[PinkoDiesel]

Mine said B20 is the highest that GM recommends and will support with the warranty.

I have ran B99 in mine for over 4000 miles and had no trouble at all. In fact it runs much cleaner.

I do notice with a B50 I have the best power, throttle response, and fuel economy. When running the B99 my MPG is 20 and with B50 - 22mpg and full diesel - 25mpg.

But the Bio causes no soot build up in the engine in fact it breaks it down and shoots it out the exhaust (just hot air no diesel smell - french fries). Just beware that if you're planning on running any Bio above B20 you need to have a water seperator system with better filters than the stock one.