Manufacturers went from the near universal 10W-30 to 0W-20 engine oil circa 2007 to meet US fuel economy standards.

-- Chuck

 

0W-30 really works in very cold climates. I drive my 2007 Honda Element up to the Sierra every winter. And on those mornings well below freezing (like minus F) --- the engine starts much easier with 0W-30, than with the original 10W-30 I had in it -- when it was new.

 

I know why I went with M1 75/140, and that is the rear end ran hotter in the S than my truck did running 65 mph weighing 80,000 lbs. We got our '06 S back in '10 and that was one of the first things I checked with my infrared heat sensor. I was very surprised at how hot it got on our long drives up in the mountains. Even just running down the freeway at 70 to 80 mph in the valley, it(rear end) got hotter than my other three vehicles by quite a bit.

ROD

 

Thicker engine oil will reduce mpg. How much of a reduction is hard to quantify without tests but in my experience the 5W30 oil nets a few more miles off a tank compared to the 5W40. The 5W40's oil film is more robust than the 5W30 at operating temp providing more protection for the internals. Motul even says that it will improve power and acceleration. By how much? Hard to quantify but again in my experience both my cars feel a little bit stronger with the 5W40 in their engines. Both oil weights cSt's are more than high enough to keep the bearings/engine happy though.

 

Yep, that is what I was trying to say Just to add to the point above, there is no mechanical downside of using SAE140 but there is no gain either. I wonder if it will even get hot enough under normal use to come alive, I will check on best operating temp for SAE140.

Cheers,

Guy

 

I'll be sure to schedule a track day at Death Valley to get my $17.32's worth... (or maybe just Buttonwillow next summer).

I could have contacted an Amsoil dealer and paid more for 75w110 and probably have to wait longer to get it.

RE: M1 75w90, there seems to be debate whether it is too thin for hard driving due to the 75 rating.

 

Same wave length

 

Is this debate still going on? For those people that don't know and are reading this thread, S2KPUDDYDAD is probably the pre-eminent authority on our differential; he's like the god-father of differentials. This is what he has to say.

Also:

 

The 75w part should not make any difference as that is just the cold viscosity, when up to temp it will be running as an SAE90 and the SHC comes in at 15.1cst at 100deg so not the thickest SAE90 out there but no reason why it would be an issue.

Cheers,

Guy

 

I'm still surprised how many guys still don't understand multigrade lubricants. The stuff could be 0W-90 and still be good. Not sure it's possible to engineer this grade and make it affordable though.

Multi-grade oil has only been available commercially for roughly 50 years so it's understandable the information hasn't yet filtered down to some.

-- Chuck