Low hours though. My 25 Kohler was switched over at the first change to Mobil 1 10-30. It now has just under 700 hours. My Kubota gas on the Grasshopper is at about 2800 hours and has had Amsoil Diesel 30 until the last two or three changes. It now has Mobil 1.
I use mobil 1 also and the two engines have around 1300 hours. Never have had any temp. related problems. My truck also runs mobil1 and i use high octane gas always. The high octane and synthetic oil compbination will make an engine last longer in my opinion. My truck sounds great and people cant believe how great it sounds after seeing what it looks like. The sythetic tranny fluid did not save my transmission though.
I don't use synthetic oil, but I do use an additive called Tufoil, http://www.tufoil.com if you want to check it out. I've used it for the past 12 years and had great luck with it. It is in the Guiness Book of Records. It is so slick that an easy turning filter becomes a big chore to turn off if some oil starts running down the side of the filter when taking them off. You can't grip it hard enough to turn if off with your bare hand, so I have to use a rag at this point. It makes the engines run cooler, which is a good thing on air cooled engines. I didn't know how much cooler until I put it in the new diesel Chopper I got in June. After 150 hours I put it in the diesel, which was during a very hot spell we were having. The diesel has a temperature guage on it and it ran 10 degrees cooler after putting the Tufoil in it. BTW, a water cooled engine doesn't run that hot to start with, so an air cooled engine could run much cooler.
I have run Tufoil in the 3 Kohler engines I've had plus all other 4 cycle engines and diesel engines, including the trucks and personal vehicles for the past 12 years. The 3 Kohler Engines, (1) 20 HP Magnum traded it in at 2000 hours, (2) 20 HP Magnum, sold it to a friend and it has over 2,500 hours and still runs good, (3) Still use this one, 22 HP Command with 3,235 hours and it still runs strong.
This additive is $125 for a gallon which treats all my engines for close to 2 years. You need 8 oz for a V8 engine the first time and 4 oz each change after that. An 8 oz bottle is around $11.00, I'm just trying to answer future questions here before I get them.
I appreciate the info Eric. The reason I asked for info on synthetics is I am trying to find out how long an air cooled engine would last on synthetics. There will be 2 more followup threads on normal oil and oil with additives.
I bought a used Walker in June 00 and since then have run Mobil 1 10w30w and the engine seems to run cooler. I also change over all the other fluids to Mobil 1. Gear boxes and hydro's seem to be running cooler also. Time will tell how long things will last. To me air cooled running cooler will last longer. So yes I think Mobil 1 will help in longer life in your engine. Cost a little more, but if it last longer you are money ahead.