Whether you’re running a classic motorcycle or a modern chainsaw; if it has a two-stroke engine you’ll want to use the best quality 2t oil, to ensure the engine runs well and doesn’t seize. That’s my RD250 above and I run it on the best quality two-stroke oil because I don’t want to be riding around worrying whether it will seize, I just want to enjoy myself on it!
Cheap two-stroke oil is a gamble at best but in reality, it’s a false economy.
With a poor quality oil, your engine won’t run as well, nor be properly lubricated, meaning it’s at a greater risk of seizing up. When it comes to motorcycles, power is important and so is throttle response. With a quality oil, you’ll know your engine is on-song and running crisply.
When it comes to saving money in the long-term, replacing the piston – or worse, rebuilding the engine – is far more expensive than spending a little extra on a quality oil.
When you’re talking about a few quid being the difference between cheap 2-stroke oil and a premium one, is it really worth trying to penny-pinch?
Table of Contents
Why do two-stroke bikes need oil mixed with petrol?
When comparing a two-stroke engine to a four-stroke, the most obvious difference is that in a two-stroke engine there are two complete revolutions for every combustion cycle, whereas, in a four-stroke, there are – you guessed it – four!
Unlike a 4-stroke, there is no engine oil in the crankcases of a 2-stroke engine and therefore the piston is not being lubricated by a pool of oil held in the bottom of the engine (the sump).
Therefore, for each cycle, a 2-stroke engine takes in the petrol it needs to burn and the oil it needs to lubricate the cylinder. This is known as premix or sometimes known as petroil.
On some motorcycles and garden machinery, you will add the two-stroke oil directly into the petrol tank at the correct ratio. This is often referred to as ‘premix’. On other motorcycles and – more commonly – scooters, you’ll have a two-stroke oil tank, where you pour in the neat two-stroke oil and it gets injected into the engine alongside the petrol. This is sometimes referred to as prelube.
What does two stroke oil do?
The two-stroke oil is used during the combustion process to lubricate the piston and cylinder bores. As there is no ‘engine oil’ contained within the crankcases – as is the case with a 4-stroke motorcycle – without two-stroke oil, a two-stroke engine will seize without oil.
This is due to the piston generating too much heat when moving up and down inside the barrel.
A quality two-stroke oil ensures the engine runs crisply and is capable of remaining well lubricated and cool, even when used hard.
The different types of 2-stroke oil
There are essentially four types of 2-stroke engine oil:
- Vegetable / castor
- Petroleum / Mineral
- Petroleum / mineral or semi-synthetic oil mixtures
- Full synthetic oil
Vegetable oil, or castor oil, are naturally derived vegetable-based oils used forever and a day. When mixed at high oil to fuel ratios e.g. 20:1 and even higher in petrol, these oils have good lubrication potential, but their inability to remain mixed is a less than desirable attribute. For fast revving engines such as karts and smaller capacity motorcycle engines, vegetable-based oils often have what is called ‘high cling volume.’ Because of the high volume of oil and its normal viscosity, it appears to bind at intense rpm (15,000 +) to the bearing and piston skirts fending centrifugal force effects and aiding in heat dispersion.
The downside is that if the carbon build-up that accumulates in the engine isn’t serviced (i.e. removed) regularly, it can be responsible for fouled spark plugs, excessive smoke, and combustion deposits which can result in engine damage.
The heavy use of oil will also reduce RPM, alter the octane level and burn levels of the fuel mixture due to commonly used shear volumes and with the additional benefit to increase the cost of the racers oil bill. The effects of over-oiling on engines with power valves when using this type of oil with the recommended oil / fuel ratios are not recommended.
These 2 stroke oils are extracted from natural reserves of mineral crude oil, which are then cleaned with various complex cleaning and filtration systems from different containments. Mineral oils of the base quality 2 stroke are typically obtained from crude oil of lesser quality which generally includes more difficult containments to extract. This is the region where 2 stroke oils start to vary from 4 stroke oils, Fuel blending additives along with other various additives to improve combustibility and lubricating properties are applied to the crude base line and can often be a derivative of reclaimed engine oils in low quality blends from different market places.
It is widely accepted that the standard is adequate to the intended intent. The low revving older trail, farm and early scooter engine style can run all day on these oils although there are generally worse emissions than more advanced 2-stroke oils.
The semi-synthetic oils are a blend of conventional synthetic developments combined with natural oils of greater consistency. In general, the balance of these oils is a bulk of mineral with a small amount of synthetic additives. The oil blender also comes with a cross section of synthetic additives. Many of these have their own specific identity and purpose enabling a more accurate blend of oil to produce the performance and emission requirements accompanied by affordability for the modern 2-stroke high-performance engine.
The improvement in mixing agents and additives to reduce oxidation, corrosion, separation of fuel / oil and cavitation by oil pumping makes these excellent lubricants for Endure, performance scooters and other 2-stroke motorcycles that tend to travel further between engine rebuilds
In the last 5 years or more, the new completely synthetic 2-stroke engine oil as it is widely called has come a long way. Newly engineered polymers, biodegradable inclusions, detergents and additives that have exceeded previous lubricating standards now have other recognisable characteristics, such as octane enhancement and stabilisation, gas generating compounds to further improve combustion providing almost smoke-free emissions. Quality burning and lubrication allows some production motorcycles to run 60:1 in fuel / oil ratios, even in high revving 60cc 2-stroke racing engines with long service intervals and no undue wear of internal engine parts.
Many of the successful trial bikes are running 100:1 and endure long days of stretching their backs, again with no unnecessary low-lubrication results.
Nevertheless, these additives are the minority in an oil blend made from ultra-high quality base crude oils that still make up the bulk of the oil volume. One hundred per cent synthetic does not mean that the oil in this bottle is made entirely in a science lad beacon. This is explained by the fact that many manufacturers sell 2 stroke oil blends with a percentage of castor oil for additional fastening to those long straights.
