Really? No commercial operators use Stihl's 4-mix products, which is a 4-stroke engine sans the oil sump, or any of the Dolmar 4-strokes? Posts in this forum would seem to say the opposite for, at least, the former.
Scag Tiger Cat 48-inch deck, Kawasaki motor
Lawnboy 10227 2T push mower
Stihl BG86 handheld blower
Stihl BR550 backpack blower
Stihl KM110R kombi system with lots of attachments
Stihl HS45 hedge trimmer 24-inch blades
Echo SRM210 trimmer