So I’ve tried 3 grades so far: 5w30, 10w30, and now been using 10w40. I have worn oil rings or whatever and I get blue smoke after idling long, especially in hot weather. Changing the grades of oil hasn’t made a difference with this.

However, 5w30 would burn thru quickly...and leaks.
10w30 fairs a little better.
But recently I switched to 10w40 and noticed far less oil leaks (despite me already doing several oil leak fixes).

I’m just concerned about gas mileage, because I drive a lot on highway. I already don’t get the best gas mileage, but wondering if it’s even noticeable. I’m also considering 0w40 for quick flow at startup, but heavy enough to not leak at highway temps.

I've not heard of the VH41DE 'wearing out' in the rings and valve guides? I suppose it's possible. what specifically is leaking (much more common)?
as to oil grades, I'm a huge fan of full synth 0w oils. I ran straight M1 0w-30 AFE in the VH41.
I run 5qt 0w-30 AFE and 1qt 0w-40 in the VH45DEs. Have stuck with this blend now for many many years, and I have phenomenal UOAs to back it up.

Smoke at a traffic light indicates worn valve seals,not harmful but based on price most people ignore.

No oil recommendations.