We should be getting our new Pirus (05, White option Package 6) in a week or two and we were wondering if anyone experimented with using 93+ octane VS regular? If so was there any MPG difference noticed? Our current vehicle uses premium and I notice with my Tundra if I use Premium the MPG increases. Seeing the Prius will use so little, compared to our current vehicle we were thinking of using premium in it as well, if there is a improvement over regular.
Higher Octane Fuel generally gives lower mileage because it contains less energy. It can also cause Emissions Errors and warning lights in the Prius because it can burn too slowly. Use only 87 Octane in the Prius.
Some have stated burn speed/energy content of gasoline is independent of octane rating. My worst tank of gas mpg wise was with premium grade. I see no need for higher octane in my Prius. Maybe a can of Techron on a tank before an oil change is the only gas 'upgrade' I'll do.
I can attest to the check engine light. It only happened when I used BP Ultimate 93. The dealer said I must have left the gas cap loose because they got an evap code. I think its a little too much of a coincidence though. I checked the gas cap and went through several days of ON/OFF before I went to the dealer to get it cleared. Some errors will clear after 3 - 5 continous restarts without an error. I do not know if this one is in that category or not. Anyway, just my $0.02. Larry