I have a question for you engine gurus. I own a Genrac standby generator that is powered by a one cylinder, natural gas fueled engine. I just changed the oil and filter and was shocked when charged $10 for the new oil filter. I have been searching for a Fram or STP replacement filter but haven't been able to locate a list where I can cross reference the Genrac part number to a replacement part number. I was told by one mechanic that if the threads of the replacement filter should fit the generator's engine, it would be OK to use the filter. That seems like a stretch to me. Would a replacement filter that is physically the same size as my Genrac filter be OK to use? Thank you in advance.