Q: I learned that my mechanic has been filling my 2008 Chevy Impala with 5 quarts of oil, instead of the recommended 4. I've also noticed an oil leak, which my mechanic attributes to a bad manifold gasket or head gasket. Could overfilling the oil have caused these gaskets to leak? It's a 3.9-liter six-cylinder engine with 104,000 miles on it.
A: No. It sure would be nice to blame this guy, wouldn't it? But overfilling the crankcase by a quart is not likely to cause any problem. The mechanic should have checked both the oil capacity and the dipstick. But he may have assumed that a large six-cylinder engine like yours would hold more than 4 quarts. Most of them do.
Your oil leak was caused by those 104,000 miles on the car. And it could be a big job to fix. If you need to do both cylinder heads, you could be looking at well over $1,000. Even if it's just the manifold gasket, it could cost several hundred bucks.
So, unless it's leaking a lot of oil, you may want to apply the technique of "watchful waiting." That's the program my wife has me on. It involves three steps: Keeping a close eye on the oil level, topping it up whenever it's low and putting a piece of cardboard on your garage floor before it looks like the Exxon Valdez has been dry-docked in there.
If you're losing less than a quart every 800 miles or so, this leak is of little consequence. It's possible that something worse will lead you to replace this car before the leak ever has a chance to become a mechanical threat.
Don't slip
Q: Is it good to keep the traction control switch off in summer driving?
A: Traction control detects if one wheel is spinning faster than the others. If it is, the system concludes that the wheel has lost traction, which can also lead to loss of control of the vehicle. So, it uses the ABS break system to slow down that wheel until it regains traction.
While snow or ice are the most common reasons for a wheel to spin, they're not the only ones. Rain, leaked oil, or a patch of loose dirt or sand can cause a wheel to lose traction. And when that happens, you want your traction control to work.
Plus, there's absolutely no downside to leaving it on. You're not wearing anything out. It's inactive until it gets a signal that a wheel is spinning. Turning it off in the summer would be like turning off your home's fire alarm when it's raining. Sure, you could. But why would you?
Contact Ray Magliozzi via e-mail by visiting cartalk.com.
