Used to work with a lady that got taken coming and going by a dealership. won't mention the brand but by 48k mile the car had been given 6 sets of plugs and wires, 2500 for brakes all round and was burning a quart of oil every about 40 miles. I told her to get the service history and the amount of junk stuff she'd been charged was criminal. Had her get on the phone with them, since the car was back in, and told her to request a compression check since my suspicion for the constantly fouling plugs and the oil use was a bad cylinder or cylinders. They actually laughed as I listened in and said that was obsolete diagnosis and besides, couldn't be done without replacing the plugs and wires, again. Had her go get the car and said find another place to fix it. Another dealer found that the engine was bad, probably from new, with 2 cylinders out of 4 showing minimual compression. At least the manufacturer paid part of the replacement cost, but she'd paid round 5k for work in the 3 years she'd had the car.