On Mon, 20 Feb 2012 20:28:46 -0000, David WE Roberts wrote:

If in doubt, consult your local B&S dealer or lawnmower shop.

Or wander over to the B&S website, check out the engine
identification page(s), look at your engine, get the relevant numbers
and download the manual. I doubt very much that a 10hp engine is a
two stroke.

Two strokes tend to be high reving and lowish power and used when the
angle of operation cannot be guranteed, which messes up the use of a
oil sump for lubrication, like in a chainsaw or brushcutter.

--
Cheers
Dave.