Getting the generator ready for hurricane season. its a Blackmaxx 8,000 kw with a Honda GX390 13 hp. runs excellent, very reliable, and we have it converted to run off of natural gas. Whatwould be the best oil to run in this engine? I think it specs 10W30, i would go with either Rotella T or T5 10W30, or Mobil 1 Turbo Diesel Truck 5W40, or would the 5W40 be too thick? it only holds about a quart. I think with the natural gas hookup it burns much cleaner and the oil stays cleaner. so would the 10W30 be better than the 5W40?