[dremd]

I certainly do not know about economy; but once upon a time we poured out 10w30 dino oil from a 7mgte, poured in 0wt 10 and consistently gained 10 whp.
The Motor in question had about 150k on it with original seals, it didn't leak until the pcv plugged up and blew every seal out of the motor around 200k.

Leaking is a hard thing to call; but I can't think of a reason that the leak wouldn't shrink back to its invisible state (which will eventually grow and get blamed on your thin oil experiment) if you switch back to the thicker oil.