I know that many of you are tired of hearing me say that viscosity is the single most important property of any oil. It’s a mantra I learned as a rookie in the oil industry and one that I believe. The thing is, how do we know which viscosity is the correct one? For over one hundred years there has been an SAE standard, SAE J300, that provides a relatively easy way to help the end user choose. However, in most cases the end user needs guidance on what viscosity is right for their application.
I usually go back in time to lay the groundwork for my comments, but this time I’ll refrain. Besides, if you’ve saved your old copies of Lubes’n’Greases you can probably find one or two columns that go over viscosity in more detail. There is a story about viscosity that I would like to delve into that concerns the decrease of viscosity over the past at fifty years.
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When I started working at Pennzoil in 1979, the API category system was already in place. At that time, API SE was the current performance category. Unlike today’s API categories, no distinction was made about viscosity. Whether it was SAE 10W or SAE 50, the same performance limits were set. At that time, there was no real industry information about which oils were sold and which viscosities were popular. To top it off, do-it-yourselfers made up about 80% of the market. Do-it-for-me’s—those folks who had someone else do the work—were a distinct minority. Oil changes were done based on the famous (or infamous) 3-month, 3,000-mile interval recommendation.