I am sure most of us have been there at one time or another, you realise your mower is almost out of oil and your lawn is in dire need of a cut.
You look around your shed and you suddenly realize you don’t have any suitable oil.
Then a thought springs to mind…
Can you put vegetable oil in a lawn mower?
Well, let’s find out…
Can You Put Vegetable Oil In A Lawn Mower?
No, you should never put vegetable oil in a lawn mower. It will not be able to withstand the high temperature of a combustion engine and will turn to sludge and gum up your engine. This will cause the engine to overheat and the result will be permanent damage. Vegetable oil is for cooking not for lawn mowers!
Don’t Even Think About It!
If you are considering vegetable oil as an emergency motor oil substitute, the answer is pretty much a definitive no!
There are a few issues, but the main one is that vegetable oil (or any cooking oil), has great lubrication properties… once!
But very quickly, it will not be able to deal with the temperature of a combustion engine as it has a very low boiling point.
It will rapidly accumulate viscosity and very quickly turn to foam/gunk/sludge and then equally as quickly gum up the parts of your engine.
The result will be your engine will quickly overheat and most likely be damaged irreparably.
You have to remember that vegetable oil is made for cooking, and it will start to break down when it reaches cooking or frying temperatures.
Engine oil on the other hand can withstand temperatures of up to 200°, then cool down, then heat back up, then cool down, then heat back up, etc, etc.
Vegetable oil cannot do this, neither can it lubricate, protect, cool and clean the engine.
What is more, there isn’t much price difference between vegetable oil and cheap motor oil.
The difference is, if you use vegetable oil you will almost certainly be left with the cost of replacing your lawn mower or if you are lucky, just a big repair bill.
I cannot ever see there being such a lawn-mowing emergency that you would need to risk putting vegetable oil in your mower!
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Motor Oil vs Vegetable Oil: Similarities and Differences
We’ve already established a few major differences between the standard motor oil used in many engines and vegetable oil.
To understand why it would be such a bad idea to put vegetable oil in your lawn mower, I thought it might be useful to look at the two substances in a bit more detail.
Motor oil is made from mineral oil. Mineral oil in turn is refined from petroleum that is found beneath the earth’s surface.
Vegetable oil, and other similar oils, are made up of the fatty acids produced by plants.
The most basic difference is that vegetable oil is a food ingredient used for cooking and is edible. Motor oil mostly definitely isn’t, and is toxic to humans if ingested.
Motor oils also contain additives designed to protect, cool and effectively lubricate engines. Vegetable oil doesn’t not.
On the contrary, as we previously discussed, vegetable oils are largely unstable and will oxidize and turn gummy and sticky when heated.
The only real similarities the two substances share is they are both viscous, insoluble in water and have a slippery or sticky kind of feeling.
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But I’ve Heard of People Using Vegetable Oil in Vehicles, Surely It Is Ok?
As we all attempt to find greener solutions and alternative fuels to help the environment, I am sure you no doubt have seen occasional stories of people using some kind of cooking oil in their engines, be that a car or a lawn mower.
It is possible to use vegetable oil in modern diesel engines (not petrol ones), but in pretty much every instance the car/lawn mower/vehicle has been modified.
Usually, this is through the installation of a heat exchanger to preheat the oil and reduce its viscosity.
There is also a process called transesterification, which turns cooking oil into efficient and functioning biodiesel.
However, this is something that needs to be done by an expert, not by you in your kitchen with a test tube and a few chemicals!
I’ve even read a few accounts of people with much older diesel engines using vegetable oil in them, but it certainly isn’t something I would risk.
There is an interesting case study from the Oberlin College Green EDGE Fund, that details how they converted a lawn mower to run on vegetable oil.
The total cost of the project for the one mower was $1,750, but it shows it can be done.
So What is a Good Emergency Oil Substitute?
The standard answer to this is that there isn’t one, and you should only ever use the manufacturer’s recommended oil.
And that generally is pretty true, it is recommended for a reason.
You are always best off using SAE-graded engine oil, as there are no replacement oils for engine oil, except engine oil!
You would want to look for something with the right viscosity and formulation. So if you were using a 10W20 you could use any brand, whether it be regularly, partially synthetic or fully synthetic oil.
If you have no 2-cycle engine oil, you could use 4-stroke oil as a one-off if you absolutely have to. It has a higher flash point, so will be less likely to cause engine damage.
Used regularly though it will cause build-up and deposits in your engine.
The thing about 2-cycle oil is it has special ingredients that reduce piston scuffing and wear on the walls of the cylinders. Four-stroke oil and motor oil doesn’t have this.
Used motor oil might work at a pinch as well, but it won’t burn as cleanly and will leave carbon deposits.
But really you need to think about how much of an emergency it is to use a non-recommended oil in any engine that could easily cost you in the long run.
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Final Thoughts
The risks of putting vegetable oil in a lawn mower far outweigh the benefits (actually there aren’t any benefits), so it most definitely isn’t worth it.
I cannot think of one situation where you would be so desperate to mow your lawn that you would need to even consider using vegetable oil as an emergency oil substitute!
Doing so will gum up your engine and cause it to overheat and be damaged permanently.
Remember the two substances are so different.
Engine oil is made to withstand very high temperatures and clean, cool and lubricate a very complicated piece of machinery.
Cooking oil… isn’t! It is meant for cooking.
Don’t put vegetable oil in a lawn mower, end of story!