I have begun to use WW TWC-3 2 cycle oil in my 5500 at sligtly more than 1:275. I also add with that Stanadyne performance at the recommended mix. I did the initial mix in northern Utah for the trip home to St. George and treated 80 gals of diesel. I have noticed that the engine is quieter and I have had an improvement in power also an apparent mileage improvement. I have been averageing 8.3 mpg and on this trip mileage checked at 9.4. This summer with no additives used best mileage was 9.9 on the flats of Nebraska and worst was 7.2 from Denver to Richfield Ut. I also run the Edge on level 3 which may contribute to the mileage help as the big MH will stay in OD rather then shift down. I will be checking it much closer this next Jan on a trip to Quartsite AZ as the terrain will be more conducive to a good mileage check. 9.4 may have been a fluke but I hope not. The trip from above SLC to St. George isn't exactly a flat run and with the little red P/U bringing up the rear my GW has been just over 26K.
Denny