Engine oil primarily lubricates moving parts to reduce friction, preventing excessive heat buildup and mechanical wear. Proper oil levels also assist in cooling the engine and carrying away combustion byproducts, keeping internal components clean. Maintaining the correct oil level is a preventative measure against expensive engine failure.
Essential Pre-Checks
Before checking the oil level, prepare the vehicle for safety and accurate measurement. The engine must be turned off and allowed to cool slightly, as hot oil can cause severe burns. Waiting five to ten minutes allows the oil circulating in the upper engine components to drain back into the oil pan.
An accurate reading requires the vehicle to be parked on a level surface, since an incline can skew the oil level reading. The parking brake must be firmly engaged to prevent unintended movement during the check.
Using the Dipstick
Locate the dipstick, which typically has a brightly colored handle (often yellow or orange) protruding from the engine block. Pull the dipstick completely out of its tube and use a clean rag or paper towel to wipe away all the oil clinging to the measuring end.
Reinsert the clean dipstick fully into its tube until seated, then immediately pull it out a second time. The tip is marked with indicators, usually lines or a cross-hatched area, representing the minimum and maximum acceptable oil levels. The oil film on the second pull should fall between these two marks.
If the oil level registers below the minimum mark, the engine requires additional oil. The distance between the minimum and maximum marks often represents approximately one quart or one liter, which helps estimate how much oil is needed to reach the full range.
Choosing and Adding the Oil
Selecting the correct lubricant is crucial when topping up the engine oil, as using the wrong specification can cause long-term wear. The appropriate oil type is detailed in the vehicle’s owner’s manual, specifying both the viscosity (e.g., 5W-30) and the required industry standards (API or ACEA rating).
The viscosity rating, such as 5W-30, describes how the oil flows at low temperatures, represented by the ‘W’ number, and at the engine’s operating temperature, represented by the second number.
Locate the oil filler cap, usually found on the top of the engine and marked with an oil can symbol. Remove the cap, which exposes the opening leading to the crankcase. To prevent spills, place a clean funnel securely into the filler neck before pouring.
Pour the oil slowly into the funnel, adding a small amount at a time, especially if the oil level was only slightly below the minimum mark. This measured approach helps prevent the mistake of overfilling the system. Overfilling the crankcase can cause the spinning crankshaft to churn the excess oil into an aerated foam, called frothing, which reduces the oil’s lubricating effectiveness and can damage seals.
After adding a small amount, such as half a quart, wait a few minutes for the new oil to settle into the pan. Recheck the level with the dipstick. Repeat this process of adding small amounts and checking until the oil mark sits between the minimum and maximum indicators.
Finalizing the Top-Up
Once the oil level is within the acceptable range, remove the funnel and firmly secure the oil filler cap back onto the engine. Wait a few minutes for the oil to settle before performing a final check with the dipstick.
Any oil spilled onto engine components during pouring should be carefully wiped clean with a rag. Residual oil can burn off when the engine heats up, creating smoke and a distinct odor.