This being my first diesel engine, I have some concerns over oil changes... frequency, grade of oil, additives. How different are the diesels to their gas counter parts? Should I change the oil more frequently? Less frequently? Synthetic? Blend? Additives like Marvels? What about an occassional gas additive to "clean things out"? The closest biodiesel reseller is 3 hours away, so I can't use that although I'd really like to.