I've been using Mobil1 10W-30 'Hi-Mileage' but was thinking of using motorcycle oil. I couldn't find any right off hand, but I did find Valvoline Racing Oil in 10W-30. I used that in my 22 year-old Lawn Boy Insight (10684 with Tecumseh LEV-195). I noticed smoother running right away but after fully warming up, I thought it had picked up about 500 RPM. I haven't checked that yet but if true, it indicates a big reduction in friction.