Date: Sun, 07 Oct 2001 21:37:14 -0400
Subject: Re: 87 or 92 Octane in a 97 SE Turbo?

engines breath differently, most will cool better on the timing chain end. this is due to increased oil flow over that end of the engine. with a turbo the pistons and head run hotter specially when you really get into it. on the cooler side of the engine this excess "spot" heating causes the parts to become brittle. this is due to the metal fatigue resulting from "spot" heating in a cooler than normal area. use of high octain fuel furthur increases the "spot" heating thus the damage is increased. the idle control valve and the antiknock sensors should take care of the lower octain fuel, but if you want that extra boast use the higher octain. you must consider the long term effects though. that little bit of extra gives you quit a rush but you will pay the cost in the long run. if you don't believe me run the high test and keep your foot in it hard for the next five thousand miles. you will have to pull the head to repair the gasket or worse and when you do check the number one piston ( that's the one next to the timing chain end of the engine ) that piston will be white, the others will look like they should. the white will be due to heat stress and it will fail over time. most likly getting a hole in the crown. i know this is long but you seemed to want to know and you need to know all of the possible effects of that high octain fuel. Brian wrote: > I just purchased a 97 900 SE Turbo and I was wondering if octane is a > significant Turbo enhancer? The manual states that 87 octane is fine and > I've driven with both Super and Regular Unleaded and can't notice any > difference in boost or performance. For now I'm happy just pumping in > regular unleaded but I'm wondering if Super is really called for?

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