Can I add two stroke oil to a 4 stroke lawnmower?

Is it safe to add two stroke oil to a 4 stroke engine?

So I recently bought a brand new lawnmower. It had a Briggs and Stratton engine which was a real selling point.

As I was in the store, I grabbed some oil as I figured the oil sump was probably empty.

Turns out I was right, as there was a big yellow warning sticker on the engine to remind the user to add oil.

To actually add 4 stroke oil.

 

That made me take note as I had bought only 2 stroke oil as that's what I had been adding to my old Briggs and Stratton engine until the casing gave way due to rust and I could no longer safely push the mower (see this picture).

So Maybe that wasn't the smartest idea in the world!

Given it was a brand new engine, what should I do? Use the recommended oil of course!

But I am not a smart man, Jenny. 

I wasn't going to drive all the way back to the store to grab the oil as that would have taken an hour and I really wanted to cut the lawn iwth my new mower, so I'd thought I'd just grab some 4 stroke oil from the petrol station down the road.

They had none.

Nor did the other one across the road.

Nor did the supermarket.

So screw it I thought and added the two stroke to the brand new engine.

And you know what happened?

Nothing but the grass was cut.

The engine didn't smoke and it started the first time which is simply a great feeling when you've just laid out some serious cash for your first ever brand new lawnmower!

Cool story bro but your example doesn't mean much...

Two-stroke engines and four-stroke engines operate on distinct principles, and understanding their differences requires a bit of technical insight.

In a two-stroke engine, the combustion and exhaust cycle is completed in just two strokes of the piston. This means that both the intake and exhaust functions occur simultaneously, allowing the engine to complete a full cycle every two strokes. This results in more power output for its size, as the engine can fire once every revolution of the crankshaft.

In contrast, a four-stroke engine completes its cycle in four strokes of the piston: intake, compression, power, and exhaust. The engine fires once every two revolutions of the crankshaft, which is why four-stroke engines are generally more fuel-efficient and produce less pollution compared to two-stroke engines.

The key difference between the two engine types is the lubrication system. 

In a four-stroke engine, the oil is stored in a sump system, which is separate from the fuel. The oil lubricates the moving parts of the engine, and the fuel remains pure for combustion. In a two-stroke engine, the oil is mixed directly with the fuel, providing lubrication as the fuel is burned.

Adding two-stroke oil to a four-stroke engine is not a viable long-term solution.

Two-stroke oil is designed to burn along with the fuel, and its composition includes additives that are necessary for the high temperatures and pressures in two-stroke systems. These additives are not suitable for the separate lubrication system in four-stroke engines. 

Additionally, the presence of oil in the combustion process of a four-stroke engine can lead to excessive smoke, carbon buildup, and long-term engine damage.

It's for this reason that you should indeed follow the engine manufacturer's advice and use 4 stroke oil in a 4 stroke engine.

Sure, the 2 stroke works in a pinch, but for the long-term efficiency and performance, the 4 stroke oil (SAE 30W) is the way to go.

If you suddenly feel you need to buy some 4 stroke oil, check out some options on Amazon.

engine maintenace, four stoke, lawnmower maintenance, oil, two stroke