One thing that respondants to the synthetic oil debate have not addressed is viscosity under different temperatures. While conventional engine and gear oils turn into a thick sludge when cold, synthetic oils remain much the same as when at normal temperatures. During construction of the Alaska pipeline, trucks used to be left running 24 hours a day because they were too hard to start when the engine became cold. Synthetic oils were later used, and the trucks were found to start more easily. Leaving them running all the time was no longer necessary. A good demonstration of principal is to install synthetic gear oil in a manual trans. You can actually feel the difference in cold shift pressure yourself, unlike engine friction. I used to have a hard shift problem when cold that was cured adequately by shifting to synthetic gear oil (not VW, but worked in both Alfa and Mitsubishi trans). Synthetic engine oils may under cold conditions be pumped up to operating pressure more quickly than conventional oils saving engine wear, regardless of what consumer reports says ..... I can't forget that my parents bought a 1959 Rambler based on their recommendations. Taxi cab engine wear is probably more a function of driver abuse than lubricant properties. And as food for thought, in a long-term experiment, my 1984 Mitsubishi truck which was run exclusively on synthetic oils and changed at 3K intervals has 140 PSI compression at 160,000 miles, the spec for a brand new engine (and no, it is not due to carbon in the combustion chamber!). DDF (Former chairman of Society of Automotive Engineers in San Diego)
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