Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site zehntel.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!houxm!ihnp4!zehntel!cjohnson From: cjohnson@zehntel.UUCP (Chris Johnson) Newsgroups: net.auto Subject: Re: Multi-Viscosity Oils Message-ID: <1609@zehntel.UUCP> Date: Thu, 27-Sep-84 12:48:18 EDT Article-I.D.: zehntel.1609 Posted: Thu Sep 27 12:48:18 1984 Date-Received: Sat, 29-Sep-84 08:35:42 EDT References: <131@umcp-cs.UUCP> Organization: Zehntel Inc., Walnut Creek, CA Lines: 35 The standard *high* temp is 220 deg. f. This is important because one of the major problems with Multi-Vis oils is that as the tempurature varies *outside* of their intended range they tend to break down faster than the corresponding single viscocity oil (ie. 10w30 is worse at 230 degrees than straight 30 weight.) In a water cooled engine this isn't that important because the engine basically won't heat up over 220 degrees, but in an air cooled engine temps can reach up to 250 degrees in worst cases. This is especially important because as the oils viscosity drops the oil pump doesn't work as well. I owned a VW bug with a *very* tweeked engine and found that 30 wt oil heated to a point that the engine would regularly vapor lock due the temp in the engine compartment (it is especially strange to have dual carbs with one vapor locked). I switched to 50 wt racing oil (Valvoline) and the problem disapeared. Analysis: If you own a water colled engine use a multi viscosity oil if your climate is severe enough to require it. (30 wt oil is *very* thick at 0 degrees) If your climate is constantly 40+ degrees use what you want. Don't use single viscosity 10wt or 20wt oil unless you live in -20 degree weather AND your car never heats up to operating temp.(ie. you use it for short drives only.) If you own a air colled engine use the highest viscosity oil you can *for your climate*. Change your oil's weight if the weather cools during winter. DON'T mix oils of different weights. The thicker oil will sink to the bottom of the oil pan and just sit there, inhibiting cooling by providing an insulating layer (esp air cooled). DON'T mix synthetic oils and standard oils for similar reasons. Slipperily yours, Chris Johnson