electricsunset Posted May 17, 2007 Share Posted May 17, 2007 Have 97 Legacy Brighton 2.2 automatic with 81K miles and live in Calif. I know that the manual say 87 octane is just fine and that 91 octane is a waste because of the compression stats of the engine. With this said I seem to get 3 mi per gallon more with 91 octane versus 87 octane. This is local driving. The 3 mi per gallon for local driving pays for the $.20 difference between 87 and 91 octane. I drive with a light foot on the gas. Car is tuned up. Am I dreaming? Is this possible? Can 91 octane make a difference? Everything I read says that 91 octane for a car like this is a waste as far as improving mileage. thanks Link to comment Share on other sites More sharing options...
lawl Posted May 17, 2007 Share Posted May 17, 2007 If you fill up with shell, I think they put better stuff into the 91 than the 87. Specifically V-power or whatever it is. They also claim higher gas mileage on 91. I dont doubt the validity of this, as I'm sure additives can make a difference. However... what's the point in getting 91 if the difference between 91 and 87 is $1010210213023 dollars? You won't save any money getting premium over regular, even if you get better mileage with premium... car for sale. PM me! Link to comment Share on other sites More sharing options...
chenc544 Posted May 17, 2007 Share Posted May 17, 2007 My experience with my local Shell gas is that I do get better mileage with the V-power 91 as oppose to the other station's gas. I usually get around 1.5 mpg better. I get 25-26 mpg with other station's 91 so the Shell gas gives me 5-6% better mileage. As long as Shell 91 is less than 5-6% more expensive, I'm better off getting the Shell gas. 91 octane is about $3.35/gal here right now. So even if Shell 91 is $0.20/gal more expensive I'm still breaking even and I don't have to stop at the gas station as often. The moral of the story is to do your own calculation and figure out where the break even point is for your situation. Link to comment Share on other sites More sharing options...
b4wantab Posted May 17, 2007 Share Posted May 17, 2007 Odds are you are dreaming. In a N/A Subbie the ECM can't advance the timing enough to take advantage of the octane. 3 mpg seems like a lot of gain. With that being said I do notice better mileage with shell than the others so that is all I use. I have also noticed smoother running with the shell's mid-grade (89) verses the regular (87). I atribute it to Subbie's over-active knock sensor so I just use 89. I will have to try 91 just for S & Gs sometime. If you search around you will notice a lot of variation in mileage for the same cars. More variation than you can really attribute to driving style. If you do the calculations and you get 3 mpg more, go for it. Peace, Greg Link to comment Share on other sites More sharing options...
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