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Selection of the Right Motor Oil for the Corvair and other Engines
Introduction Click here do download the pdf file.
My object in this paper is to explain in common language how to protect your engine through the selection of the correct oil. In this explanation I will be summarizing various SAE Technical Papers with the information pertinent to this explanation. For those that are only interested in the short answer, you can jump to the summary. I will not tell you which brand to buy, but what to look for on the label. I will not repeat word for word what is in the pages of the American Petroleum Institute, but put it in the best lay terms I can think of. Some people will say that there are not enough graphs and charts, while others will say it is overkill. I hope to strike a balance.
Four main points are:
- Viscosity: How are recommendations determined?
- Viscosity: What happens in the real world?
- Viscosity Shear: The importance and effect of base oil quality.
- Additives and additive clash: What are the consequences of too much of anything.
- Sifting through spec sheets and the API classifications
Premise:
Many questions have been raised about the wear on flat tappet valve trains and other parts of Corvair engines by the reduction of ZDDP in the newer oils (API SM and CJ-4) and the desire to add commercial additives to increase those levels. Here we will investigate the advantages and disadvantages of these products and other items that affect wear.
This is the current draft of this paper. I’m sure there will be additional questions that will arise or points that I haven’t explained to the satisfaction of some readers. Please send your questions or suggestions to oil @ asboman.com (remove spaces) and I will answer them in the next draft.
The comments on oils in the US market are current as of April 2008. The comments on viscosities and the mixing additives are valid for all types of engines.
While I do not plan on frequent updates to this paper, as I add something I will note the major changes here.
- Significant additions to draft 7 include a few pages on xW-50 weight oils and their surprising viscosity curves.
- Minor additions to draft 8: Additional comments on “recommended viscosities”, flushing, used oil analysis and a few other items (as well as remembering to put my name on it).
- Minor additions to draft 9: A little more about additives and their dangers in the summary.
- Minor additions for draft 10: More myths busted.
Click here do download the pdf file. Current update is May 1, 2008
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