2 stroke oil in a 4 stroke motorcycle

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I’ve been running 2 stroke oil for a few years in my 4 stroke bike now,

And here are my findings:

  • It reduces friction in the upper cylinder, which is the main source of engine wear and heat.
  • Reduces engine braking by a minimal amount,
    The engine runs cooler.

With the right dose, you can notice:

  • an engine hp increase, from bottom to top revs, and in most cases, higher top speed.
  • MPG goes up.
  • Engine revs smoother, with less vibrations.
  • It restores a bit of compression loss on the piston rings and valves, thus higher torque.
  • Gasoline doesn’t get bad as fast
  • An easy way to increase octane levels of fuel by 1 or 2 (eg: 87 to 89), resulting in a lower chance of pinging


  • It makes gasoline a bit more expensive
  • Too much oil causes performance loss (as oil doesn’t combust as well as gasoline),
  • Minor plug fouling (usually below 50:1 ratios)
  • Minor carbon buildup (usually below 50:1 ratios)
  • And possibly harder cold starts when valves have buildup.

I’ve ran many different doses, and found the sweet spot for 4 strokes to be between 100:1 (smooth, easy riding), to 160:1 (performance increase still noticeable but less).

At 50:1, the fuel/oil mix is meant to lubricate both the top, as the back of a 2 stroke engine’s piston; since 2stroke engines don’t have an engine oil reservoir.

At 50:1, there is sufficient oil to form a buildup, and pass by the piston rings, lubricating the crankshaft and other mechanics inside the motor, as well as the valves, without really fouling the plugs.
For this reason, most 2stroke motors today, recommend to start with a mix of 32:1 for the first tank (white or blu-ish exhaust smoke visible), and switch to 50:1 for consequent tanks.

On a 4 stroke, only valves and the top of the piston need lubricating, not the engine’s internals.
Because of that, less oil is needed, and a lower dose can be chosen.
I’ve done tests ranging from 75:1 to 300:1, and found that:

  • 75:1 had a performance loss and low plug fouling
  • 100:1 gives nice lubrication, and recommendable for older engines with lots of miles.
  • 125:1 Sweet spot on performance and lubrication
  • 160:1 still good performance and low lubrication
  • 200:1 it is hard to distinguish between an engine without or with the mixture by ‘feel’.
  • 300:1 No noticeable improvement, engine acts like regular fuel.

Mobil is known for adding a small amount of oil into their fuels, while BP is known to add a proprietary chemical in their premium blends, that increases performance, many believed to be nitrogen based. Shell also uses a similar ‘performance enhancement’ blend, but in a less aggressive measure.

At 128:1, quite an easy number for us Americans, you’d have to pour 1oz in a 1 gal tank, or 3oz in a CBR300’s tank. This would be very close to the optimum dose, I’d say.
A small bottle of 6oz would last you 2 tanks and costs anywhere from $2.5 to $5.
A 5 quart 2stroke oil jar would cost you $25 to $30, resulting in $1 per 5-6oz, or, an additional of $0.5 per tank on oil.

  • At $2 per gallon, the overhead cost would be 1/12th, or 8%.
  • At $3 per gallon, the overhead cost would be 1/18th, or 5%.

The money really gets won back in MPG, as on average, the bike would have a 5% to 8% better fuel economy, OR, a ~5-8% better performance, depending on how you use it.
(Top speed can go up by 1 to 5%, depending from bike to bike, and fuel/oil mixture).

Most of all, piston rings and cylinder walls last longer, due to a cooler running engine, that’s more lubricated.

This video, is of an engine using a cleaning agent to, aside from cleaning, explains on upper cylinder lubrication..
Unfortunately the cleaning agent costs a good 4x more than 2 stroke oil, but 2 stroke oil doesn’t have the same engine cleaning capabilities.


EDIT: After tests, I have found that adding 2 stroke works on any engine, but is not recommended for Fuel injection bikes.
Bikes that rely on the O2 sensor to give data back to the ECU, will experience O2 sensor fouling; plus misreads due to a different chemical exhaust gas composition.

Another con is that whatever oil is inserted, robs the bike from the fuel it needs.
125:1 on oil in the gas, means 0.8% of fuel missing from the mixture, and a lean burn.
A carburetor is more flexible to this, but a fuel injection system is less. Especially when the bike already is running lean!


5 thoughts on “2 stroke oil in a 4 stroke motorcycle

  1. I actually made a video about this…
    Yes, lots of improvements in feel.

    FakeEmail btw here so i cant reply but wanted to comment.

    I use 500:1 not sure if ok to go 200:1 on EFi bikes.


    1. It shouldn’t be any problem.
      2 stroke oil is slightly heavier, but with a 1:128 (1oz per gallon) the ratio is well below 1% of difference.
      I experienced a difference on my bike between 300:1 and 100:1.
      Any lower dose, didn’t do much to the performance, and any higher dose would give more smoke in the exhaust.
      I ran it for a while on 100:1 and see some more carbon in the exhaust, but not much.
      While 1oz per gallon was the perfect ratio for me, I think 200:1 will work just fine for fuel injected systems.
      With a 200:1 dose, you probably will need to clean the cylinders by adding some seafoam in the gasoline every 10k miles or so.


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