10w30 instead of 5w20

If you’re wondering if you can 10W-30 instead of 5W-20, then you’ve likely found yourself in a storm of confusing motor oil jargon. While it’s understandable, you need to know that using the wrong viscosity of oil in your car can cause serious engine damage.

Of the two, 10wW-30 is thicker and if your car is engineered to run on 5W-20, it will be harder for the oil pump to pick up. This can leave some oil galleries and moving parts under-lubricated, with potentially disastrous long-term consequences.

To help you understand if you can use 10W-30 in place of 5-20 in an emergency, we’ll have to take a look at the differences between these two oils. We’ll also take a look at what could happen if you run your engine on the wrong viscosity of oil for too long! Along the way, we’ll need to ask and answer a few important questions.

Why Is Motor Oil Viscosity Important

When choosing the right type of motor oil viscosity is a critical factor. The higher the viscosity, the thicker the motor oil. Yet if the viscosity is too low, the oil might not have enough lubricating properties to prevent friction damage in the relationship between the pistons and the cylinder walls.

The motor oil has enough of a flow rate to be easily picked up by the oil pump. Yet also has thickness and lubricating properties to resist excessive friction between all the engine’s moving parts.

What Do Motor Oil Numbers & Letters Mean?

The letters on a jug of motor oil indicate the viscosity or “Weight” of the oil. This is the oil’s resistance to flow. The lower the number, the lower the viscosity and the easier the oil is for the oil pump to draw up through the oil filter to distribute through the engine’s oil galleries.

The number to the left of the W indicates the oil’s viscosity in cold temperatures. The second number indicates the viscosity of the oil, once the engine has warmed up to its normal operating temperature.

Modern multi-weight oils with different viscosities based on temperature provide equal protection in cold weather, and at start-up. They also ensure that the oil will still provide sufficient lubrication for all the moving parts once it’s warm and thin.

1. The Viscosity & Properties of 5W-20

The Viscosity & Properties of 5W-20

5W-20 is a low-viscosity motor oil, that you find in vehicles that need to run in cold temperatures. You tend to see it most in light-duty vehicles with gasoline engines that need help minimizing engine deposits while reducing wear and tear.

Temperature Considerations

One of 5w-20’s strengths is great start-up performance at low temperatures. Its low viscosity allows the oil to flow freely. The oil pump picks it up quickly and it flows through the galleries thoroughly to rapidly lubricate all the engine’s moving parts.

Lubrication

5W-20’s thinner viscosity produces less friction on engine parts like the crankshaft and pistons in cold conditions. This helps save energy and maintain fuel efficiency, which also translates into slightly lower exhaust emissions.

Availability

One of the problems with 5W-20 is that it isn’t as widely available as some other oils. If your car is supposed to run on 5W-20, but you need to drive it to a southern state, you might want to bring a few extra quarts with you just in case.

This can keep you from needing to improvise with another oil should you have a small leak.

2. The Viscosity & Properties of 10W-30

The Viscosity & Properties of 10W-30

10W-30 is the most commonly used oil in most North American domestic vehicles. This multi-weight oil is prized for its ability to be picked up easily by the oil pump in cold conditions. Then it still thoroughly lubricates the engine’s moving parts, even once the car is warmed up.

Temperature Considerations

10w-30’s multi-weight viscosity makes it suitable for a variety of weather conditions. It performs reasonably well in both cold and hot conditions. The 10 weight when the engine is cold is still relatively easy for the oil pump to draw from the oil pan, while easily distributing through all the galleries.

Lubrication

With a cold viscosity of 10 and a warm viscosity of 30, it does a good job of lubricating in warm and cold conditions. Yet it doesn’t have much resistance even when the engine is running hot, which isn’t true of heavier oils. This helps maintain good fuel efficiency and keeps exhaust emissions to a minimum.

Availability

10W-30 is the most common type of motor oil used in North American vehicles, and you can find it just about anywhere. This is great if you’re on a long road trip vacation and you need an oil change, or you notice your oil is low, as you pull into a small gas station.

What Happens If You Use 10W-30 Instead of 5W-20?

Using 10W-30 instead of 5W-20 is the sort of thing you should only do in an emergency situation, or if your car’s owner’s manual lists 10W-30 as a viable oil. This is highly unlikely given the viscosity differences between them.

Yet, let’s imagine a situation where you’re driving a car engineered to run on 5W-20, and it’s severely low on oil, but the only thing you can find is 10W-30. You need to get a few miles home or to the mechanic, and getting a tow is out of the question. What would happen if you were to use 10W-30 instead of 5W-20?

Start-Up & Cold Performance Problems

10W-30 has a thicker viscosity when it’s cold and the engine isn’t up to normal operating temperature. This makes it hard for the oil pump to pick it up when you first start the engine or when the outside weather is chilly.

When you first start the car, there might not be a sufficient level of lubrication on the moving parts. The oil pump might not be able to distribute the thicker 10W-30 oil through all the galleries in the engine block and cylinder head.

Once the engine warms up to normal operating temperature, the viscosity of the 10W-30 should be thin enough to maintain the minimum level of lubrication for the essential moving parts. Unfortunately, this could take the better part of 10 minutes depending on the outside weather!

