Skip the auto shop - Our mechanics make house calls

Why Are 5W-30 and 5W-20 Oils So Common?

Engine oil cap

In terms of taking care of your car, there's not much more important than changing oil. The reason 5W-30 and 5W-20 motor oils are so common is because they work very well with a wide range of engines. Most often, these types of oils best cover the range of possible temperatures, with a 5W-20 oil more geared toward colder climates and a 5W-30 oil more appropriate for warmer temperature extremes. For the most part, either one should work just fine in an engine regardless of the prevailing temperatures.

The difference between 5W-30 and 5W-20 motor oil

The main difference between 5W-30 and 5W-20 motor oil is that the latter is less viscous (or thick). When used in a vehicle's engine, 5W-20 oil creates less friction due to its thinner viscosity, meaning it causes less drag across engine parts like the crankshaft, valvetrain, and pistons. This can provide a slight bump in fuel efficiency.

The thinner nature of 5W-20 oil also allows the oil pump to move it from the oil pan to the rest of the engine more easily. This makes 5W-20 preferable for very cold climates, when having thinner oil that can flow easily on start-up is important. Where 5W-30 comes into play is in hotter climates where thin oil tends to break down under higher temperatures. This translates into the strength of the 5W-30 oil keeping it from breaking down as quickly as the 5W-20 oil, providing better overall engine part protection.

Single viscosity vs. multiviscosity oil

Designed to operate in a multitude of temperature ranges, a multiviscosity oil represents one of the best motor oils for cars. The single viscosity oils of the past provided protection during either hot or cold weather, depending in large part on the weight, or lower temperature extreme at which they operated. This usually meant using a 5W-30 oil in the fall and winter and a 10W-30 in the spring and summer.

A multiviscosity oil, on the other hand, uses special additives to improve the viscosity of the oil. Called, ironically, viscosity improvers, these additives expand as the oil heats up, providing a higher viscosity at warmer temperatures. After the oil cools, these improvers shrink, making the oil thinner, best for use during cooler engine operation.

How oil additives help clean and protect an engine

Oil manufacturers use additives in oil for cars to improve the performance of the oil when it comes to lubrication. In addition, some other affects of additives in oils include cleaning engine deposits from engine parts, inhibiting corrosion or rust inside the engine, and keep the oil from breaking down as bad either due to oxidation or extreme temperatures.

Which oil should vehicle owners use?

When looking for a motor oil that works best in your vehicle, keep certain factors in mind. While not a lot of difference exists between the protection provided by a 5W-30 AND 5W-20 oil, there is a slight difference in the viscosity levels of each. The thicker 5W-30 should see a slight advantage when operating at higher temperatures, while the thinner 5W-20 oil should provide better engine protection at lower temperature levels and has the added benefit of slightly improving fuel efficiency.

The flexibility of today's synthetic motor oil means that both 5W-30 and 5W-20 oils work equally well to protect your engine regardless of the climate or season. Castrol provides a wide range of multiviscosity oils to suit your engine. YourMechanic brings top-quality Castrol synthetic or conventional oil to every mobile oil change.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
How to Transfer a Car Title in Idaho
In order to prove ownership of a car, you must have the title. However, when a car is sold, given away or inherited, the title needs...
How to Get a Louisiana Driver's Permit
s licensing program. The first step in this program is to obtain...


Related questions

Q: Changed the oil and now there's a tick coming from my engine

Hello, thank you for writing in. Cost commonly the issues with ticking noises in the engine stem from the valves and lifters that control the intake and exhaust flow through the engine. The engine oil lubricates and supports all of...

Q: I took the car to the dealership for a oil change and they said the CV Axle (whatever that is) needs to be replaced. how long can I drive

Your car's CV axle is a joint that connects the transmission drive shafts to the wheels and is responsible for the transfer of power from the transmission to the wheels. The CV joints take a lot of abuse from the...

Q: Changed the oil yesterday. Started car this morning and it is pouring out white smoke. Gasket? Too much oil? Not losing coolant

The 5W-30 oil should be removed from the engine because that viscosity is not recommended for your car. However, the wrong viscosity oil does not account for the smoke. You can verify whether the oil level is too high, or...