Synthetics are not needed by most of us, and in reallity, probably not by any of our tractors. Use a name brand conventional oil,(Shell Rotella, Mobil Delvac, Chevron Delo) and adhere to your prescribed maintenance schedule, and your tractor engine will likely outlive you. Many truck engines go over a million miles before an overhaul is needed, using nothing but a conventional 15w/40. Personally, I've put 700,000 miles on a Cummins before selling it....don't know how much longer she went...but it wasn't using oil, smoking, or making strange noises, when traded in. Now..700,000 miles is at least 17,500 hours....my tractor gets about 100 to 120 hours use a year....so it should last another 145 to 175 years on conventional oil.....that will make me more than 211 years old......I'd better go find some really good vitamins.....Hill Billy Bob