Oil Should Be Kept at Full Level
Question: After having had an oil change and letting my car sit overnight, I checked the oil stick in the morning, and it showed that the oil line was about three-fourths of an inch above the full line on the stick. I took the car back to the garage that changed the oil, but the mechanics ignored my complaint, claiming that it was so minor it would not hurt my car. I would greatly appreciate knowing whether these mechanics are right. --W. B. K.
Answer: The amount of excessive oil probably will not damage your engine, but it is undesirable. It is impossible to know how much extra oil your engine can tolerate before it is damaged--so why experiment? Even if the extra oil does not damage the engine, you will have trouble keeping track of your oil consumption. And finally, the practice of overfilling is just a sloppy habit.
Far too often, engines are either overfilled or underfilled by up to one quart. The reason is that mechanics are too lazy to check the dip stick and adjust the amount of oil they add.
Rather, they pull a chart or manual that shows a certain engine takes four quarts. In fact, many newer four-cylinder engines are supposed to take four quarts, according to the owner’s manual, but require only 3 1/2 quarts to reach the dip stick’s full line.
The dip stick is the sole determinant of the correct oil level for the engine. Despite what the owner’s manual says, you have no choice but to trust the dip stick, according to engineers at auto manufacturers. The reason is simple: If the dip stick is wrong when you change the oil, then you will never know whether to add oil between changes.
The oil pump draws oil up from the bottom of the engine’s oil pan, where it settles. If the pan is so overfilled that the crankshaft dips into the oil, you have a serious problem.
The crankshaft would churn the oil and create pressures inside the crankcase that could pop the engine oil pan gasket or the crankshaft end seal, according to Bill Runkle, an oil expert at Valvoline.
If the engine is left underfilled, you have another set of problems. Many new engines use only three to four quarts of oil, compared to the five quarts that was more common years ago. If you drive out of the garage a half quart or a full quart low, the oil is going to operate at a higher temperature and get dirty quicker. You are closer to the threshold of the engine and don’t have adequate oil to maintain the proper pressure in the system.
A mechanic following correct procedure would put three quarts of oil in an engine, start the car to fill the new oil filter and then shut it off. Then he would add oil until the level registers full on the dip stick.
At the garage, you can avoid this problem telling the mechanic that the car takes less than four or five full quarts. Say in explicit terms that you do not want the engine overfilled.
Vartabedian cannot answer mail personally but will attempt to respond in this column to automotive questions of general interest. Do not telephone. Write to Your Wheels, Times Mirror Square, Los Angeles, CA. 90053.
