Should You Use Ethanol-Free Gas in Your Lawn Mower?
In This Guide
Standing at the pump wondering which button to press for your mower is a fair question, because fuel choice is behind most small engine repairs. Choosing ethanol-free gas for your lawn mower, or at least the lowest ethanol blend you can find, is one of the simplest ways to avoid clogged carburetors and hard starting. Below we explain what ethanol does inside a small engine, when ethanol-free fuel is worth the extra cost, and what to run day to day.
What Ethanol Does Inside a Small Engine
Ethanol is alcohol blended into most pump gas. It works fine in cars, but it causes real trouble in small engines for two reasons. First, ethanol attracts moisture from the air. Over time the water and ethanol separate from the gas and settle at the bottom of the tank, a process called phase separation, which corrodes the fuel system and makes the engine hard to start.
Second, as the fuel ages the lighter parts evaporate and leave behind gummy deposits that harden into varnish, clogging the tiny passages in the carburetor. A mower carburetor jet is thinner than a pin, so even a trace of varnish chokes it off.
Which Ethanol Blends Are Safe?
| Fuel | Ethanol | Safe for mowers? |
|---|---|---|
| Ethanol-free (recreation or marine) | 0 percent | Best choice |
| Regular E10 | Up to 10 percent | Approved, use fresh |
| E15 | 15 percent | Not approved, can damage |
| E85 | Up to 85 percent | Never use |
When Ethanol-Free Gas Is Worth It
Ethanol-free gas costs a little more per gallon, but it pays for itself if your mower sits unused for long stretches. Its big advantage is shelf life and cleanliness.
- It stays fresh far longer. Ethanol-free fuel lasts around 60 to 90 days untreated, and longer with a stabilizer, while E10 starts to break down in about 30 days.
- No phase separation. With no ethanol, there is nothing for moisture to bond with, so no water settles in the tank.
- A cleaner carburetor. Less gumming means fewer clogged jets and easier starts after a layoff.
- Best for storage and occasional use. If your mower sits over winter, ethanol-free fuel dramatically reduces spring starting problems.
What to Use Day to Day
If you mow every week, fresh E10 from a busy station with a stabilizer added before winter is perfectly fine. Regular 87 octane is all a mower needs. Premium higher octane gas gives no benefit unless your manual specifically calls for it.
If you mow only now and then, or store the mower for months, ethanol-free fuel is the smarter long term choice. For the ultimate protection some owners use canned premixed fuel, which is ethanol-free and stays stable for years, though it costs much more per gallon.
The Simple Fuel Rules That Prevent Repairs
1. Keep it fresh
Use fuel within 30 days, or add a stabilizer the day you buy it.
2. Stay at E10 or below
Check the pump label and never use E15 or higher in a mower.
3. Stabilize for storage
If the mower will sit more than 30 days, treat the fuel or run the tank dry before storing.
4. Buy from busy stations
High volume pumps turn over their fuel faster, so the gas you get is fresher.
Already Have a Gummed Up Carburetor?
Switching to better fuel prevents future clogs, but it will not clear varnish that is already in the carburetor. If your mower is hard to start, surges, or dies after years of stale ethanol gas, the carburetor likely needs a cleaning first.
Wildwood cleans carburetors and services fuel systems at your home, then sets you up with the right fuel habits so it does not happen again. We quote a flat rate before any work begins.
Rather Have a Real Technician Handle It?
A Wildwood technician comes to your driveway, diagnoses the problem, and fixes it on the spot, usually in about an hour. More than 10,000 repairs completed since 2019, with flat rates quoted before we arrive so there are no surprises.