I understand that for well-made gas engines, idling doesn't damage anything. I also understand that diesel engines can suffer from wet stacking when run under light load for long periods.

The extended idling is bad comes from the carburetor days from what I can tell.

Odd that diesel has an issue since you always see them idling. Though the newer ones with DEF there are some issues.

Blast,

We need to come up with the engineering to pull kilowatts off of our Tacomas!

I have been told it is not the engine that is the problem, but the transmission. I was told to put it in drive periodically to insure complete lubrication. True or another falsehood?

For modern vehicles, I'm thinking this is correct but "periodically" is closer to every month than every day.