The "Wing Doctor's" Comments on oil


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Tag: oil

Re: oils, by Nelson Quimby "The Wing Doctor"
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From           "NQ" <[email protected]>;
Organization   Elso Graphics
Date           Sat, 17 May 1997 23:00:22 -0400
Newsgroups     fj.rec.motorcycles
Message-ID     <[email protected]>;
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One of the most frequent questions I'm asked is "what's so different about oils and what should I use?" When people have a question they seem to get as many opinions as they can, which in the case of oil, only adds to confusion, because there are so many opinions. Well, I want to give you some of the facts about oil.

One statement I hear quite often is "oil is oil is oil, it all comes from the same place and is packaged by somebody else". For the most part this statement is absolutely correct, since a lot of the finest brands of oil started out as Pennsylvania crude oil, (Pennsylvania crude being one of the best). What makes one crude oil better than another, you ask? The better crude thins the least as it's temperature rises, but that's not real important right now. What is important is, "motorcycle oil vs automobile oil". The differences are the additives that are used, both in quantity and quality. The oil you put in you car is perhaps 10 to 20% additives. Yet a specially blended motorcycle oil can be 50% additives. One of the more apparent (cushions things like transmission gears) additives found in both types are polymers, (multi-viscosity additives). We all know that oil has a tendency to thin out as it gets hot, this is where these polymers come into play. Probably best described as thin (microscopic) strands of plastic. Have you ever heated a piece of plastic and watched the results, well if not, the plastic curls. And that is kind of what happens to these polymers, they expand and curl causing the oil to actually thicken as it warms up to counteract the thinning of the crude base.

Now polystyrene-type polymers found in most automobile oils don't have a lot of strength and will be 50% sheared, or worn out, after only 2000 miles in a car engine. So you can imagine what kind of shape they would be in if they where exposed to hundreds or thousands of pounds pressure between transmission gear teeth. With that, the polymers in motorcycle oil must be shear resistant and can cost 10 times more than those used in automotive oils. This brings me to another very important additive, extreme-pressure additives.

Theory of lubrication is to maintain a film of lubricant between two surfaces thus preventing metal-to-metal contact and metallic friction. Though the polymers help in this area polymers alone can't survive all of the squeezing and shock loads of a transmission and camshaft lobes. So that's where the additive "ZDDP" or "Zinc Dialkyl Dithiophosphate" comes in to play, (Can you say Zinc Dialkyl Dithiophosphate?) Don't feel bad, I had a tough time with this one. I don't even pretend to be a chemist. But I do know that zinc, being a mineral, clings to the metal surfaces so when all else fails the zinc will protect the surfaces from direct metal-to-metal contact. Now the phosphorous, an essential element in ZDDP, is limited by law in oils marketed for automobiles because the catalyst won't survive when confronted with the phosphorous. But since motorcycles don't have catalytic converters larger quantities of ZDDP are added to quality motorcycle oils.

Are you confused yet? These are the two biggest differences and most costly to distinguish motorcycle oils from automobile oils. It's safe to say that all motorcycle oils are somewhat of a synthetic blend. Obviously some more than others depending on other additives.

If your totally baffled by all of this, don't worry about it. A good rule of thumb is use motorcycle oil for motorcycles, automotive oil for automobiles and aircraft oil for aircraft. Simple as that.

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