Q: Normal to have to add oil before next change

If your car is not leaking the oil, most likely the car is burning the oil. This can mean a couple of different things.

A PCV Valve (Positive Crankcase Ventilation) that is not functioning correctly will cause the engine to burn excess oil. This valve is designed to draw excess fumes from the crankcase which also creates a slight vacuum. The correct flow of the PCV valve also helps to regulate engine vacuum. When too much pressure or vacuum is present in an engine, this can cause the oil to be pushed to the top of the motor through the cylinders and past the piston rings (piston rings are designed to prevent oil seeping beyond them) and into the combustion chamber causing it to be burnt along with the air/fuel mixture. As the fuel ignites, the oil does as well causing it to be expelled as exhaust. A new PCV Valve is commonly an inexpensive fix to this problem and can prevent very expensive oil leak problems if caught early.

General Motors indicates that oil consumption of about 1 quart per 2,000 miles is normal. As the mileage of the car increases mechanical parts and seals will slowly show wear which will contribute to this as well. The next time you have your oil changed, have the mechanic check for oil leaks and inspect the system to make sure everything is working well.