Car Doctor: Overfilling an engine with oil can cause leak

A: Overfilling an engine with oil can put additional pressure on seals and, over time, can cause an oil leak. If this were my car, I would return to the dealer and have them adjust the oil to the proper level.

Q: I spoke with the service manager at a dealership, and he said that my car requires slightly more than 5 quarts of oil during an oil change. The dealer charged for 6 quarts of oil. I find this to be ridiculous, because I believe the reminder of the oil can be used in other vehicles.

The dealer performed a complete oil change today. I checked the oil level and it is at the correct level. I am leaning toward having my local mechanic perform this service in the future, since the travel to the dealership is one hour each way and the service time is long.

A: In one of my cars, the engine takes 5.8 quarts of oil and you pay for six. Unfortunately, oil is sold by the quart, not the ounce, even when it is dispensed from bulk tanks. You could always ask for the remainder of the sixth quart to have on hand to add to the engine if needed.

Regarding having your car's engine oil changed locally, as long as it is the proper grade of oil and they use a quality filter, I see no problem with it.

Q: I have a 2015 Volkswagen and went to change the oil. After removing the pan that covers the engine (a pain in itself), I found the engine oil drain plug and it used an odd tool to remove it. I was going to use vise grips on the plug, but I was afraid I would damage it and not be able to reinstall it. I gave up and put this entire project off for another time. Any thoughts?

A: Volkswagen and Audi use a variety of drain plugs; some are plastic while others are a 16 millimeter triple square (Torx style) driver. If you are going to continue to perform oil changes, you have two choices: you can buy the tool or replace the oil drain plug with one that uses more common tools.

Dorman auto parts makes a factory-style replacement that uses a more common Allen wrench that may be easier to find.

Q: I love my 2009 Toyota Camry Hybrid. It runs well and — when I baby it — can get 41 to 43 miles per gallon. Is there any way to recalibrate it (Toyota or aftermarket) to produce better performance? Adjusting the computer and something else?

A: Any tuning changes would, in my opinion, have a minimal if any effect on horsepower or performance.

There are some products that claim "up to" a 30-horsepower gain, but I wouldn't spend the $200 to try it.

Even minor modification — such as changing the air intake and exhaust — would have a minimal benefit and just add noise to an otherwise very quiet car.

In a conventional Camry, horsepower is gained with turbo or supercharging, and in addition to the expense ($2,000?), hybrids are really made for this. I think I would just enjoy the mpg.

Q: I have a Mercedes-Benz C350 with the "check engine" light on. Should I take it to the dealer or can the place I buy tires repair the problem?

A: The "check engine" light can come on for any number of reasons; a sensor reading outside of its limits, poor engine performance, faulty catalytic converters or even a loose gas cap.

At this point, any shop should be able to scan the computer, read the code and give you some direction on what to do.

John Paul is the AAA Northeast Car Doctor. He has more than 40 years of experience in the automobile industry and is an ASE-Certified Master Technician. Write to John Paul, The Car Doctor, at 110 Royal Little Drive, Providence, RI 02904. Or email [email protected] and put “Car Doctor” in the subject field. Follow him on Twitter @johnfpaul or on Facebook.