In Reply to: Re: Oil, Conventional or Synthetic posted by Charles Krammin on December 13, 2017 at 21:00:42:
The Honda website is quite clear and unambiguous and in multiple places - synthetics are suitable for use in their engines as long as you follow the guide lines in the engine specific manual - no exceptions listed.
The Honda GC-190 manual is also quite clear:
Use 4-stroke motor oil that meets or exceeds the requirements for API service category SJ or later (or equivalent). Always check the API service label on the oil container to be sure it includes the letters SJ or later (or equivalent). SAE 10W-30 is recommended for general use. Other viscosities shown in the chart may be used when the average temperature in your area is within the indicated range.
The other viscosities shown in the chart are SAE 5W-30, also for year round use, or SAE 30 for use only when temperatures are above 50F. There isn't a synthetic oil sold that does not exceed to the API SJ service category so that is not the problem. I would suggest the cause of this failure lies somewhere else. Like maybe the owner didn't change the oil as often as he said he did....