I run either stanadyne performance formula(winter) or power service diesel kleen(summer) all year round, in every tank in my '99 E300 and '02 TDI. Recently I've been running 100% biodiesel in the TDI, and have been running 20 percent blends(B20) in my E300 for a year. It really runs much quieter and smoother on B20. I still dose the fuel on the E300 with additives relative to the amount of gallons of petro diesel I put in... Good luck, and use the additives and premium diesel fuel whenever you can.

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2004 Ram 2500 Cummins HO
2000 Jetta TDI
1999 E300 (sold)