Without wanting to defend the engineers corner too much, it's a waste of time as one can see by these recurring threads anyway...
Look through the 50hr Check in the LAMS schedule and there is actually more to it than change the oil/filter and 'kick the tyres'.
Remember there is paperwork to be raised before the job, during the job and after the job. The majority of our customers use tech logs or journey logs which rarely tally by the time we transfer the figures into the aircraft log books. Most owners present their aircraft in a pretty filthy state and they can't be inspected through the dirt so they have to be cleaned.
Cowlings have to be removed and the whole engine installation inspected for possible defects as well as the oil/filter/plugs/air filter change/inspect as well as the whole airframe. The oil filter is cut open and inspected (how many car garages do that?). Spats have to be removed and refitted for the job to be done properly.
If you had a £20-40k value car you would be paying up to 2 or 3 times the £38/hr labour we charge. We work on 8 hours labour for something like a PA28-161 for a 50 hour check. If people really think that the job can be done quicker than good luck, I'd love to come and watch you do it!
As for things being found defective, the majority of the GA fleet being some 25+ years old and flown the equivalent of half a million miles - what would cars be like at that age/mileage.
I don't dispute that there are some rogue traders out there as there are in all walks of life but please don't tar us all with the same brush!
If you are doing your own maintenance then good luck, I'm sure you are doing it in a sensible, clean environment and with all the right tools and manuals to hand (as legally required by the CAA LAMS).