Originally Posted By: Squishy
Then why are VIIs such a big deal with lawnmowers? Both engines are generally spec'd for 50-hour OCIs, and even then most owners just do yearly changes.
Not sure why you're puzzled by this. It isn't that VIIs are any more or less of "a big deal" for snowthrowers, it's that the benefit of multi-weights for dedicated COLD WEATHER OPE outweighs any possible harm. No one should have a hard time understanding that snowthrowers and lawn mowers operate in different typical conditions and climates. The typical starting condition of a lawnmower is probably above 70F - not so for a snowthrower. True SAE30 DINO (which is what most people use if they use SAE30) would be pretty waxy at 0F.
As we've already discussed, you can get multi-weight rated oils that don't have VIIs as well.
Furthermore, some oils containing VIIs are more shear-stable than others. When a manufacturer makes a specification they write it for the lowest common denominator idiot who is going to put the cheapest [censored] they can find in the machine. The cheapest [censored] SAE30 is most likely going to be better for a lawnmower than the cheapest [censored] 5W30 in typical operating conditions and owner maintenance habits.
If you know you've selected a top quality, shear-stable multi-weight oil based on above-average knowledge and experience - knock yourself out and run it.