Determining oil change intervals

Question:

The oil change interval on my 1960s cars has been in the 2000-mile range. And over a period of 40 years, engine overhauls have shown the merits of this maintenance practice. Each and every engine had only the slightest amount of heavy oil buildup anywhere.

Since I am older and don’t drive the cars as much, a 2000-mile interval can last two years. In the winter months each car is driven a few miles every few weeks for exercise.

Are harmful chemicals building up in the oil over time? Or is 2000 miles still 2000 miles?

Should I change the oil every year or is the difference negligible?

Answer:

In general, the oil’s effectiveness in protecting your engine from wear and damage degrades as a result of both use and time. There are, however, a great many variables that influence the rate and extent of deterioration so it is not possible to formulate an oil change interval rule that is optimal for all vehicles.

For example, short trips can accelerate the demise of your oil’s effectiveness so when you exercise your car in the winter make sure the engine reaches full operating temperature and remains there for at least 20 minutes.

To determine whether your oil needs to be changed after a particular time or mileage interval, send a sample to a lab

for analysis. If you don’t want to be bothered with that, then adhere to a change schedule that is frequent enough to give you peace of mind but not so frequent that it wastes money and squanders our precious natural resources.