Mower, 1992 Lawn-Boy S21ZSR To date, always used Lawn Boy oil @ 32:1 First, the back story: The lower seal started leaking again, and oil was sprayed across the deck. 3rd seal in the last 5 years. 1st time I just replaced the seal. 2nd time I checked the crankshaft (even though I never hit anything hard) replaced upper & lower bearings, + the seal. This time, I asked the repair counterman at the lawn, garden & feed supply store what gives? He asked if the muffler was heavy with carbon. It was. The repair counterman said that the mufflers could get clogged and cause back pressure. Suggest I de-carbonize or replace the muffler & seal. GET THIS! He also claims that the 32:1 mix is too rich. That Lawn-Boy was being far too conservative on their lubrication standard. He sez that you can run a modern 2-cycle oil in the Lawn-Boys at 40:1 and still provide sufficient lubrication, while keeping the carbon buildup down. Question: What say you all? My 2-cycle trimmer, blower and chain saw all call out 40:1 With the new lubricants - may of which are synthetic, - can the ratio be pushed up for this 1992 Lawn Boy as well? Thanks!