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<x-charset iso-8859-1>Hello- There's a lot of fallacies here... this is a long response, but should clear up quite a bit. > There has been a lot of talk about oils as of late. I would like to present a > few facts here. The VW air-cooled engine was built to run on 30 weight oil. That is a fact. The VW engine was also designed in the late 1930s :-). > Nothing has changed on this engine design since the engineers in the Black > Forest (I know, Wolfsburg is far from there, but Dr. Porsche was in Stuttgart > during the design back in the 30's) designed it for that single weight oil. VERY incorrect. A LOT has changed in oil technology. To understand what's going on, one must understand the temperature dependence of viscosity in an oil. For any given oil, you can make a plot of viscosity (i.e. actual real number, not some "index" number) vs. temperature. When they get hotter, they get thinner (i.e. viscosity decreases). This kinda sucks. In the ideal world, we'd like a lubricant with a CONSTANT viscosity. That way, the bearings can be designed around this number, and it's never too thin nor too thick. Well, back to reality: that's impossible. But, it does tell us what to work toward. In the early days of oil refining, they figured out that with their technology, they could make different kinds of oil all with semi-similar characteristics of temp vs. viscosity. They knew that they couldn't just put a plot of temp vs. viscosity on the back of every bottle as it'd confuse the hell out of consumers. So, they make a system. If an oil has a viscosity between A and B at 40C and C and D at 100C, we call it a 30 weight oil. Makes sense, right? Well, techonology got better. They could now develop lubricants that didn't have this extreme temperature dependence - they got less thick when cold and less thin when hot. This is GOOD!!! This means that oil is less thick when your cold and cold wear and tear is decreased, and it means that it is less thin when hot so hot wear and tear is decreased. They modified the existing numbering scheme: the first number tells what the oil does at 40C and the second what it does at 100C. A 10w-30 oil has a "10" at 40C and a "30" at 100C. And, technology got even better. Now, using synthetic base stocks, they could decrease the temperature dependence of viscosity even MORE when above 100C and below 40C. Unfortunately, the existing number scheme didn't reflect this very well, so they just called them "synthetic" and talked about all the good points on the bottle. Then came along hydrocracking - a new technology refining process. It allowed conventional petroleum stock to get temp vs. viscosity characteristics similar to "synthetics" above 100C and below 40C. So, to avoid confusing the consumers, they (Castrol) called these synthetic, although they were not truly synthetic. A legal battle ensued, and the result now is that the word "synthetic" means that it does better than normal above 100C and below 40C. > With that said, if you run a multi weight oil.... you are running oil weight > of the lowest number. if you use 10-30, you are using 10 weight oil. > Additives break down real fast in these engines so the multi viscosity stuff > does too. Wrong. Additives don't break down really quickly in these engines. You are using "additives" like a dirty word, but it is not. ALL lubricants, by definition, are comprised of base stocks and additives. And, in fact, on most oils, more money is spent on additives than on the base stock. And, furthermore, better anti-wear protection is given bang-for-buck on a superior additive package and a decent base stock than a superior base stock and a decent additive package. Case in point: Royal Purple oil uses excellent additives, but a hydrocracked petroleum base stock. BTW, FWIW, usually the cheapest additive packages around are used in straightweight oils... another reason to avoid them. > If you are running 20-40, you are running 20 weight oil. This > stuff is for modern engines not our beloved air-cools. Are beloved aircooleds like to run high oil temperatures. I like to have an oil that doesn't thin out at high temperatures and make my oil pressure light come on when I fall back to idle. Likewise I don't want this oil to be so thick that I have lots of wear and tear when the engine is cold (i.e. only 70F oil). This stuff is GREAT for our aircooleds. > I have seen several > engines die an early death from 10-30. Sounds like some misplaced blame to me. > If the pump is trying to pump light > oil.... cavitation happens. Do you know what cavitiation means? Evidently not. Let me assure you that cavitation isn't happening in your oil pump, even if the light is coming on :-). The light comes on when a) it is sucking in air or b) the oil is too thin to give enough pressure or c) the tolerances in the engine are too sloppy or too old to sustain good pressure. B is easily tackled by using an oil that's thicker when hot (multi-vis wins again). > If 30 weight was not used in our engines anymore, why does Castrol make a > great one. So does Kendal. So does Pennzoil. Because they are cheap. I don't buy premium synthetic oils for my lawnmower :-). I have done THOUSANDS of miles of testing with synthetic and conventional oils over mountains and through deserts with oil temp, oil pressure, and head temp gauges. Let me assure you - the "synthetics don't cool" stuff is 100% solid MYTH. Head temp never changes. Oil temp may go DOWN with a good synthetic oil. And, oil pressure is more steady with a quality synthetic lubricant. The only reason NOT to run them in a VW engine is economics. If you have no oil filter, you have to change your oil very frequently. Spending large amounts of money on synthetics becomes questionable for the average person. If you have a filter, you can typically extend the drain interval and make back your money. That's the only reason why. Take care, Shad Laws LN Engineering - Aircooled Precision Performance http://www.LNengineering.com ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/ </x-charset>