I am considering switching to a sythetic diesel oil (Rotella 5-40) due to the added detergents/additives and wide operating temp range. My 86T has responded well to car based synthetics so far. Internet searches have yielded decent results, but as always with the internet, conflicitng opinions arose. What do you guys think? Any personal experience? FYI: emissions are not an issue, O2 sensor will be bypassed in near future for other reasons.