I can attest to what sigma is saying. In highschool I worked in the lube bay of a car dealer and we serviced tons of cars on a daily basis.
I knew some of the kids that worked there did not change the oil on vehicles they serviced. They would change the oil filter, but not the oil.
However some of the idiots that worked there didn't even do that and were eventually caught when the customer came in pissed still having a Jiffy Lube oil filter on their vehicle.
