I do get just under 23 mpg. It is calculated by filling to the bitter edge of the fill neck where another drop of fuel will not go in. My speedometer is spot on with the GPS, so I know I have accurate measurments.
To get this mileage though, I have to keep my speed at 65 mph with the cruise on. I have a needle valve in my cruise control that slow down the response time of the servo so that it is more like a person driving for pedal pressure response. I routinely go from Portland, Oregon to Salmon, Idaho via Spokane, Wash and Missoula, Mont. The distance is 715 miles over some pretty good grades. With a 7,000 lb trailer at 65 mph I get 18. 5.
My interest in the propane is for towing on the long steep grades. If it drops the exhaust temps 75 to 150 degrees and give a little more power on the uphill, I think it would be OK.
I'm just wondering about the long term affect. All things in moderation is the key. I have 121,000+ turns now and still have my original clutch, brakes, turbo, and VP. I have been running a Edge Comp for about 70,000. My mods have all been researched carefully for performance gain or what I call maneuvering power but with reliability / durability and economy being a driving factor.
So propane for me, would seem to offer good benefits if used in moderation. I'm just trying to get as much info as I can to make a good decision.
Thanks for the inputs.