I tried 10w40 in the Aerostar which consumes a quart every 1300 miles and it didn't seem to help, though I did not give it a long try, not even an OCI. Might help. Thicker should reduce it some.
I think maybe better is straight weight, SAE 30 or SAE 40 (which you could easily do in OK summers).
Do you get blue smoke from the tailpipe? How much consumption?
I finally decided to just live with the Aerostar's consumption. One thing nice about it is that you get to play with oil every 500 to 1000 miles to top up. Not all that bad a deal, and since you are adding so much fresh oil, you can extend the OCI some. I am limited to about 5000 miles with the Aerostar, though, because that is one year.