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I've read some posts (Salsa) saying that it's really a waste to put premium in your Vibe unless you own the GT. I thought for sure the fuel efficiency increased when using a higher grade. What about being a cleaner fuel for your engine (and the envionment) or being better for performance?Have any of you switched entirely to ethanol blend? Although it's octane rating is a bit higher and it's less 'harmful' to the environment, i hear it's not so good on the engine. Something to do with breaking down a certain seal. Thoughts?

Quote, originally posted by Zig in East Orleans »I've read some posts (Salsa) saying that it's really a waste to put premium in your Vibe unless you own the GT. I thought for sure the fuel efficiency increased when using a higher grade. What about being a cleaner fuel for your engine (and the envionment) or being better for performance?Have any of you switched entirely to ethanol blend? Although it's octane rating is a bit higher and it's less 'harmful' to the environment, i hear it's not so good on the engine. Something to do with breaking down a certain seal. Thoughts?Heard same thing but I have a base and use premium I noticed to get a little better gas mileage and performance on premium. Its also cleaner so a couple extra cents dont hurt my pocket.

You should put in the grade of gas which your engine is tuned to. For base or AWD, that is 87 octain, not 91 or 93. You will not get better fuel economy or higher performance, at least to any extent you can notice. Most of the time for a given company's gasoline, all grades of gasoline have exactly the same additives for cleaning. They just mention it with the premium grade in advertising.I am not an expert at ethanol, so I can't comment on that.Only good you do by paying for premium on base or AWD is that you are fattening the pockets of gas company and gas station, since there is no way it costs them 20 cents extra to produce premium vs. regular.

Here's a good thread on the subject. (There a bunch more, for anyone who has better luck than I do with the search function.):http://www.repairfaq.org/filip...E_002

I get 10-15% better gas mileage with plus. (89 octane) over regular (87) and if it only costs 5% more that regular, why not get it, it all works out.

Not arguing with you or your results, but technically it just doesn't make sense, unless the lower ocatane fuel you used as a reference point was inferior and not up to standard.

Quote, originally posted by Ding »Not arguing with you or your results, but technically it just doesn't make sense, unless the lower ocatane fuel you used as a reference point was inferior and not up to standard.According to the link MadBill posted I found this. So I guess its all possible.... If you are already using a fuel with an octane rating slightly below the optimum, then using a higher octane fuel will cause the engine management system to move to the optimum settings, possibly resulting in both increased power and improved fuel economy

I get best mileage from the midgrade as well. I have compared gas now from at least 4 gas stations in two towns (multiple tanks each time). I do not notice any performance from premium (at least my Vibe doesnt) but I do notice less gas mileage from premium. I get slightly better performance from mid-grade and usually 1-2mpg (max) out of mid-grade.Kinda off topic I guess, but goes with the comment above about not noticing a difference: My 99' Silverado V8 full size extended cab Z71 not only gets better gas mileage on premium, it gets one heckuva performance boost on premium! It is easily noticeable when I run premium through it, either 1 tank or 3-4 tanks!

yeah, but reading SCC or any other tuner mag, first they indicate better performance with higher octane gas compared to Cali gas(even when tuned on Cali gas) and in one article they indicate that gas types difere from one region of the US to another. I'll stick to premium till it starts to really hurt my wallet.

I've heard that if you switch gas types you'll have to flush out the fuel in your tank before putting in a different oactane of gas. Any truth behind this or is it safe to switch in mid-tank?

You can switch at any time, you will just get an octane rating averaged between the two. (Some stations selling 3 or more grades just have two storage tanks and blend them together for any intermediate grades)

I have always used the midgrade with ethanol in all of the cars that I have driven. I have never once had a problem. In my opinion why pay more for gas than you have too, the engine on the base is tuned to run 89 octane so I don't see too much reason to use 93. Unless you enjoy spending more money at the pump.And as for the ethanol hurting engines... That was mostly happening to foreign cars when ethanol first came out. The manufacturers were not aware of the problems that might occur with a fuel they didn't fully understand. Given the time I am sure they have fixed those problems cause you never hear anything more on the subject.

Thanks MadBill, I wasn't sure about that one