The manual on my 2001 Honda Harmony lawn mower with a OHC engine recommends synthetic 10W30. I ran Mobil 1 10W30 for years with zero issues, but for the last couple of changes I've run Pennzoil Ultra 5W30 because that's what I'm running in my autos. Even though I live in the SE US (100 degree ambient temps in the middle of the summer) and mow about 3/4 of an acre weekly for about 9 months out of the year I really am not concerned about shearing down as this highly refined Group III oil has excellent viscosity properties and should require minimal VIIs. I'm putting about 72 hours on the engine per year and changing the oil at the end of each mowing season. So far no problems and the oil looks very good (only slightly darkened from new) when I do the oil change. I have taken the motor apart for inspection once and it looked great. I can still see the factory hone marks in the cylinder walls. If I were you, I'd run the factory recommended 10W30 synthetic with no worries at all and do yearly oil changes. I like to change my oil at the end of the season so that any reactive combustion byproducts don't sit in the crankcase over the winter season.
The mower runs like new. It pulls with one start and seems to make as much power as it did when I bought it. I would recommend staying away from E85 (Gasohol) fuel if ethanol free fuel is available in your area (had a fuel gumming issue with it in all my OPE engines after sitting for the winter even *after* running the fuel out of the tank). These are really great engines and if taken care of will outlast the mower deck and drive train (in fact, I'm about to have to put new rear wheels on my mower as the tread is completely gone.
The mower runs like new. It pulls with one start and seems to make as much power as it did when I bought it. I would recommend staying away from E85 (Gasohol) fuel if ethanol free fuel is available in your area (had a fuel gumming issue with it in all my OPE engines after sitting for the winter even *after* running the fuel out of the tank). These are really great engines and if taken care of will outlast the mower deck and drive train (in fact, I'm about to have to put new rear wheels on my mower as the tread is completely gone.
