Fuel economy for 87 vs 91 octane gas

Old 12-25-2008, 02:21 PM
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Join Date: Dec 2008
Posts: 2
Default Fuel economy for 87 vs 91 octane gas


I was under impression that 91 octane rating for my Lexus RX330 (2005 model) should give me higher MPG compared to 87 octane gas. But I am somehow getting opposite results.

With 87 type gas, my car shows MPG anywhere between 18 and 23. While with 91 type gas, it shows anywhere between 14.5 and 18 MPG.

I want to know if it is usual to see lower MPG with higher octane fuel? If not, then what can be the reason for such change in MPG?

Merry Christmas and Happy New Year -2009.

Old 03-07-2009, 12:54 AM
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Join Date: Aug 2008
Posts: 27

Depends on what the engine was made for. If it's a high compression engine than you want high octane. I believe the some are made for high octane gas but can run on regular and advertise it as such.
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