Can You Use Synthetic Oil in A Lawn Mower? Things You Should Know Before Doing So

As an avid gardener with over 15 years of experience maintaining my lawn and garden, I’ve tested my fair share of motor oils in my trusty lawn mower. Like any machine, a lawn mower needs the right lubrication to keep its engine running smoothly. And when it comes to oil, you have options like conventional oil or synthetic oil. But can you use synthetic oil in a lawn mower?

I’ll admit, when I first heard about using synthetic motor oil in small engines, I was skeptical. Synthetic oil has always been marketed for high performance vehicles and racing cars, not basic lawn mowers! But after doing more research and talking to my mechanically-inclined neighbor, I learned synthetic oil actually has some potential benefits for my Briggs & Stratton engine.

The key advantage is that synthetic oil simply performs better than conventional oil, particularly in hot running engines like lawn mower motors. Synthetic oil has a higher viscosity index so it maintains a more protective lubricating film at high temperatures. This reduces friction and engine wear. Synthetic oil also resists thinning out from fuel contamination and oil breakdown better over time.

However, there are also a few considerations to keep in mind before switching to synthetic, which I’ll discuss more throughout this article. But first, let’s take a deeper look at the pros and cons of using synthetic oil in your lawn mower’s engine.

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Advantages of Using Synthetic Oil in Lawn Mowers

After the introduction, let’s dive into the potential benefits of using synthetic oil in your lawn mower’s engine. I’ll break this down into the key advantages I’ve seen firsthand from my own experience experimenting with synthetic motor oils over the years.

Improved Lubrication

One of the main advantages of synthetic oil is it simply lubricates better than conventional oil. The base oils used in synthetic formulations have properties that allow the oil to flow easier when cold and maintain viscosity when hot.

This is critical for small engines like lawn mower motors which have to start and run across a wide temperature range. Synthetic oil has a higher viscosity index, so it will still flow adequately to coat and protect critical engine parts when the weather is freezing cold. But it won’t thin out as quickly as conventional oil when the engine gets hot and starts to put more stress on the oil film.

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Increased Resistance to Contaminants

Another benefit of synthetic oil is its increased resistance to contamination and breakdown. The tight molecular structure of synthetic oil does not shear or degrade as easily over time. This allows it to better withstand pollution from dust, dirt, fuel residues and other contaminants that find their way into the crankcase.

Conventional oil is more prone to viscosity loss and acid formation as the motor oil oxidizes and reacts with combustion byproducts. But quality synthetic oils using PAO or ester base stocks retain their viscosity, TOTAL Base Number, and antioxidants for longer oil life. Keeping engines cleaner with synthetic can reduce sludge formation and abrasive wear.

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Better High Temperature Performance

Synthetic oil is also designed to handle high engine temperatures better than conventional oil. The base oils in synthetic formulations have very high flash points and fire points, over 300°C in some cases. This reduces the risk of oil oxidation and viscosity breakdown when the engine gets hot, especially under heavy loads.

Synthetic oils resist vaporization and oil consumption at high temperatures as well. This protects against deposit formation and oil leaks over time. Conventional oil is more prone to volatility and boiling off once the engine gets extremely hot. Overall, synthetic oil protects better against heat stress and overheating damage.

In summary, synthetic oil can provide improved cold weather lubrication, better heat resistance, increased contaminant handling, and longer service life for lawn mower engines versus conventional motor oils. Let’s now look at a few of the potential drawbacks.

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Using Synthetic Oil in A Lawn Mower

Potential Drawbacks of Synthetic Oil

While synthetic oil has some clear lubrication advantages, there are also a few things to keep in mind when considering its use in your lawn mower:

Higher Cost

The most obvious issue with synthetic oil is its higher price tag. Synthetic oils typically cost 3 to 5 times more per quart than conventional motor oils. This can definitely drive up the cost of ownership and maintenance requirements.

More frequent oil changes are recommended for lawn mower engines, so that higher synthetic oil price gets compounded over time. Many conventional oil users simply can’t justify the added expense of running synthetic in basic mower engines.

Seal Compatibility Issues

Some older lawn mower engines may also have seal materials that are incompatible with synthetic oils. While modern engines feature seals designed for both conventional and synthetic oils, older designs only accounted for conventional oil use.

Switching to synthetic can potentially cause oil seepage and leaks in older engines. Softened gaskets and seals meant for conventional oil may shrink or harden when exposed to synthetic formulations. Evaluating engine condition and seal materials first is advised.

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Over-reliance on Additives

There is also some debate about whether synthetic oil quality overly relies on supplemental additives versus the inherent qualities of the base oil composition. Conventional oil refiners argue the base stock quality used in synthetic oils is not substantially better in itself.

While synthetics enable more durable additive packages, the true longevity gains stem mainly from those additives, not the synthesized hydrocarbon molecules themselves in that argument. The reliance on additives to achieve performance milestones raises questions for some about true synthetic oil quality.

