mpg down after changing from 89oct to 87oct

i was getting around 25 to 26 mpg on the hwy when i was using 89oct. gas. i changed to 87oct after being swayed by my internet research where people universally said that premium gas was a waste of money. I have ran three tanks of 87 and my hwy milage has dropped to about 21 mpg!! could this be from the computer not readjusting to the 87? over 1000 miles seems like a long time to adjust. anyone else downgrade to 87 and see similar results?

 

I upgraded from 87 to 89 or 93 (depending on gas station/ethanol content) and noticed a significant improvement. Ethanol has had the most affect than any other variable in fuel.

 

my motor seems to like the more expensive juice too. don't second guess yourself - your own test results are better than any advice from the internet universe.

 

If you really wanna find out whether or not its saving you anything....Figure out the COST PER MILEfor each octane. That'll let you know exactly how much money you're paying PER MILE based on what your gas prices are.

For example:
Cost per gallon divided by the MPG will give you cost per mile.
Do this for each octane and costs involved.

 

Thats what I did and found that ethanol free 93 and 89 both got me to almostthe exact same price per mile as 87. I just have longer to go between fill ups, but I dont save or lose money

 

Shell 87

 

I would suggest going back to 89 for the next couple of tanks and see how your MPG is affected. After I installed my lift and wheels, I started to use Shell 89 in town, when I travel on the highway I use Shell 91.

 

The computer likely DID adjust to the reduced octane fuel -- by dialing back spark advance. The new ECUs ARE that sensitive.

My 2010 Taco (and Wifey's '09 Honda Fit, FWIW) runs much more smoothly on Shell 93 than the wonder water the dealer bought for the initial fill. I ran 93 in my Taco's predecessor because detonation demanded it. I use it in the Taco because it just works better.

 

i use shell or ampco 87 and always get 26-27 at fill ups i usually try to use one or the other and stay away from racetrack and places like that