Walk into a parts store and you will find a wall of bottles with different numbers on them. You do not have to guess. Four places will tell you what type of oil your car takes, and the first two come straight from the people who built the engine.
Short answer: open the owner’s manual and look for the recommended oil viscosity and performance standard. The oil filler cap under the hood often shows the viscosity as well. Buy oil whose container shows the same viscosity grade and meets the same standard.
Four places to check
| Place | What it tells you | How reliable |
|---|---|---|
| Owner’s manual | Recommended viscosity, required standards, sometimes alternatives for hot or cold climates | Best source |
| Oil filler cap under the hood | Often the recommended oil weight, printed on the cap | Quick check, confirm in the manual |
| Label on the oil container | The viscosity grade and the standards the oil meets, so you can compare with the manual | Use it to match, not to decide |
| Dealer or parts store | Which oils meet your automaker’s standards | Good if they look up your exact engine |
AAA calls the oil cap the easiest method, since the recommended oil weight is usually displayed there. If it is not, the owner’s manual lists the manufacturer’s recommendation and the change intervals. Consumer Reports adds that the manual may suggest a different oil for hot or cold climates, and that a dealer or most auto parts stores can tell you which oils meet the automaker’s standards.
How to read the numbers
A grade like 5W-30 is a viscosity grade set by SAE, a measure of how well the oil flows at certain temperatures. According to AAA, the number before the W shows how easily the oil flows when the engine is cold, and a lower number means it flows faster. The number after the dash describes the oil once the engine is warm, and a higher number means thicker oil at operating temperature.
Consumer Reports calls viscosity the key factor: the most important thing is oil of the right thickness for your engine. Oil that is too thick or too thin may not protect the engine properly, which can lead to costly damage. If the recommended oil is not available, the manual may list an acceptable alternative weight. Do not swap grades on a hunch.
The quality standard matters too
Viscosity is half of the answer. The other half is the performance standard. The American Petroleum Institute (API) service symbol, often called the donut, shows the category. The “S” categories cover gasoline cars, vans and light trucks, and the “C” categories cover heavy-duty and diesel vehicles. API says to follow the vehicle manufacturer’s recommendation for both the SAE viscosity and the ILSAC or API performance standard.
Some automakers use their own standards, which do not always match SAE or API, according to Consumer Reports. It also notes that synthetic oil is often required because standard motor oil cannot meet many of these standards. If your manual names a specific approval, look for it on the container.
Synthetic, blend, conventional or high-mileage
AAA describes the options this way: synthetic oil is chemically engineered to have more uniform molecules and handles extreme heat and cold better than conventional oil, a synthetic blend mixes both, and high-mileage oil is suggested for engines past 75,000 miles because it contains additives meant to reduce oil burn-off and prevent gasket leaks. Which one you choose is a second decision. First, it has to meet what the manual requires. For intervals, see how often to change oil and synthetic versus conventional intervals.
Mixing brands and topping up
Brand matters less than getting the right weight and standard, according to Consumer Reports. API adds that if you mix oil brands, you should use the same viscosity grade and API service category. The same rule applies to a top-up between changes.
Write it down once
After the next oil change, save the grade and standard so you never have to search again. In Badger you can add the visit as an expense with its mileage and keep a note of the oil used, and the maintenance schedule will remind you when the next change is due.
Common questions
How do I find out what oil my car takes without the manual?
Check the oil filler cap under the hood, which often shows the recommended weight. A dealer or most auto parts stores can also tell you which oils meet your automaker’s standards if you give them the exact vehicle and engine.
What does 5W-30 mean?
It is an SAE viscosity grade. The number before the W relates to how easily the oil flows when the engine is cold (lower flows faster). The number after the dash relates to the oil when the engine is warm (higher is thicker).
Can I use a different oil weight than the manual says?
Not by guesswork. Oil that is too thick or too thin may not protect the engine. If the recommended oil is not available, the manual may list an acceptable alternative weight.
Does the brand of oil matter?
Less than the weight and the standard. Consumer Reports says brand matters less than using the right weight of oil that meets the required standards.