In summary, the potential drawbacks primarily relate to higher costs, seal compatibility on older engines, and questions about the role of additives in synthetic oil performance. But overall, the improved protection and durability offered by synthetic oil still makes it an excellent lubricant choice assuming proper precautions and maintenance practices are followed.

Let’s now go over some best practices on how to use synthetic oil properly in lawn mower engines to maximize the benefits while avoiding any pitfalls.

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Best Practices for Using Synthetic Oil

When making the switch to synthetic oil in your lawn mower, there are a few important best practices to follow. Properly using synthetic oil will help maximize the benefits while avoiding potential issues.

Check Manufacturer Guidelines

The first step before using synthetic oil is verifying it is recommended for your specific engine. While most modern lawn mower engines can utilize synthetic oil, always check your owner’s manual to confirm compatibility.

Certain older Briggs & Stratton, Tecumseh, Honda and other small engine designs called for conventional oil when manufactured. Using synthetic in those engines can risk leaks or seal swelling. Consult your mower’s manual or check with the engine manufacturer directly if unsure.

Once you confirm synthetic oil is approved, follow the recommended viscosity grade and service intervals suggested. Using the manufacturer-recommended motor oil, whether synthetic or conventional, is always advisable.

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Assess Engine Condition

It’s also a good idea to thoroughly inspect your engine before switching oil types. Look for any pre-existing leaks, seal cracking, gasket deterioration or other signs of oil seepage. Repair any external leaks first to prevent oil loss or dripping problems after the swap.

Examine the condition of major seals like the crankshaft and camshaft seals. In moderate to older engines, these may be hardened and inflexible. The switch from conventional to synthetic could cause swelling or shrinkage, resulting in new oil leaks.

Replacing worn seals and gaskets beforehand reduces the risks when transitioning to synthetic oil. It also provides an opportunity to confirm all seals are modern materials designed for either conventional or synthetic oils.

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Change Oil Regularly

Once running synthetic oil, stick closely to the recommended change intervals. While synthetic oil has extended drain capabilities, lawn mower engines work hard and get contaminated quickly in dusty grass-cutting conditions.

Follow the oil change frequencies suggested in your owner’s manual, even if shorter than the maximum intervals typically advertised for synthetic oils. Avoid pushing past the recommended lawn mower engine oil change times.

When changing synthetic oil, be sure to use a high-quality synthetic of the identical viscosity grade and certification as required by the manufacturer. Mixing oils can negate the benefits of synthetic lubrication over time.

Here are a few other tips for getting the most from synthetic oil in lawn mower engines:

  • Let engine warm up before high loads to reduce oil thinning on cold starts
  • Clean air filters regularly to minimize dirt ingestion into oil
  • Use fuel stabilizers during storage to prevent fuel dilution of oil
  • Check oil level frequently and top-off when needed

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In summary, following manufacturer guidelines, assessing engine condition, changing oil regularly, and sound care practices will optimize the benefits of synthetic oil while avoiding potential drawbacks. Properly using synthetic oil enhances cold flow, hot temperature performance, wear protection, and engine cleanliness over the long run.

Synthetic oil can be a great upgrade for lawn mower engines. But like any machine, the proper use and maintenance principles still apply. Now that we’ve covered the key considerations for using synthetic oil, let’s recap the core takeaways on the debate.

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Now that we’ve explored the pros and cons of using synthetic oil in lawn mower engines, let’s recap the key takeaways from both perspectives.

On the advantage side, synthetic motor oil offers better all-around lubrication and protection versus conventional oil:

  • Improved viscosity across hot and cold temperature extremes
  • Increased resistance to viscosity loss from contamination
  • Enhanced thermal stability at high operating temperatures
  • Lower propensity for sludge buildup and engine deposits over time

However, there are some valid counterpoints to consider as well before relying solely on synthetic oil:

  • Higher initial purchase cost per quart of synthetic oil
  • Potential seal incompatibility in older small engines
  • Questions about the role of additives in synthetic formulations

My ultimate opinion after years of firsthand use is that synthetic oil is indeed a smart upgrade for most modern lawn mower engines. While the benefits are less pronounced compared to high performance car engines, synthetics can still enhance lubrication enough to justify the extra upfront price tag.

But proper precautions need to be taken, including:

  • Verifying synthetic oil is approved for the specific engine
  • Inspecting seals, gaskets and o-rings before switching
  • Following manufacturer oil change intervals closely

Assuming synthetic compatibility is confirmed and maintenance practices are followed, synthetic oil can be a great way to get a little extra protection and cleaning power out of your lawn mower engine.

The key is approaching synthetic oil as just one part of an overall engine care regimen. Practices like regular air filter cleaning, spark plug replacement, coolant flushes and proper storage are just as important for maximizing engine life and performance.

But combined with other best engine care practices, upgrading to a quality synthetic oil is generally a wise move for lawn mower engines. I hope this article gave you some helpful insights on both sides of the synthetic oil debate and how to leverage synthetics properly in your own mower! Let me know if you have any other lawn care tips you’d like to share in the comments.

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