Like any engine, the one in a combustion engine lawnmower needs care if it is to last a long time. This includes checking and topping up engine oil. To avoid engine damage, it is important to use the correct engine oil for your lawn mower. But which is the ideal choice? Following are the answers.
engine type
The engine type primarily decides which oil is suitable. When it comes to lawn mowers, a distinction is made between a 2- and a four-stroke engine. Special motor oils are offered for both variants, which are also marked as 2- and 4-stroke lawn mower oil. It is therefore important to find out what type of engine the lawn mower has before you buy it.
2-Bars
In a 2-stroke engine, the oil burns with the petrol. Depending on the lawnmower model, the engine oil is added to the petrol in the tank (mixed lubrication) or there is a separate oil tank into which it is filled. It is then fed into the petrol tank by means of an integrated pump during commissioning (separate lubrication). In the latter case, the oil also lubricates the engine at the same time. An oil tank is therefore no indication that it is a four-stroke engine.
A self-mixing two-stroke oil should be used for separate lubrication. Here, the mixing ratio between lawn mower oil and petrol must be taken into account, which depends on the tank and engine size. How high the mixing ratio should be can usually be found in the operating instructions for the lawnmower. A conventional two-stroke oil that is offered specifically for lawn mowers/garden equipment is suitable for filling into an oil tank for mixture lubrication.
4-Bars
Unlike a 2-stroke engine, the engine oil does not burn in a 4-stroke engine and a separate oil tank is always available. It circulates from there and has the sole function of lubricating various areas of the engine. Since it does not run through the fuel lines, there is no requirement for clean combustion. Accordingly, it has different properties than a lawnmower oil for 2-stroke engines. These are similar to automotive oil. There are differences here that a two-stroke oil does not have.
A 4-stroke lawn mower should only be filled with engine oil for 4-stroke engines. In contrast to two-stroke engine oils, they are excellent with the SAE classification. This in turn is divided into different classes, which are based on the respective viscosity.
SAE classification for 4-stroke lawnmowers
SAE is an abbreviation for Society of Automotive Engineers. This is always assigned two number ranges, which refer to the viscosity (thickness) and the appropriate temperature range, such as SAE 10W-30. The classifications apply at international level and are based on test methods in which the stated properties have been established.
The “W” in the SAE classification stands for the flow properties, which play a major role in the temperatures. The lower the number in front of the “W”, the more liquid the engine oil is. When it is cold, it therefore has better flow properties and can take over the function of engine lubrication more quickly after the engine has been started. This minimizes engine wear.
The number after the “W” indicates the resilience of the lawnmower oil when it is hot. As the number increases, the viscosity increases and the oil becomes more viscous.
Ideal SAE-Class
As a rule, a lawn mower is used between spring and autumn. After all, temperatures below zero are hardly to be expected during this period. With modern 4-stroke lawn mowers, however, nothing can go wrong with a single-grade SAE 30 motor oil. It is suitable for temperatures from five degrees Celsius. The following SAE classes also offer examples of a possible class selection:
SAE 10W-30
- For fluctuating temperatures between minus 18 and plus 38 degrees Celsius
- Engine starts better at low temperatures
- Oil consumption increases from an outside temperature of 27 degrees Celsius
SAE 5W-30
- Synthetic Oil
- For use in temperatures down to minus 30 degrees Celsius and heat up to 40 degrees Celsius
- Ideal for continuous lawn mower operation at temperatures below five degrees Celsius
- Improved engine starting at all temperatures
- Less oil consumption
SAE 15W-50
- Fully synthetic oil for lawn mower engines
- For temperatures between minus six degrees Celsius and 55 degrees Celsius
- Ideal for frequent lawn cutting in regions with prolonged high temperatures
- Enables fuel savings of 1 to 6 percent
API Specifications
In addition to the SAE classification, other abbreviations/letters can usually be found on the packaging, which often cause confusion. These are so-called API specifications. API stands for “American Petroleum Institute”, through which the classifications were made as specifications for any minimum requirements. Lawnmower oil for 4-stroke engines or petrol engines can be recognized by the letter “S”, while “C” is used for diesel engines.
This is followed by another letter that indicates the quality level. The higher the letter is in the alphabet, the higher the quality of the motor oil – example SL is of higher quality than SG. The maximum quality level is currently reached with SN. When buying, you should therefore make sure that the engine oil for the lawnmower is of good quality at least API-SG, because the better the oil, the better the lawnmower engine works and the longer it lasts.
Differences: (fully) synthetic and mineral oil
Buyers are often faced with the question of what the differences are between semi-synthetic, fully synthetic and mineral oil and what is the better choice than lawnmower oil. Following are the differences:
- Synthetic oil is more expensive than mineral oil (due to manufacturing reasons)
- Basically more optimal flow behavior at low temperatures, which protects the engine during cold starts
- Synthetic oil has a higher temperature stability
- Synthetic oil performs better than mineral oil
- Higher quality than mineral oil
car oil
If there are still engine oil residues from the last refill of the car or if a car oil is currently being offered cheaply, you should not be tempted and ultimately never use it for a lawnmower.
A motor vehicle oil is usually a so-called multigrade oil. This means that the temperature fluctuations of the different seasons and trips to other climate zones can be compensated. The multigrade oil is therefore so important for cars so that the lubricating film does not tear through. If the motor vehicle oil were to be used in a lawn mower, which is normally only put into operation in warmer temperatures between spring and late summer, this can significantly accelerate the wear of the lawn mower engine. An exception is the use of car oil in lawn tractors, which are also used in winter. In this case, for example, an SAE 5W-40 fully synthetic oil is recommended.
