If you’re an average DIYer trying to fix up your own lawnmower, but aren’t sure if you should use 10W30 or 10W40 motor oil to lube the blades, this article has the answer you seek. We’ll explain why these numbers are so important, how they relate to your engine, and what you should do if your lawnmower calls for 10W40 oil.
If you’re not familiar with lawn equipment, you might be wondering what 10W-40 oil is. It’s a common type of motor oil used in many engines, including those on lawnmowers.
In the US there are two different SAE grades used for motor oil. 10W-30 is a grade used for gasoline engines and 10W-40 is a grade used for diesel engines. But what about your lawnmower? What type of oil should you use and what would happen if you used the wrong type? We’ll discuss this below.
What does 10w40 mean?
10W40 oil is a blend of 10 parts mineral-based base stock, which are the “W” oils, with 40% synthetic additives – this being the “40”, making it effectively a 10/40 blend.
A straight-weight oil would be called 10W (in other words, just 10 out of 40), but most equipment manufacturers recommend multi-grade oil.
The reason is, the base oils are much thicker when cold, but are thinner at higher temperatures. For example, 10W40 has a viscosity of 9.3 CST@ 40°C (100°C) and 2.6 CST@ 100°C.
Can you use 10w40 in a lawnmower?
Yes, but it is not recommended by most manufacturers. The reason is that the 10W-40 oil is designed to be used in diesel engines and as such has additives that coat internal engine parts as well as prevent corrosion and soot accumulation on pistons etc.
Your lawnmower’s engine will run just fine with this oil, but there are other additives that are used in the oil that is specifically designed for lawnmower engines, so it is generally not recommended.
Before you can determine if you should use 10W40, you need to know what type of oil your lawnmower calls for. It’s important that you match the weight (thickness) of the oil to your engine since different weights are designed for different operating temperatures.
The most common oils used in small engines are SAE 30 and SAE 40. Typically, most small engines will call for 10W-40 oil, but if your lawnmower calls for 10W30 oil you can still use it.
What’s the difference between 30w and 40w engine oils?
SAE 30 is a blend of lighter-weight base stocks with non-detergent additives. Typically, SAE 30 oils have less than 0.25% detergent and no more than 0.8% ash to prevent deposits from forming in the engine oil passages.
In other words, it’s a very basic oil with minimal additives, which is why it’s great for small engines that aren’t going to see much use since you don’t want to build up sludge or carbon deposits.
SAE 40 is a blend of heavier weight base stocks with non-detergent additives. These oils are typically used in automotive gasoline engines that are subject to higher operating temperatures. The tolerances inside the engine are much closer than those on small equipment, so you need an oil that performs well.
What would happen if you used the wrong oil?
Using the wrong oil can cause a number of problems, from lack of performance to complete engine failure. If you use 10W40 in a lawnmower that calls for 10W30, your engine will run hot since it’s being forced to move thicker oil through the passages.
The result is increased fuel consumption and decreased power, but more importantly, the faster moving parts of the engine move this thicker oil and can actually cause sludge to build upon these smaller, faster-moving components.
The worst-case scenario is that your mower’s engine will seize completely if too much sludge or deposits have built up on small moving parts.
In conclusion, always check your manufacturer’s recommendations before buying and using motor oil in your lawnmower. Follow their guidelines for both weight and type, even if you think you know better about what’s best for your engine.
How do I know what type of oil to use on my lawnmower?
The best way to determine what type of oil your mower needs is to consult the manual provided by the manufacturer. If you don’t have a manual, visit a local dealer and they should be able to help. In most cases, you can also call the manufacturer as well.
What weight of oil should I use in my lawnmower?
In most cases, your mower will call for multi-grade SAE 40 motor oil. In other words, it’s usually recommended that your mower be filled with 10W40 or a similar blend of oils. You can usually find this type of oil at most auto parts stores.
Conclusion
There are many different types of oil that can be used in a lawnmower engine, but not all are recommended. You should always check with the manufacturer before filling your engine with any type of oil to ensure proper compatibility.
We hope that you’ve found this article helpful, and if you have any more questions, just let us know in the comments section below.