Thin oil
Thin oil
(OP)
This thread could have been started in the lubricant forum but it is more about engine design.
Almost all new car makers require really thin oils for their engines. This maybe because the oils and their additives are much better today or maybe because engines are manufactured with much tighter tolerance/clearance and larger diameter bearings (are they?)
So if new engines are designed to run on really thin oil, that means that new engines don't like or don't start in really cold weather? What's true, tight engines or thin oil fashion?
Almost all new car makers require really thin oils for their engines. This maybe because the oils and their additives are much better today or maybe because engines are manufactured with much tighter tolerance/clearance and larger diameter bearings (are they?)
So if new engines are designed to run on really thin oil, that means that new engines don't like or don't start in really cold weather? What's true, tight engines or thin oil fashion?





RE: Thin oil
Tighter tolerances, better additives, improved fuel economy.
RE: Thin oil
RE: Thin oil
No, there is a survival reason. It would run fine on straight 30wt in most climates. 15W50 might work in hot climates, but would be asking for trouble.
What's the point? Proper oil has always been important; it's just a little more critical these days.
RE: Thin oil
rmw
RE: Thin oil
RE: Thin oil
RE: Thin oil
RE: Thin oil
Advantages of thin oils are well made in this article http://63.240.161.99/motoroil/
Perhaps a 0W100 would suit everyone!
RE: Thin oil
Do I give up film thickness for those benefits in my car? No thanks, 30W please.
Pumps are bigger and bearing clearances are controlled more closely to compensate for the thin oil in new engine designs. Hot idle is the real test for those things.
RE: Thin oil
I know one thing, even if you can put heavier oil in a thin oiled engine, you never want to use a thinner oil than specified!!
Matthew Imbrogno
Mechanical Vollenteer - Arizona Railway Museum
RE: Thin oil
The guys who designed the engine should have matched the pump size to bearing clearance and oil viscosity.
I would expect that it is still relevant to adjust viscosity to ambient temperatures. Any advice to the contrary might be due to passing required tests under controlled conditions that do not reflect the true use variations in conditions.
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RE: Thin oil
RE: Thin oil
Sorry if I presumed that point and missed explaining it.
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eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Thin oil
Keep in mind that low temperature grades and operating temperature grades are different. At cold temperature it is the W grade that is relevant. Back when 20W's were recommended in passenger cars, OEMs usually told you to switch to a 10W for cold weather. Now most OEMs make it easier on motorists by recommending a single multigrade for year-round use- after all its hard enough to get the general public to observe correct change intervals anyway.
A 5W oil is about 11 times thinner (8% as thick) than a 20W oil at -15 C, but a 30 weight is less than twice as thick as a 50 weight at 100 C. So the cold temperature difference is huge.
Modern engine designs are actually easier to start in cold weather than older ones; this led the SAE to slightly ease the specifications for the CCS test for engine oils in 1999.