Originally Posted By: Tony10s
Originally Posted By: demarpaint
Originally Posted By: StevieC
My choice:
Going by your pour point chart 5W20, 0W30, 5W30, or 0W40 have the same pour point. So in theory, there's no benefit in cold weather starting right down to -50F, using that chart as a guide. And no point in these discussions.
You noticed that too, demarpaint. If one goes by the pour point in that chart, there is no real differentiation amongst the oils you mentioned, lol.
Pour point is just not a good way to judge the cold performance of oil in an engine...Amsoil was nice enough to provide CCS test data in that table and we can't even bother to read it??? I wish they gave us MRV, too, but having CCS is great compared to the big nothing that most PDS give us.
The Amsoil 5W30 has a somewhat lower CCS viscosity at -30C than the 10W30 has at -25C...from my American point of view, the 5W30 extends the starting range down by 9-10F compared to the 10W30. Normally an oil will about double in viscosity for every drop of 5C at these low temps, so you can also roughly think of the 5W30 as having half the viscosity of the 10W30 at extreme cold.
Looking at the 0W30 compared to the 5W30, we could expect the latter to have a CCS viscosity of about 2X(3968cP)=7936cP at -35C using the rule of thumb given above...this would fail the 0WXX CCS requirement (as it should given that this is a 5WXX) and is also 48% high than the 0W30's 5372cP at -35C. This is despite the oils having the same pour point.
What's the cost of using the 0W30 compared to the 5W30? Well, the 5W30 has a 2.1% lower NOACK loss (absolute, not relative) going by Amsoil's results and also has a slightly higher HTHS...if you're in an area that's never going to see -35C barring the Earth going off its axis, you could argue that the 0W30 buys you nothing positive and possibly gives you less high temp protection and a higher danger of engine deposits. Similarly with comparing the 10W30 to the 5W30, the former has a really outstandingly low NOACK loss (same HTHS, though) and that might be worth something to you if you're just not going to be in cold environments.
I know we sometimes look at pour points when the manufacturers give us no other cold data, but the correlation of it to actual cold performance seems to be pretty terrible. We have CCS results here, so why even mention pour points? Good luck to you if you think that 10W30 is really going to start in your vehicle at -47C...
