Trying to figure out all the pros and cons of different engine oils can be quite an undertaking. With all of the different types of engines out there, and all of the motor oil options sold in stores, there are a ton of things to keep in mind when determining what oil to use and where. Recently I’ve noticed a bunch of talk about 20w50 oil and I decided to look into its applications a bit more. After doing some digging, I figured I should write a bit about 20w50 oil disadvantages in the context of lawn mower engines.
20w50 Oil Disadvantages (The Short Version)
The main 20w50 oil disadvantage is that it is too thick for most small engines. Oil that is too thick or too thin for the engine that it is used in will cause excess stress on engine parts. Using 20w50 in a mower or other lawn equipment will result in loss of horsepower, more fuel consumption, and increased internal friction.
The Cons of Using 20w50 Oil in Your Lawn Mower
After painting a quick picture of 20w50 oil disadvantages, I think it’s a good idea to discuss these cons in more detail. Being aware of the downfalls of 20w50 should give you a general idea of why the oil you use in your engines is so important, and also help you figure out when and where not to use heavy-duty oils like 20w50.
Extremely heavy/thick oils are used in engines that get extremely hot, or generate tons of power. If you put an overly thick oil into a smaller engine, there will be some consequences. The main ones are added stress on the engine parts, a decrease in the amount of horsepower produced, and worse fuel economy. Let’s take a look at each one.
Stress on the Engine
Oil circulates throughout 4 cycle engines and lubricates all of the moving parts as it goes. You don’t need to know a ton about engines to know that there are quite a few moving parts. The thickness of the oil in the engine matters a lot because it determines how well the parts can be lubricated.
Oil like 20w50 is much thicker than the average 30-weight oil that is recommended for most lawn mower engines. Using 20w50 in a lawn mower places all of the engine parts under more strain than usual as they fight through a more viscous liquid. On top of this, the engine parts don’t get lubricated as effectively.
Because small engines don’t get as hot as larger engines, 20w50 oil remains a bit too sludge-like and won’t be able to lubricate all of the hard-to-reach places inside the engine properly.
Less Horsepower
Along with increased wear and tear on engine parts, a decrease in horsepower is something you can expect when using 20w50 in a lawn mower engine. Because there is more internal friction from the engine’s parts pushing through the oil, the engine can’t produce as much power as it normally would.
Small engines aren’t designed with the use of extra viscous oil in mind, and they can be somewhat sensitive to changes in the type of oil they run with.
Increased Fuel Consumption
Another result of added stress on the engine and loss of power is worse fuel economy. This is probably the least threatening of the 20w50 disadvantages listed here, but it’s worth noting. Paying attention to the number of hours you can get from each tank of gas is a good idea because if you notice increased fuel consumption you could have an engine problem on your hands.
Running out of gas more quickly than normal can be a big pain, especially if you have a large yard and use a riding lawn mower. Plus, who doesn’t want to make a tank of gas last as long as possible?
Summary
All in all, there are a number of disadvantages to using 20w50 oil in a lawn mower. Because of this, I wouldn’t recommend using it in any small engine equipment at all. The highest weight oil that I’ve heard being recommended for small engines is rated at a viscosity of 40. Plus, this is only really suggested for people that might be mowing or doing other lawn care somewhere that consistently reaches over 90 degrees during the summer. 20w50 oil might be useful in some automotive cases, but it wasn’t designed for a lawn mower’s engine.
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