Oil viscosity - why the 20W-50 BS?

My old factory manual for the 77 Gran Fury which was used for police use said for HD use run straight 30 or heavier oil--even in cold temps

The only thing between the crank and the bearings is a film of oil--why racing oil is still sold in straight 50 weights

Yes it does drag more, does put more strain on the oil pump shaft and might well not be needed in many cases but when the oil wedge is gone, bearing spin, cams go flat and things get ugly fast

The hotter the engine temps, the thinner the oil becomes.

Yes the "W" in ie; 10W-40 does mean winter and not weight like most people think. And yes this refers to cold viscosity not operating temp. The oils ability to thin out when cold was designed for low temperature starts.

Lighter oils like 5W-30 or 10W-30 are fine for most applications but I wouldn't recommend it for long trips in 95 degree heat on a high performance motor turning around 3000 + rpm steadily on the highway. It kinda turns to the viscosity of water from my experience. LOL!

Thanks, This say's it all. the BS is over W is winter? never new this. Learned a lot reading this. Thanks again. Steve

jimjimjimmy said:

http://www.enginelabs.com/engine-te...racing-oil-vs-street-oil-know-the-differences this is a good read on the subject

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