What motor oil should I use?

This question was posed on the club's Discussion board in the Clubhouse.  Read the response from Al Eden, a long-time Simplicity dealer (see more info).  I've posted it here for easy access.

Subject: RE: What oil for B-10
Posted: 1/5/2001 9:10:12 PM

Hi,

Both Briggs and Kohler call out SAE 30 for Summer and accept multi-grade for Winter. Kohler also has a CAUTION with their recommendation. They say that excessive oil consumption and excessive carbon build up may result when you have the multigrade in. In service schools for both manufacturers both are adamant that Multi-grade is not "tough" enough to stand up to the aid cooled demands.

The exception is the Kohler Commands and the TH engines they call out 10W-30 for Summer. First they have hydraulic lifters [350 Chev] and have addressed the cooling problems that cause oil breakdown in the L head engines. When I first became a dealer about 20 years ago, I bought a 7117 and used it for a demo. Oil just ran through it, I called Kohler and they asked me if I read the manual [No] then they explained to me about oil and heat. I read the manual and changed the oil to 30 and consumption stopped.

The problem is with the L head design. The cylinder in the area around the exhaust valve is extremely hot compared to the rest of the cylinder. Multi-grade breaks down in this area. Multigrade can not handle these temperatures, and 10w-40 is not as tough as 10w-30 to my surprise.

In the new Commands and TH the overhead valve design moves this heat from the cylinder wall up to the cylinder head. This allows the cylinder to cool more uniformly. The operating oil temperatures in these engines are much lower than the L heads. This is why almost all of the L head engines will be gone after this year. With all of these temp variations they can't meet the ever tightening emissions standards. This has been one of the biggest benefits of the TH engine. The fact that there is no head gasket reduces the temperature variations from the top of the cylinder and the head. Lower and more controlled emissions, this temp break at the cylinder head has been a problem with emissions. Much has been done with moving the ring up in the piston, ring thickness, etc. because this little area along the side of the piston above the rings at the top of the cylinder that is out of the flame front doesn't burn the fuel properly. Controlling the temperatures helps and also allows multi-grade oil to survive in air cooled engine.

Sorry -- you ask for the time and I tried to tell you how to build a watch. 

Good Luck,

Al