How often do you rev your engine high (4000+rpm)?

What would possess you NOT to use the weight Toyota recommends?

 

Meow?

 

I remember 5w40 being an option for people dealing with oil loss between changes (helped in some cases). Why one formulated for diesels puzzles me.

 

How long have you owned these cars?

 

I had the Gen 2 from 4k miles to 202k miles. It still was quiet and low on oil use. I'd still have it if it hadn't gotten hit. I just got a gen 3 and plan to peg the throttle wide open the same way. I routinely run this car at 116mph for hours on end when not towing. When I start pulling the trailer (next weekend) the oil will get even hotter. I find that when I hold the throttle open it uses oil. I put in a new PCV valve and I'll monitor oil use. I live in Florida and 0w-40 goes from 75cSt to 13.5cSt. from 37Cot 100C. I'm pretty sure my oil goes higher than 100C. 0W-20 goes from 45cSt to 9cSt. If I run that hot then that 9 is probably going to be 7 at best. My top ring and bearings are gonna get beat. Diesel oils have lots of zddp. That's a good protector. Any else here on the same page with me?

 

Not me, I am not more of a chemist than Toyota's experts.

 

Why do Mercedes-Benz's experts recommend (if I understand correctly) 0W-40? It's not clear whether that differs so radically from from Toyota's 0W-20 recommendation more because of actual physical differences between cars of those two brands, or merely because of differences in marketing and political philosophies.

 

The higher number is for dealing with heat and the smaller number is for dealing with cold. Perhaps MB motors run hotter on average?

 

Probably that Mercedes engine just has thicker clearances between moving parts. Larger clearances need thicker oil to fill the cap and keep the oil pressure up.

You can also just use bigger oil pump to compensate for higher clearances. And oil temperature (engine temperature, and outside temperature) also effect in oil choose since oil viscosity is effected by oil temperature.

 

Toyota doesn't agree with themselves: their Australian Owner's Manual recommend a more old-school gamut of oils. From the 2010 book:



(the top grade, partially obscured, is 0W20)

 

I wouldn’t say that is a recommendation to use thicker oil grades. It just tells that it’s ok. I would not use anything thicker than xxW-30 even in 38c/100F temperatures since they say that even using xW-20 would be fine.

 

I ain't buying the theories that M-B engines run a lot hotter under the same conditions, or that M-B's capability to machine engine parts to tight tolerances is greatly inferior to Toyota's. My guess, which I'm sticking to until proven wrong, is that the Germans (including BMW too?) are more concerned about avoiding engine wear under extreme (as in autobahn) conditions, and less concerned about squeezing out the best possible mpg in USEPA testing.

Mendel, thanks for the Australian recommendations. I'd wondered about that. I might try 5W-30 post-warranty. I rarely need to start the car at temperatures under 30°F, and very rarely under 20°.