vibe was once again great. had a bit of a head wind after the mountains yet still averaged 31.9 over the 950 miles.Could some of these gas stations be putting lower octane than listed in their tanks? This was a single hose pump, could they have the pump wrong where they pump a lower octane through the premium setting? Is there any way to verify the octane we actually are getting throguh the pumps?!?! THis might have been an isolated incident but I did notice a lowered performance level after pumping Philips 94 Octane at a local station. I dunno but it sure concerns me if this is a possibility especially since our cars NEED the higher octane.Dave

[teammonkeys]

Could be... I heard of stories where they pumped the wrong octane gas into the gas station tank.