Date: Wed, 21 Apr 2010 11:53:55 -0500
Reply-To: mcneely4@COX.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dave Mcneely <mcneely4@COX.NET>
Subject: Re: Hose clamps..
In-Reply-To: <k2k6bc66ccf1004210728wa9f0273al3757611309a2d2c5@mail.gmail.com>
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---- Don Hanson <dhanson928@GMAIL.COM> wrote:
> I've recently run two tanks of premium fuel through my
> 1.8liter 8-valve Jetta/Golf motor now. One tankful was burned at some
> higher elevations and interstate speed..My fuel consumption remained just
> the same....23/24 mpg...as it normally is, using regular 'gas'. I 'think'
> the little 'Mouse-Motor' ran a little better on the premium and perhaps a
> bit cooler (though heat is NOT an issue with the inline) This motor has no
> knock sensors, runs the Digifant fuel injection system. So I conclude that
> regular gas is the best value, premium might be a waste of ca$h.
>
> Don Hanson
For almost all vehicles, the octane rating specified by the manufacturer is the one to use. Paying for "better" fuel is almost always a waste of money. A couple of caveats to that: (1) Alcohol has a lower energy content by volume than does gasoline. If non-alcoholic gasoline is available where you are, then one might parse the difference in price compared to energy content, and choose the non-alcoholic fuel if the difference in price is not greater than the difference in energy content. Volkswagen says to use non-alcoholic gas when available for the waterboxer engine, and I've tried to follow that recommendation. (2) In the higher elevations of the West, octane ratings on gasoline are low compared to in lower elevations further east. The reason has to do with lower partial pressure of oxygen in higher elevation (thinner) air, so reduced volatility, lower burn rates, and reduced knocking occur. The lower octane stuff burns just as slowly at elevation as higher octane stuff does at lower elevation. But, in keeping with the VW recommendation to use at least 87 octane, when the pump has a lower octane rating for regular fuel (I've seen as low as 85), I've paid for mid-grade or premium. Some have said that's foolish, because it is the lower volatility of the octane rating that matters, and 85 at elevation is as good in that regard as 87 down below. Bottom line is, if it doesn't knock in your vehicle, it's probably ok. But VW specifies 87 minimum, and I've gone with that. But when that was not available at a couple of out of the way spots in Utah and Colorado, the 85 octane stuff did not knock.
--
David McNeely
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