1. Excess Engine Wear

Excess Engine Wear

10W-30’s inability to properly lubricate the engine when it’s cold will cause excess wear on the moving parts. Especially in the cylinder walls as well as the piston rings, and the connecting rods.

When cold, 10W-30 in an engine meant to run on 5W-20, might not be able to pass enough oil through the wrist pin or gudgeon pin. This will leave the connecting rods dangerously under-lubricated.

2. Poor Fuel Economy

Poor Fuel Economy

When you use 10W-30 instead of 5W-20 there will be more resistance within the engine, which can gradually affect fuel economy. This is because 5W-20 is lighter with lower viscosity and the engine was designed to run with this level of reduced internal friction.

The thickness of 10W-30 makes all the moving parts in the engine work a little bit harder. You get less power per stroke and have to use more gas to compensate.

3. Warranty Concerns

Another risk of using 10W-30 rather than 5W-20 is that it could void the car’s warranty coverage. Most automotive warranties and service plans have fine print language stating that you will be responsible for any repair costs for using the engine abusively.

They will then easily argue that using the wrong viscosity oil is abusive use. They might still honor other components of the warranty, like defects in the body panels or the electronics, but any engine repairs will likely fall on your shoulders.

4. Poor Engine Protection Additives

Poor Engine Protection Additives

Some oil companies use different additives for 10W-30 than they do for 5W-20. This can cause a myriad of problems from the engine not having the additives it normally runs on. Not to mention the risk of partially clogging the oil filter.

What To Do If You Use 10W-30 Instead of 5W-20?

If you have to use 10W-30 instead of 5W-20 in an emergency situation, you need to drain the oil as soon as safely possible. Ideally, you would get home, or to a mechanic or auto parts store carrying 5w20, and change the oil before restarting the car when it’s cold.

This will minimize any potential damage that could happen if you run 10W-30 through a cold engine at start-up.

You’ll also need to replace the oil filter to ensure all traces of the 10W-30 are cleared out of the system. If the car is less than 10 years old, you might want to perform an oil flush before the final oil change, just to make sure all the galleries and pins are cleared of any residual 10W-30.

Best Alternative Motor Oils for 5W-20

There are better emergency oil alternatives than 10W-30 for a car engineered to run on 5W-20. If you absolutely need to run your engine with a different oil, you might want to consider one of the following.

5W-30

5W-30

It offers the same cold start-up viscosity of 5W-20, but it’s slightly thicker once the engine has come up to operating temperature.Some cars that run on 5W-20 state that you can safely use 5W-30 in the owner’s manual. It’s also a relatively common oil that you can sometimes find right next to the cases of 10W-30 in an auto parts store.

0W-20

0W-20

This motor oil is slightly thinner than 5W-20 and will have no problem offering cold-start protection without affecting fuel economy. There might be no effect on the engine performance when running in cold weather.

0W-30

0W-30

This type of motor oil offers the same easy pickup on cold/start-up as 0W-20. However, it has a slightly higher viscosity once the engine has warmed to normal operating temperature.

Frequently Asked Questions

What Are SEA Oil Grades?

The SAE symbol you see on most motor oils stands for the “Society of Automotive Engineers.”They work with the American Petroleum Institute (API) to determine and maintain motor oil standards. Their information is published to provide the technical specs for a wide range of oils. Their stamp or logo on a quart of motor oil lets you know that the oil inside meets their technical standards, for the stated viscosity.

Is it OK to mix 10W-30 and 5W-20?

Mixing oils like 10W-30 and 5W-20 is never a good idea. Not only do they have two different viscosities, but the chemistry of their additives could potentially react. This can cause additives and other particulate matter to fall out of suspension. The oil filter could clog, which would rob the engine of any oil, leading to severe friction and engine damage problems.

When is it acceptable to use 10W-30 instead of 5W-20?

The only time it’s reasonably acceptable to use 10W-30 instead of 5W-20 is when it’s an emergency, and there’s no 5W-20 available. This might be a camping trip in a remote location, you’re driving back and suddenly an oil seal blows out. The backwoods gas station only has 10W-30. So, you use it to keep the already warm engine lubricated while you drive a few miles to a main road where you can get a tow truck.

Conclusion

You should only use 10W-30 instead of 5W-20 in an emergency situation. The risk of damaging the engine is high. Especially when it’s cold.

The oil pump, oil galleries, and narrow confines like the lubricating ports of the connecting rods are designed to run on the thinner 5W-20. In some instances, 10W-30 might not be able to pass through the galleries and lubricate the connecting rods at all when the engine is cold.

If you do need to use 10W-30 instead of 5W-20, you should only do so for as long as you need to get to safety. After that, a complete oil flush and oil change are needed to extract all traces of the incompatible oil.

Jason Farrell

Written By

Jason Farrell

Jason Farrell is a certified master technician, the editor of Mechanic’s Diary in Pittsburgh, Pennsylvania. He is ASE (Automotive Service Excellence) certified and earned a Bachelor’s Degree in Automotive Technology from Pittsburg State University. With nearly 18 prior years of experience in the automotive field, he has extensive knowledge about Domestic, European, and other foreign makes and models of cars and light trucks. Jason’s experience working as a technician and service manager at dealerships, gave him the experience and know-how of most aspects of inspection, diagnosis, and repair from engine and drivability to electrical, HVAC, brakes, steering and suspension and everything in between.

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