Quote:
Originally Posted by Formulajones
Again, you have to look at the pour values if you want a real look at the cold operating temps. Not all 20w-50's are the same, not even close. If Butler recommended that viscosity for your engine, then go through the list and find your favorite brand that has a pour value that works in the climate you live in.
There are a few good 20w-50's that will work in extremely cold temps, and some of the 20w-50 brands are better in the cold than some 10w's in other brands because the additive packages are simply better with some brands. So it pays to look at the pour values.
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I think the pour values highly depend on if the oil is synthetic or mineral.. you can see it here:
https://www.youtube.com/watch?v=MVn5OzuHtjg
The advantage of a 5w50 over a 20w50 is that the 5w50 will flow a lot better when most of the engine wear occurs.. at cold start.. even if the garage is heated, the 20w50 will be outperformed by far. And when hot, both are about the same... but the 5w50 is synthetic, so it won't age as fast and it will not suffer from the heat as much as a mineral oil.
I'm also pretty sure that the synthetic types also have a better ash rating in most cases.