for my first diy tranny fluid change since I bought my 05 Road King last year, I bought Lucas 85/140. I did alot of reading since its my first time, many others were mentioned. Other recommendations I came across were Mobil 1 75/90 or 75/140. These were my only choices at the store I was at anyways, so I got the thicker one. I havent done the fluid change yet, and decided to check the lucas website to compare the one I got to anything else they may have. The one I bought is the "Heavy Duty Gear Oil" 85w-140 and it has a picture of a 18wheeler on the front, it doesnt say synthetic. But their website has a synthetic gear oil 75w-140, which would be better?