Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site watdaisy.UUCP Path: utzoo!watmath!watnot!watdaisy!gvcormack From: gvcormack@watdaisy.UUCP (Gordon V. Cormack) Newsgroups: net.auto Subject: Re: mileage and performance with hi-octane gasoline Message-ID: <7414@watdaisy.UUCP> Date: Mon, 16-Sep-85 18:48:34 EDT Article-I.D.: watdaisy.7414 Posted: Mon Sep 16 18:48:34 1985 Date-Received: Tue, 17-Sep-85 05:10:48 EDT References: <610@osu-eddie.UUCP> Organization: U of Waterloo, Ontario Lines: 34 > High-octane gasoline contains more energy per gallon than low-octane gas, > right? I mean, it accelerates better, hesitates less, and knocks very > little on Super Unleaded as compared to driving on Regular Unleaded. So a > gallon of it should drive my car further (more mpg) than would low-octane > gas, right? How much further? Enough further to offset the price > difference? What factors work into the equation? Do I need to be able to > change the mixture setting, compression, spark advance, or whatever, to make > a difference? Will the higher temperatures hurt my engine at all? > -- > Human: Bob Sutterfield > Facilities Management Division High octane gasoline will have no effect on an engine that runs correctly with lower octane gas. Every new-car owner's manual I have ever read makes this perfectly clear. If you are prepared to make engine mods, you can indeed get better performance from higher octane gas. The amount of power produced by your engine is roughly proportional to the compression ratio. If you switch from regular to premium, you may be able to use a compression ratio of, say, 10.5:1 instead of 9.0:1. This will give you more energy for the same amount of gas. Of less signigicance are some other changes that one may make. With higher octane gas, it is possible to run an engine slightly leaner without pinging, and it is sometimes possible to advance the ignition timing, which may improve performance. Buy the cheapest gas you can, so long as your engine does not knock. I don't think that any of the above mods, particularly timing and mixture, could possibly recoup the difference in cost. -- Gordon V. Cormack CS Department, University of Waterloo gvcormack@watdaisy.uucp gvcormack%watdaisy@waterloo.csnet Brought to you by Super Global Mega Corp .com