The welding machine on my work truck has an Onan gas engine: Model # P216G - I/11519H Serial # J987814561 No complaints with starting/reliability/power etc BUT starting to hate the oil cap! It's designed to slide on, turn & lock into place with 2 tabs on the oil dipstick tube. Even new, it wasn't a tight fit - presumably to allow crankcase venting. This was in contrast to an older welding machine we have with (I believe - will check) the same engine - it's cap threads into place securely. The old machine still has the cap/dipstick it was delivered with about 6+ years ago. The machines with the newer style cap (we have 3 of them) seem to start out with breaking the dipstick off where they attach to the cap. (Thin metal, 90 degree bend, about 1/32" of material on either side of the hole) Replace cap, few months later same thing . I think this may be due to the fact that this style of cap vibrates more than the older setup. Gave up on leaving the dipstick attached to the cap - use the new cap with stick to check the oil and the old cap WITHOUT stick while running. Eventually, the plastic cap wears to the point that the tabs don't hold it securely and it can (has) popped off while running . Mounts for engine-to-welder and welder-to-truck appear to be OK and all 3 of our newer machines have done this, I'm wondering if A} anyone else has run into this problem and B} if there is a fix - other than replacement of oil cap every month or so! I wonder if the older style tube/cap can be retrofitted?