30 weight- Why not just use in high ambient temps?

[Auto-Union]

SAE 30 has about the same visc curve as 15w40 at lower temps.

 

[ToyotaNSaturn]

Since straight-weights don't perform the cold-cranking tests like the multi-vis oils do, we'll never truly see a straight 30w or 40w oil cold-cranking chart.

 

[Merkava_4]

Just keep using the Maxlife 10W-40 for crypes sake; if you want to experiment with different oils, get a different car.

 

[TallPaul]

If you're going SAE 30, consider using Valvoline VR1 Racing SAE 30. It is fully streetable oil, with extra zddp.

 

[JGmazda]

Ok! I need a new car then.....Not! I'll most likely keep running the 10w-40. No need to run a 5w wt. out here...

I also saw Mobil HM in the same grade was rated "SL". TallPaul- How do think it compares in zddp to Maxlife?

 

[TallPaul]

Typical SL is around 1000 ppm zinc, whereas SM more like 750 or 800. SL is good. I wish Maxlife had stayed SL. But Maxlife has 300 ppm moly which may make up for the lower zddp.

 

[G-MAN]

Quote:

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SAE 30 has about the same visc curve as 15w40 at lower temps.

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True...if the VI of the SAE 30 is high enough.

 

[G-MAN]

Quote:

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Since straight-weights don't perform the cold-cranking tests like the multi-vis oils do, we'll never truly see a straight 30w or 40w oil cold-cranking chart.

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SAE 10W and SAE 20W-20 are straight grades that pass the cold cranking specs for those respective viscosities. The real issue is that there are no cold cranking specs for straight 30 or 40, thus nothing to test.