Napa Gold # 1762 ? Most manufacturers have a short & long version of this filter. I suppose it depends on what brand of tractor the Onan was installed in. The shorty will work, just not as easy to install or removeMN99GT said:Just got a '89 4020 with the Onan 20hp motor. We went to change the oil last night, had NAPA look up the oil filter, but it was way too short... Does anyone have a part # for a NAPA oil filter for this motor?