After using your lawn mower regularly, you get a pretty good idea of how much gasoline it uses to cut the lawn. So you’ll definitely notice if all of a sudden it starts to demand more gasoline. My lawn usually uses a fraction under a full tank to completely cut my lawn, so if I have to reach for extra fuel to finish, I know something is going on. If your lawn mower is suddenly using too much gas, it’s more than likely a symptom of a bigger problem, and finding the root cause should be at the top of your to-do list.
Why is My Mower Using So Much Gas? (The Short Answer)
Excessive fuel consumption can stem from a change in the cutting conditions, lack of servicing, and a defective component within the mower. The extra strain on the engine will cause increased fuel consumption, whereas defective parts and settings will unnecessarily overconsume fuel.
10 Possible Reasons for Your Mower’s Excessive Fuel Consumption
Step one is to understand if your lawn mower is truly using too much gas in the first place. Then step two is to pin down exactly why the mower is demanding more gas. So, let’s go through some of the common causes why your mower is suddenly burning through a lot of fuel.
Dull Blades
Having dull blades on your lawn mower will put the mower under additional strain and cause it to overwork. This extra power strain results in the engine working harder than it needs to and leads to it using more fuel. The best solution for this is to make sure your blades are always sharp. I also recommend that you make sure to sharpen the blades to the correct angle, even if you need to sharpen the blade without removing it.
Long or Wet Grass
You’re probably already well aware of how much more effort it takes both you and the mower to cut a lawn that has been left to grow for an extra week or two. If you’ve ever tried mowing wet grass, you’re also familiar with this extra strain.
This is why I suggest sticking to a regular cutting schedule and avoiding wet mowing conditions. Both of these will dramatically increase your lawn mower’s fuel efficiency while helping out your wallet and physical energy. Additionally, you’ll have a much better cut, healthier lawn and no issues with clumping grass.
Wrong Octane Gasoline
Knowing what octane fuel to use in your lawn mower is key from both the engine’s perspective and fuel consumption. Low octane fuels burn faster than high octanes, and are therefore consumed more quickly. So if you unknowingly switched to a lower octane fuel, you’ll be sucking a lot more gas compared to the higher octane options.
The recommended fuel for small engines is 87 octane, but it’s best to always check what fuel specification you should be using for your specific mower and follow the manufacturer’s recommendations.
Quality of Oils
The oil that sits in the sump of your lawn mower engine is primarily used to lubricate the engine and reduces the friction of moving parts. Low octane oil or cheap oil is not able to efficiently lubricate and therefore causes the engine to work much harder than it needs to. This extra effort results in your lawn mower using too much gas. Therefore, make sure that you inspect your oil regularly and have a high-quality oil on hand.
Fresh Fuel
Bad fuel in your lawn mower will most definitely reduce your engine’s fuel efficiency. Carry out a visual inspection of the gas in the mower’s tank and remove the fuel if you discover it has gone bad.
Fouled Spark Plug
A fouled spark plug does not have the ability to burn gas efficiently and will end up spitting fuel out through the exhaust. The easiest solution for this is to swap out the plug for a new one. If you want to be sure it’s the spark plug, you can test it with an inline spark plug and check the plug’s ignition ability.
Dirty Air Filters
A dirty air filter is going to disrupt the air-fuel ratio and cause the engine to consume an increased volume of fuel. The best thing, in this case, is to pull out the air filter and give it a good cleaning or replace the filter. (Check here if you want to know how to clean a lawn mower air filter.)
Carburetor Mixture
Making sure that your carburetor is set to the correct air-fuel mixture is vital. These are the settings that tell the carburetor how much fuel it should be using. There are various places where this can be adjusted, from the idler adjustment screw to the jet adjustment. Grab the mower’s manual and find the correct adjustments for your mower, then make your adjustment.
Broken Carburetor Float
The float in the carburetor is the device that regulates the flow of fuel into the engine. Having bad fuel or allowing dirt to pass through the fuel filter will cause the float to get stuck or gum up. If the float can’t adjust automatically, it will cause extra unregulated fuel to pass through, and the lawn mower will use too much gas. The best solution here is to open up the bad carburetor and see what’s going on.
Valve Settings
The valve in the engine works in conjunction with the pistons to regulate the intake, compression, power, and exhaust strokes. In turn, these strokes regulate the air-fuel input, fuel compression, fuel ignition, and exhaust discharge within the cylinder. This is what makes up the fundamental process of a combustion engine. If the valves are not set correctly, then the process is not able to operate efficiently and will result in your lawn mower using too much gas.
As complicated as all of this sounds, the adjustment is actually very simple. Using a feeler gauge to set the rocker arm and valve will restore the engine strokes, improve your lawn mower’s performance, and increase fuel efficiency.
Yeah, none of those will make that much of a difference.
Hey Emily,
I’d agree that any of the reasons mentioned in the article separately may not make a huge difference, but when you start to add them together, you could begin to see the effects.
Usually, lawn mowers have small engines, so noticing excessive fuel use is difficult at the best of times, and most people wouldn’t notice. But, I will say that in my experience, I have noticed these individual issues can be more noticeable with zero-turn mowers with larger engines on larger areas. So, I would agree with your statement, “much of a difference.”
Thanks for your comment.
Cheers, Tom.