How to Mix SAE 10W-30 With 5W-30

Written by John Kibilko

20 May, 2010

With the advent over the past several decades of quick-oil-change shops, most automobile owners no longer change their own oil. But they often find the need to add oil between changes to maintain oil levels and ensure engine performance. Car owners may not remember what grade of oil is in their cars, or they might have a different brand or grade on hand than what's currently in their engines. They worry about mixing 5W-30, for example, with 10W-30 and how to do it. This is a simple and safe process.

Determine the type of oil currently in your car. Check your service records or read the label on the can of oil sitting on the shelf in your garage.

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Open the hood of your car and remove the oil dipstick. Take note of the fluid level and determine how much oil you need to add (the dipstick usually will indicate the proper amount to add, such as “ADD 1 QUART” or “FILL TO HERE”).

Wipe the dipstick clean with a rag and replace into the receptacle.

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Remove the oil filler cap and place a funnel in the opening.

Pour the proper amount of oil into the oil fill reservoir.

Remove the dipstick and take another reading. Continue to add oil to the oil fill reservoir until you achieve the proper level.

Replace the dipstick and secure the oil filter cap. Close the hood.

Start your car and check the oil level again while the engine is running.

Tips

If your car contains a typical multi-grade oil, such as 5W-30 or 10W-30, you can use most any multi-grade oil to “top off” your oil and bring it up to a proper level. Mixing the viscosity of oil has no effect on the engine. 5W30 and 10W30 are very close in viscosity. Your owner's manual will specify the type of oil to use in your car–such as SAE 5W-30.

“SAE” is the Society of Automotive Engineers, which created a standard for identifying the viscosity characteristics of engine oil. “W” stands for “winter” and indicates the oil’s low temperature viscosity properties; 30 refers to the high temperature or operating viscosity properties. This is an example of a “multi-grade” oil, which allows for operating an engine at both cold and hot temperatures.

Warnings

Although most multi-grade motor oils are interchangeable and can be used in combination, be wary of randomly mixing mineral (“natural” oil derived strictly from petroleum) and synthetic oils. While mixing multi-grade oils of these two types will rarely cause problems, it’s best to check with an expert beforehand.

Mixing oils such as 5W-30 and 10W-30 should be limited to between-oil changes and in emergencies. Your car’s manufacturer has determined the proper oil for your car. When conducting a total oil change–whether it’s every 3,000 miles or every two years–follow your owner’s manual guidelines.