I know this doesn't answer your question, but I have steel 19.5's on my dually. They are HEAVY. Maybe aluminum would be better, but I don't think your mileage will go up much. They do last a long time which is good, cause they cost almost double what 16's cost..
Well after running beautifully for me for almost a year, she quit running suddenly like it ran out of fuel. I ran and got 10 gallons and poured it in. No dice. Cracked an inj line, no fuel on cranking. I've been meaning to put a new lift pump in it for piece of mind, so i did. No dice. I think...