A Handy Guide to the Different Types of Motor Oil
Motor oil is confusing and using the wrong type can result in costly engine damage. Here we'll explain the types so you can make the right choice.
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Unless oil soluble dyes are added to change its color for identification purposes, all lubricating oils can look and feel the same. This can be a problem.
When I first started working at a car repair shop (in 1969!), we stored motor oil in 55-gallon drums. We hand-pumped it into oil dispensing funnels, then added it to an engine after an oil change. This was fine until a drum filled with hydraulic oil was mislabeled as 10W-30 motor oil. Thankfully, we quickly caught the error and replaced the oil and filter in every car. Except one.
We contacted the unlucky owner immediately and towed the car back the next day. The engine was already experiencing a slight knock, but fortunately a new oil pump and the right oil resolved the issue. Had it been driven any longer, the engine damage would have been inevitable and expensive. Today a new six-cylinder engine costs around $5,500, plus $2,000 for labor.
Long story short, selecting the right oil today shouldn’t be mystifying. We can help you make the best choice for your vehicle or power equipment.
What Is Motor Oil?
Motor oil is an engine’s lifeblood. It cleans, lubricates, cools, cushions and protects engine parts from wear. Motor oil also holds in suspension sludge, harsh chemicals, contaminates and abrasive particles that cause engine wear.
Read the labels
Choose an oil matching the vehicle’s or original equipment manufacturer’s (OEM) recommended viscosity and service rating.
Viscosity is an oil’s ability to flow at different temperatures. Multi-weight oils like SAE 5W-30 (the “W” stands for winter weight) perform well over wide temperature ranges. SAE 0W-30 flows better than 10W-30 at lower temperatures.
Single-weight oils like SAE 30 have narrower temperature ranges. Keep this in mind if the temperature fluctuates greatly where you live — say, from 0 degrees in the winter to 100 degrees in the summer.
The oil service rating/category indicates its performance level. Introduced in May 2020, SP is the current rating. It aims to reduce engine emissions and protect engines using fuels containing ethanol. The container should clearly display the American Petroleum Institute (API) standards rating seal, the Society of Automotive Engineers (SAE) viscosity grade/weight and the manufacturer’s usage label.
Also know whether you’re dealing with a four-stroke or two-stroke engine. In a two-stroke engines, gasoline and motor oil are mixed together. Two-stroke engines (aka crankcase compression engines) run at extremely high revolutions per minute (rpm) and temperatures. They’re found in scooters and yard equipment like string trimmers, chain saws, and leaf blowers.
Different Types of Motor Oil
Virtually all new motor oil is a transparent yellowish amber, with a consistency of olive oil. Motor oils are not interchangeable. There are significant distinctions between the type of oil you should use in your car, truck, motorcycle or power equipment.
Always use a motor oil that strictly adheres to the vehicle or OEM specifications. Oil specs are found in the owner’s or user’s manual.
Also take into consideration the type of conditions, such as city vs. highway driving or off-roading, as well as temperature, dust and dirt. For power equipment, also keep in mind how long you’ll be using the tool.
Conventional motor oil
All motor oil comes from the ground as crude (base) oil. Then it’s refined to remove impurities, and blended with additives that neutralize sludge and inhibit corrosion. Conventional oils are best for:
- Cars and light trucks that don’t need synthetic motor oils;
- Four-stroke power equipment, single and multiple cylinder engines (older lawn mowers, power washers, generators, outboard motors, snowblowers) that don’t need synthetic oil;
- Two-stroke conventional motor oils are specially refined for small engine gasoline powered equipment.
High-mileage motor oil
Formulated for vehicles with 75,000 miles or more, high mileage motor oil contains enhanced additives that cause internal and external O-rings and gaskets to swell, potentially reducing oil leaks and oil burning in older engines. Use in high-mileage cars and light trucks.
Full-synthetic motor oil
Full-synthetic motor oil delivers ultimate engine protection. Extensive distilling and refining processes remove more impurities. Added chemically enhanced friction modifiers offer exceptional engine protection not found in conventional or synthetic blended oils.
Synthetic oil, although superior, is not recommended for older model vehicles and equipment that takes conventional oil. Use in:
- Modern cars and light trucks in all engine configurations, including turbocharged and diesel;
- Modern motorcycles that are air- or water-cooled without a wet clutch;
- Newer two- and four-cycle air cooled power equipment like portable concrete saws, snowmobiles, jet skies unless not recommended by the OEM.
Synthetic blend motor oil
Synthetic blend motor oil mixes conventional oils and synthetic compounds. The best of both worlds, blended oil provides excellent engine protection at a lower cost than full synthetics. Use in:
- Cars and light truck engines without turbocharged or diesel engines;
- Motorcycles with air- and water-cooled engines;
- Most air- and water-cooled four-stroke power equipment engines with single or multiple cylinders (check the OEM recommendation first).
Racing motor oil
Racing motor oils are a full synthetic that won’t break down under high-revving, full throttle engine acceleration and load. These oils are compatible with air- and water-cooled engines. They improve motorcycle wet-clutch performance by eliminating “friction modifiers” like molybdenum that could lead to shifting difficulties. Use in:
- Racing motorcycle engines and drivetrains (check the OEM first);
- Four-cycle small engines like log splitters, pump motors, compressors and go-carts;
- Four-cycle air-cooled small engines and long-running back-up generators.
Marine motor oil
Motor oil for marine engines comes in conventional or full synthetic, specifically blended for two- or four-stroke high-revving marine engines. Additives in marine motor oils offer enhanced corrosion protection and resist thermal breakdown under extreme summer temperatures and severe engine loads.
Choose a brand compatible for boat engines with or without catalytic converters. Use in stern-drive and outboard motors.
Why Do Some Manufacturers Recommend Oil Brands?
To ensure their products are protected and safeguard consumers against premature failures covered by their warranties, OEMs will recommend specific motor oil brands that meet their exacting standards and ratings. Usually, it’s an oil branded under their name.
However, the Federal Trade Commission enforces the Magnuson Moss Warranty Act, which prohibits companies from “conditioning a consumer product warranty on the consumer’s using any article or service which is identified by brand name unless it is provided for free.”
So, although you’re not required to use the manufacturer’s oil, it’s highly advised you do while under the factor warranty. If you go with another brand, ensure it meets or exceeds the manufacturer’s specs. To protect yourself, retain all receipts and keep good records of all maintenance performed on your car or equipment, whether you or your mechanic performed it.
If unsure a specific brand or type of oil meets OEM specs, search online. Or check with your dealer’s service department or approved repair facility. They should have a list of approved motor oils for your engine.
Can the manufacturer tell if the recommended oil wasn’t used?
Yes. Although an oil analysis most likely cannot identify a specific brand, it can verify fluid properties, contaminates and wear debris, as well as measure type, viscosity and additive levels.
Manufacturers, especially third-party after-market warranty companies, will deny an engine repair claim and void the warranty (for the engine at least) if they determine you used non-compatible motor oil. Why risk going with a non-recommended oil that could cause premature engine failure and cost you thousands of dollars? After the warranty expires, you can experiment if you wish.