What to do if you Accidentally Add Oil to the Fuel Tank

You’re refilling your fuel tank, when you realize you’ve just poured your two-cycle fuel-oil mixture in instead of regular gasoline. Or maybe you got distracted and accidentally began to add oil without looking where you were pouring. Or maybe a well-meaning significant other made a whoops. However it happened, you now have oil where it shouldn’t be. So what’s your next move?

If you didn’t try and crank the motor with oil in the tank:Fuel Tank

  1. Drain the Contaminated Fuel – If you can, remove the gas tank from the unit and dump all of the contaminated fuel out. There will still be some oil left over in the tank, so add in a tiny bit of clean fuel, swirl it around, and dump that as well. This should remove almost all of the oil from your tank. If you can’t remove the tank, you’ll want to tip the mower on its side and try and drain the fuel from the tank. You don’t want your engine to be tilted for two long, as it can cause oil to flow back out of the crankcase. This can cause lubrication issues at times.
  2. Refill the Tank with Clean Fuel – Don’t fill the tank, just add enough fuel to get the mower up and running for a bit.
  3. Prep the Carburetor – Don’t prime the engine in the usual manner. Instead, remove the air cleaner and add some fresh gasoline directly to the carburetor to ensure it is getting pure gasoline, without any oil particulates at all in it.
  4. Start the Mower – Just start the mower as usual, and see how it goes.

If you’ve already tried to crank the motor before you realized there was oil contamination, you’ll need to take some extra steps:

  1. Drain the Contaminated Fuel
  2. Drain the Fuel Lines and Carburetor – If you tried to start the engine it means it has moved the mixture of fuel and oil down through the fuel lines and into the carburetor. You’ll need to take the fuel system apart, drain it, and rinse as many parts as you can. If you primed the engine, you’ll also need to clean your primer out. You may even need to replace parts of the system.
  3. Clean the Carburetor – This is the most important step, as oil can gum up your carburetor, causing the fuel-air mix to be off, possibly rendering your mower inoperable. This could require a complete disassembly of the unit.
  4. Remove and Clean the Spark Plug – Oil gets everywhere, and the spark plug was trying to light the fuel with the oil in it, so it could still be wearing remnants. Pull the spark plug and clean off any contaminated fuel, and clean out the hole for the plug, then replace it.
  5. Refill the Tank with Clean Fuel
  6. Prep the Carburetor
  7. Start the Mower

If these steps do not fix your mower, you will need to schedule a service appointment with your mower mechanic, as it may need complex work done. Hopefully, it won’t come to that.

About AndrewT

Written by Andrew T for LawnEq - The specialists for Lawn Mower Parts and Small Engine Parts. We offer genuine premium OEM parts for Land Pride, Toro and many more dependable brands.