I use Mobil 5W40 with Donaldson or Wix X filters. Change oil when minder goes off, usually around 10,000 miles. No problems. Any synthetic will give better protection than standard oil. I'll let you know how the oil sample comes back. I use synthetic in everything I own (vehicles, skid steer, garden tractor, lawn mowers, tiller etc). Never had an oil related failure using synthetic and it holds up better especially on air cooled engines. As long as it meets the manufacturer's specs, you should be good. More important than brand that it meets the manufacturer's specs.