When to Change Your Engine Oil, and What 0W-30 Means

There is no single number for every car. The oil change interval is set by the maker in the owner's manual, by distance or time, whichever comes first, and many modern engines work it out themselves and show a message on the dash. But the manual usually separates normal use from severe use, and most driving in our cities is the second kind: high heat, traffic that keeps the engine running without covering distance, short trips on which the oil never fully warms up, and dust. In that case, follow the severe-use schedule. The two numbers on the can, such as 0W-30, describe viscosity. The first, with the W, describes how the oil behaves at a cold start: the lower it is, the faster the oil reaches the engine's parts in the first seconds. The second describes its thickness at running temperature. The right oil is the one your manual asks for, not the thickest and not the cheapest. Remember three things at every change: change the oil filter with it, check the level on the dipstick a few minutes after switching off, and keep the service invoice in the car's record; it holds its value when you sell. Between changes, check the level every two weeks. Oil that drops quickly or turns milky is a reason to see a technician.