are you all sure I could use regular gas

Just for further encouragement...

I always have to test things for myself. Stick with 87!

Using SPSS for the statistics, I've come up with the following:

87 octane for six tanks: 53.6 mpg
89 octane for six tanks: 52.13 mpg
93 octanne for six tanks: 51.1 mpg

last four tank of gas; going back to 87 for good: 54.8 mpg!

All octane "tests" were performed using consecutive tankfulls, no additives. Oil changed, tires rotated during second tank of 89. Tire pressure: 42 front; 40 rear. 650-700 miles a week over hilly rural roads. Average speed: 45-55 mph. 20% city driving.

Chris

 

I live in western Montana, but go to the eastern part of the state fairly frequently. Over there most 'regular' gas is 85.5 octane. I use it in my Prius with no ill effects whatsoever.

 

Just as a side note, 85 octane is considered regular at high altitudes. An engine needs less octane at higher altitudes, due to thinner air (assuming normal aspiration).

Tom

 

Well, the owner's manual does not say use 87 pump octane gasoline only, it says use a minimum of 87, but don't worry at all, 87 should be just fine in your car.

Higher octane gas is not necessarily better, it just means that it burns a bit slower which is required the higher the compression an engine has.