I always get curious, when I hear of NonSynthetic 20w50 being used in

a Vanagon H2OBoxer Eng, as to what prompts the user to do that ~ 

> On 7 Aug , 2022, at 9:41 AM, Dan N <dn92610@GMAIL.COM> wrote:
> 
> thank you Dennis,
> 
> I wonder if there's something to do with the oil grade they recommend with
> the RPM of the engines... On my ML430 suv it's about 2K rpm at 70mph... On
> the vanagon it's 4K at 70mph. At 55mph it's about under 2K rpm for the suv
> and about 3K rpm for the vanagon. The suv uses 5W40 synthetic, I use
> non-synthetic 20W50 on the vanagon.
> 
> On Sun, Aug 7, 2022 at 7:37 AM Dennis Haynes <d23haynes57@hotmail.com>
> wrote:
> 
>> Recently there was some discussion on engine oil. So I'll add more
>> thoughts to the discussion.
>> Recently I acquired a 2022 GMC Sierra Crew Cab, Denali. Has the 6.2L and
>> 10 speed Allison. Will soon be having its 1st oil change done. Part of GM's
>> plan to improve fuel economy is the use of low viscosity lubricants. The
>> engine calls for 0w-20, the transmission use special low viscosity ATF, and
>> even the axles call for 75w-80. I having a hard time wrapping my head
>> around using the 0w-20 oil for an engine of this horsepower. To add to the
>> confusion the hopped version of this engine for the Corvette calls for
>> different oil.
>> 
>> So doing some research I learned something that I never gave thought to.
>> Engine oils contribution to an engine going into pre-ignition. Makes sense
>> given some thought. There is always some oil on the cylinder walls and some
>> part becomes part of the combustion process. For the Waterboxer this is
>> relevant as there is also some oil laying in the bottom of the cylinder.
>> For my engine it has active fuel management, (AFM). Glorified cylinder
>> deactivation. Under certain load and speed conditions the cylinders get
>> deactivated via a dance of turning off the injectors, and de-activating the
>> valves. In this state oil that gets past the rings isn't burning off.
>> 
>> GM addresses this as part of their Dexos specifications. The oils
>> contribution to detonation is also of concern for engines that are direct
>> injected and turbo charged.
>> So to add to the confusion there is Dexos 1, generation 1, 2, and now 3,
>> and Dexos 2. Now one would think that Dexos 2 would be the later or
>> improved spec. It is not. Dexos 2 is for europeant vehicles which addresses
>> that many European vehicles are Diesels. The performance for spark ignition
>> engines is actually lower.  The GM specs also include other ratings that
>> also include fuel economy. Oils that carry the Dexos 1, generation 2 or 3
>> rating is limited.
>> 
>> How does this apply to us? There are a number of folks that think heavy
>> duty Diesel oils are a better choice for the Waterboxer. The pre-ignition,
>> detonation control is just another consideration for using oils that are
>> designed for gasoline, not diesel engines. Pre-ignition is the cause of
>> most melted pistons and a contributor to rod bearing failures. For the
>> Vanagon it is of significant concerns as due to all the other noise and
>> design of the engine it is not easily heard when it occurs.
>> 
>> Dennis
>>