Lawn mower oil, also known as engine oil, is a vital fluid that helps keep your mower’s engine running smoothly. But how long does lawn mower oil actually last before it needs changing? Here’s a look at the shelf life of mower oil and when you should replace it.
Quick Answers
– The typical oil change interval for lawn mower engines is 50 hours of runtime or one mowing season, whichever comes first.
– Unopened oil can last 2-3 years on the shelf if stored properly.
– After opening, oil will last about 1 year with moderate use before degrading.
– Use oil designed for air-cooled small engines in lawn mowers.
– Check oil levels regularly and top up if needed.
– Change oil more frequently under heavy use or high heat conditions.
– Dispose of used oil properly – never dump down drains or on the ground.
How Long Can Unopened Lawn Mower Oil Sit on the Shelf?
Unopened, factory-sealed oil has a long shelf life. The oil itself does not expire or “go bad” for 2-3 years typically if stored properly.
The key is to keep the oil in a climate-controlled area away from direct sunlight, moisture, and extreme temperature swings. A good storage temperature is around 70°F. If the oil bottle has been subjected to high heat or freezing temps for an extended time, its quality can deteriorate faster.
Check the bottle for an expiration or ‘best used by’ date if you’ve had it sitting around for a while. As long as it was stored correctly, oil is usually fine to use for a few years past the date on the bottle. But the sooner it’s used, the better.
One thing to note is that some oil additive packages can separate or fall out of suspension over time. Giving the bottle a good shake before use can help re-mix the additives.
How Long Does Lawn Mower Oil Last After Opening?
Once opened, the clock starts ticking faster on lawn mower oil. With exposure to air and impurities, opened oil will gradually oxidize and break down during use and when sitting in the engine between mowings.
For moderate lawn mower usage, most experts recommend changing oil at least once per year as a precaution, even if the total engine run time is less than 50 hours.
Oil breakdown can happen faster if subjected to frequent short-run cycles, where the oil does not get fully heated. Prolonged high temperature operation can also degrade oil more rapidly.
Using the “sniff test” on used oil can give you an idea of its condition. Good oil should have a smooth, slippery feel and a light petroleum smell. If it seems thin and watery or has a burnt, acrid odor, it’s definitely time for a change.
What Type of Oil Should Be Used in Lawn Mowers?
Using the proper oil designed for air-cooled small engines is important for longevity and performance.
Look for oil that meets API (American Petroleum Institute) service class SJ or higher. These oils contain anti-wear additives and detergents formulated for 2-stroke and 4-stroke mower engines.
Multiviscosity oil with a rating of 10W-30 is a good all-around viscosity for mowers. The 10W refers to the oil’s flow at low temperatures, while the 30 refers to high-temperature viscosity.
Lawn mower engines do not require synthetic oil, but you can use it for potentially longer life. Make sure it still meets API SJ specs for small engines.
Avoid automotive oils without the proper classifications – they lack the additive packages that mower engines need.
Checking Lawn Mower Oil Level
Regularly checking the oil level is important to prevent premature wear and engine damage.
Consult your owner’s manual for the proper procedure. Typically, the mower should be on a flat, level surface with the engine stopped and cooled down.
Remove the dipstick, wipe it clean, then reinsert fully and pull back out to check the level. It should be within the indicators on the dipstick – not too high or low.
Top up with new oil if required, but avoid overfilling past the full mark. Too much oil can cause smoking, oil leaks, and engine damage over time.
When to Change Lawn Mower Oil
Here are some general oil change guidelines for mower engines:
- Change oil after the first 5-10 hours of operation on a new engine to remove initial break-in contaminants.
- Change oil every 50 hours of runtime or once per year, whichever comes first.
- Change oil more frequently if operating under heavy use, hot conditions, or dusty environments.
- Always change oil if it becomes contaminated with water, dirt, or fuel.
The hour meter on your mower tracks total engine run time. But if your mower does not have an hour meter, you can estimate hours based on average mowing duration and frequency.
For example, mowing 1 hour per week for 20 weeks equals about 20 hours of annual runtime. In this case, you would want to change oil at least once per mowing season.
Signs Your Lawn Mower Needs an Oil Change
Aside from strictly following the time-based guidelines, watch for these signs it’s time to swap out the old oil:
- Discolored or black oil
- Gritty texture when rubbed between fingers
- Thin, watery consistency
- Gasoline smell
- Excessive smoke from the muffler
- Low oil level on the dipstick
- Knocking or rattling engine sounds
How to Change Lawn Mower Oil
Here is a quick overview of the oil change process, though be sure to consult your mower’s owner’s manual for specific instructions:
- Run the engine for a few minutes to warm up the oil so it drains smoothly.
- Disconnect the spark plug wire.
- Clean the area around the oil drain plug.
- Place a shallow pan under the drain hole.
- Remove the drain plug and allow oil to drain completely.
- Replace the drain plug when finished.
- Carefully pour in new oil up to the full mark on the dipstick.
- Dispose of old oil properly – never dump down drains or on the ground.
- Reconnect the spark plug wire when finished.
Be sure to use new oil with the proper viscosity and classification as previously discussed. Refer to your mower’s owner’s manual for the correct oil type and capacity.
Proper Used Oil Disposal
Because motor oil contains toxic chemicals and additives, it’s important to dispose of it safely after changes:
- Recycling center – Many auto parts stores and local recycling centers accept used oil.
- Hazardous waste collection – Check with your municipal waste department for used oil drop-off events or sites.
- Service center – Some auto repair shops will take your old oil.
- Never dump in the trash – Oil dumped in landfills can contaminate soil and water tables.
- Never pour down drains/sewers – Oil residues can pollute waterways and poison ecosystems.
Make sure used oil is transported in sealed containers labeled as “used motor oil.” This helps prevent spills and proper disposal at the recycling facility.
FAQs about Lawn Mower Oil Changes
Does oil go bad if left in a lawn mower?
Yes, oil will eventually degrade and oxidize if left in a mower engine between uses. It’s best to change oil at least once per mowing season to clear out contaminants. Letting old oil sit too long in a hot engine can lead to increased build-up and sludge.
What happens if you overfill oil in a lawn mower?
Too much oil can cause smoking, oil leaks, spark plug fouling, and decreased engine performance. Always use the dipstick to fill to the proper level. Overfilling may also cause oil to enter the air filter and combustion chamber.
Do lawn mowers need special oil?
Yes, standard automotive oils are not ideal. Look for oil that meets API service class SJ or higher for small air-cooled engines. Avoid automotive oils without this designation.
Can you mix different types of mower oil?
It’s generally not recommended. Different oils may not be compatible in terms of additives, viscosity, and detergent levels. Stick with one oil brand and viscosity grade for best performance and to prevent complications.
How do you dispose of old lawn mower oil?
Never dump oil or pour it down drains. Take it to an oil recycling center or hazardous waste collection site. Some service centers may also accept old oil. Be sure to transport it in a sealed, properly labeled container.
Conclusion
With proper oil change intervals and quality oil, you can keep your lawn mower engine running smoothly for years to come. For most mowers, aim to change oil at least once per mowing season or every 50 operating hours.
Store oil correctly, check levels regularly, and watch for signs of degradation if you have doubts about its age and condition. And be sure to dispose of old oil in an environmentally responsible manner.
Following a diligent mower oil change schedule will pay off with a healthy engine and reliable start with each use. Your mower will be ready to tackle the yard for many mowing seasons down the road.
