Can You Leave Gas In A Lawn Mower All Year Round?

When you're wrapping up your last mow of the season or stowing away lawn equipment that you only reach for occasionally, it can be easy to forget that gas has a habit of going bad over time. Most people associate this with winter storage — after all, that's usually when your machine is allowed to sit without use — but this should be taken into consideration during all seasons. Standard gas can only sit in your lawn mower for about 30 days before it starts to go bad, so it's safe to say that you should not leave the same gas in your machine year-round. Since high temperatures and humidity can also speed up the degradation process, the condition of your gas should stay top-of-mind during the summer.

With that being said, there are things that you can do to extend your gasoline's lifespan as it sits. Some fuel stabilizer manufacturers say that adding their products to your gas can keep it safe to use for up to three additional years, but that's a bit of a lofty claim. Gas that's in the tank of a lawn mower isn't stored in perfectly sealed container, so even with an added stabilizer, the absolute maximum lifespan you can expect is around a year – less if you're dealing with fluctuations in temperature. Without stabilizer, there might be a once-in-a-blue-moon situation where the same gasoline sitting in a mower's tank for an entire year won't cause problems, but you're almost universally going to end up with issues if you attempt this.

Let's say you fuel up your mower without adding a stabilizer and use the same gas indefinitely, season after season. For the first month or so, you won't run into any issues. After that, the gas is likely no longer usable for outdoor tasks, and you'll start to see the difference in your machine. At first, bad gas might make it difficult for your machine to start, cause sudden engine shutoffs, result in increased smoke, or cause overall poor performance. If you let it sit even longer, you'll have to face off against more serious, long-term damage to your carburetor thanks to the gunk that the degraded gas has left behind. Untreated gas sitting in a machine year-round will almost certainly start causing these bigger impacts, so draining your mower and adding fresh, stabilized gas periodically is incredibly important. Even with fuel stabilizer added from the jump, it's best to err on the side of caution and replace the gas well before the year is up.

While completely emptying your mower when you know you're going to be storing it away for a while sounds like the most responsible approach here, you actually have a few options. First, you can fill your mower's tank with fresh, stabilized fuel, and run it for a few minutes before putting it away to ensure the fuel gets through the whole system. Make sure to fill the tank to the top to reduce the chances of condensation forming in the machine and causing rust. Alternatively, you can simply empty the gas and run the engine until it's completely dry. Either way, whenever you are emptying old gas, make sure to drain the carburetor bowl to ensure that there's absolutely no gas left behind that will gunk things up.