>> But that doesn't explain why 10-30W is not good for it. Although the hp
>> output of the mower may exceed that of my van....... :-)

>HP isn't the criterion, its the internal design of the bearing, engine
>lube pressure,

I was joking :(

>10-30W could be far too low viscosity under cold conditions.

I seldom mow my lawn when it is snowing <g>

>Think of the origins of the classification system - a large body of
>knowledge about straight oils and little if
>any about multi-weight oils.

Are you inferring that no one knows anything about multiweight oil?

>Another tip is to trust that design engineers know a little bit more
>about what they've designed than they are usually
>given credit for, especially when it comes to Vanagons!

I am a design engineer, and I wouldn't trust anyone blindly about
anything....

So I should blindly trust one engineer who makes a great car, and ignore
the ones who make the oil?

Still no answers on why anyone should use straight weight over multigrade?

At higher temps, is 20-50W the same viscosity as just 50W?

Thanks,

John