Why check it yourself
Between oil changes, an engine can burn or leak a small amount of oil. How much varies widely with the engine’s age, design and driving style. Running low can cause serious damage quickly, whereas a regular check takes only a few minutes. A reasonable habit is to check about once a month, before a long trip and whenever you are refueling and have a minute. Older or high-mileage engines often deserve more frequent checks.
Some modern cars have no dipstick and instead show the oil level on the dashboard display. In that case follow the manual’s procedure. The rest of this article assumes a conventional dipstick.
What you need
- A clean paper towel or lint-free rag.
- A level surface.
- Your owner’s manual, if you are unsure where the dipstick is.
Step by step
- Park on level ground. On a slope, the oil pools unevenly and the reading will be wrong.
- Wait if the engine is warm. Oil needs time to drain back into the pan. Many manuals suggest waiting a few minutes after switching off a warm engine, while some specify checking cold, before the first start of the day. Follow your manual. Be careful, since engine parts can be hot.
- Open the hood and locate the dipstick. It usually has a brightly colored loop or handle, often yellow or orange, though not always.
- Pull it out and wipe it clean. The first pull only coats the stick, so the reading is not reliable yet.
- Reinsert it fully. Push it all the way down until it seats.
- Pull it out again and read it. Hold it horizontally, or flat enough that the oil does not run along the stick.
Reading the marks
Near the tip of the dipstick you will see two marks. They may be two dots, two lines, the letters L and F (low and full), MIN and MAX, or a cross-hatched area. The oil should reach somewhere between them.
- At or near the upper mark: the level is good.
- Between the marks: acceptable. If it is near the lower mark, plan to top up.
- At or below the lower mark: add oil.
- Above the upper mark: the engine is overfilled. Too much oil can foam as the crankshaft whips through it, which reduces lubrication and may damage seals. If it is well over, a mechanic should drain the excess.
The distance between the two marks usually corresponds to roughly one liter or one quart, but check your manual, because it varies by engine.
Judging color and condition
While you have the dipstick out, look at the oil on it. Rub a little between your fingers on the paper towel if you wish.
- Amber to light brown: typical of fresh oil.
- Dark brown or black: common for oil that has been in use. Dark oil does not by itself mean it is worn out, since detergents hold soot in suspension, and many engines darken oil within a short time. Color is a weak guide to remaining life, so go by the interval in the manual.
- Milky or creamy, like a coffee-colored milkshake: may indicate coolant or moisture mixing with the oil. This can be a serious fault, such as a head gasket problem, though a little condensation on the underside of the filler cap after short winter trips is different. Do not keep driving if you suspect coolant contamination. Have a mechanic look at it.
- Gritty or with visible metal specks: a sign of abnormal wear. Get it inspected.
- Smelling strongly of fuel: can point to fuel dilution and deserves a professional check.
Topping up
If the level is low, add oil of the grade and specification the manual lists, as explained in the guide to oil viscosity. Remove the filler cap on top of the engine, usually marked with an oil can symbol, and pour in a small amount, for example a quarter of a liter at a time, using a funnel if needed. Wait a minute for it to settle, then recheck on the dipstick. Repeat until the level is near the upper mark, and do not go over it. Refit the cap and dipstick securely.
If you need to add oil frequently, the engine is consuming it or leaking it. Look for drips under the car or blue smoke from the exhaust, and have it checked. Leaks and consumption are worth fixing before they become expensive.
Warning signs to act on
An oil pressure warning light on the dashboard means you should stop driving as soon as it is safe and switch the engine off. Do not wait until you reach home. Check the level once the engine has settled. If the level is normal and the light stays on, a mechanic should diagnose it, and you may need towing.
Keep a record
A quick note of the date, mileage and any amount added helps you spot changes in consumption. It also helps when you work out when the next oil change is due. If anything about the readings or the appearance seems off, a qualified mechanic can take a look.