10w30 in the summer and 5w30 in the winter WHY

[Garak]

Originally Posted By: FT92
I've run 10-30 winter and 10-40 summer for years , seems to do just fine in anything I've owned

It works, but how is one 10w-XX helping much over another by season?

 

[BobFout]

Originally Posted By: Garak
Originally Posted By: FT92
I've run 10-30 winter and 10-40 summer for years , seems to do just fine in anything I've owned

It works, but how is one 10w-XX helping much over another by season?


Because of the 100c hot visco difference between the two and how it relates to oil temperature vs. climate.

 

[Garak]

For the 30 versus 40 side, sure, but a 10w-30 and a 10w-40 pass the same SAE J300 cold cranking tests. Now, an ILSAC 10w-30 will probably have better CCS and MRV values than a non-ILSAC 10w-40, but they are still both 10w-XX and pass the 10w-XX tests. If I were worried about cold weather numbers, there are other ways to skin a cat. The 5w-30 I'm running now has an HTHS of 3.5 or higher, and passes all the requirements for a 5w-XX. I have no concerns whatsoever about it handling the hottest days of the year in the G37, which has high oil temperatures all the time, and it worked perfectly fine all winter for cold starts.

 

[Nyogtha]

Originally Posted By: BrocLuno
Originally Posted By: 1JZ_E46
In general, a 10W will have a thicker base oil with less viscosity index improved (VII) needed to be a 30 weight at temp. This makes them better, in general, in high temp, high shear environments over a 5W.


+1

I ran 5W-30 conventional in the winter and 10W-30 conventional in the summer in my 2001 Ram 1500 360 /5.9L gassser. When I lived in Louisiana I ran 10W-30 conventional year round. Engine was quite strong still when I sold it in 2013.