There is an abundance of oil option on the markets but one thing is for sure that the price of the upper end commodity has improved. The emission requirements from various countries are now a major player for the 2-stroke manufacturing industry as a hole, so the collaborations between engineering and oil science are pleasing to the construction of the modern 2-stroke engine and its high-performance engineering and inclusions.
There is a lot of opinion on the subject of oils & oil ratios so try to remember the engine dynamics of the conventional 2 stoke engine to human psyche and its often rejection of the reality of modern engineering and marketing when asking the question.
Best Two Stroke Oils by bike type
Different bikes benefit from running different two-stroke oils and also different fuel to oil ratios. Here we list the most common applications.
What’s the best two-stroke oil for classic motorcycles
This question is a little bit like the question of ‘what’s the best high street coffee chain?’. The answers are numerous, mainly based on opinion and can be debated until the cows come home. Then someone will come along and say none of them are any good and really throw a spanner in the works.
Some riders believe that a specifically labelled classic motorcycle two-stroke oil is the best option but the reality is that a better quality oil is the best bet for any engine, no matter how old it is.
Today’s cheap two-stroke oil is far better than the quality two-stroke oil of 30 years ago. Expensive two-stroke oil might be deemed unnecessary by some, mainly because vintage or classic motorcycles don’t rev to the same high rev ceilings as modern machines but if you can afford it, go for a quality brand like Castrol’s A747.
The best two-stroke oil for modern motorcycles
If you’re running a modern two-stroke then look for an oil with a JASO FA, JASO FB, JASO FC or JASO FD specification. This is a Japanese oil standard benchmark, with FA being the lower spec and FD being the higher spec. The higher the spec, the most costly the oil is likely to be.
For any modern two-stroke, it’s best to use a quality certified oil.
What’s the best two-stroke oil for a scooter?
While it’s tempting to put in the cheapest oil you can find, go for something designed for a scooter engine, to ensure it runs sweetly. A proper scooter two-stroke oil will also have a low-smoke output, which is ideal as you don’t want to be sat in a cloud of your own fumes while you’re buzzing around town.
Two good options are Silkolene’s Scoot Sport 2 and Castrol Power 1 Scooter 2T. They’re designed to keep your engine clean and running well, especially with lots of stop-start riding, which can clog up the engine and exhaust if you use a basic oil.
Best two-stroke oil for a trials bike
The best trials bike oil is another hotly debated topic in the forums. A lot of trials bikes are 2t because this makes them a lot lighter, so they’re easier to handle.
They also spend a lot of time going very slowly, with the engine revving quite hard, so a build-up of exhaust fumes and unburnt gunk form the engine is a topic some riders worry about.
Having trawled the various forums and owners groups, the general consensus is that any quality two-stroke oil is fine and that hardly any riders have known a trials bike to seize up, even ones ridden in anger.
However the main topic revolves around getting the mix ratio right. Too much and you’ll gum up the engine, too little and you risk engine damage.
Most road-going two-stroke motorcycles use a fuel to oil ratio of around 25:1 however with a trials bike you need far less 2t oil, so a mix of 60:1 to up 100:1 is common.
Recommended oil: Motul 800 Factory Line 2T
What’s the best-smelling two-stroke oil?
The smell of burnt two-stroke oil is subjective. Some people love it, others can’t get enough of it.
We trawled a few forums to get a good idea of what smells people rate when it comes to their oil and here’s are the ones we found most commonly mentioned
- Maxima 927
- Klotz Super Techniplate
- Ipone Strawberry
- Castrol A747
- Motul 800
Clean-burning two-stroke oil
If you want a clean-burning oil that’s smokeless, or at least low smoke, then try Motul 800 or Mobil 1 MX2T.
Having trawled through various threads on owner’s forums, the general consensus is that these two oils are the business. We also saw a few mentions of Honda’s HP2 oil but this is the same as Mobil’s MX2T.
All two-stroke oils create smoke and you have to remember that even the cleanest engine burn will emit some unburnt petrol and oil and some partially burnt, which is where the smoke comes from.
However, if you want minimal smoke, try to stick to fully synthetic over mineral oils. If you really can’t make up your mind, the two options above are a good bet.
Smokiest two-stroke oil
On the flip side, if you want to make as much smoke as possible (some riders of retro bikes like the RD350 like to recreate the hooligan scenes of their youth), then there isn’t a ‘high smoke’ oil but you could add in a higher concentration of oil into your tank.
You don’t want to go overboard but a slightly richer ratio should see more smoke from your exhausts.
Cheap two-stroke oil vs premium
It’s tempting to buy cheap two-stroke oil.
If you compare something like Halfords 2-stroke garden engine oil, which costs £6 a litre, to Silkolene Pro 2 which costs around £24 a litre, there’s a huge difference.
You could buy 4 litres of the Halfords cheap stuff to 1 litre of the Silkolene.
The trouble is, with a really cheap 2-stroke oil, especially one designed for garden machinery over motorcycles, is that you’ll almost certainly run into problems.
Firstly, you should never run your motorcycle on two-stroke oil that’s designed for a hedge strimmer or a chainsaw. It just won’t be able to keep up and a few miles down the road, your bike will seize.
We’ve read stories of RD250 owners putting a bit of Stihl 2-stroke oil (or similar) in their tank to get them home from work and seizing up before they made it home
However just because an expensive two-stroke oil is better, it doesn’t mean you have to run the most premium one you can find.
If you’re buying from Halfords, go for quality oil, not one for garden equipment. They have a regular 2-stroke oil, priced at £9 a litre or a fully synthetic, priced at around £12. You pay for convenience as these prices are close to the prices of the better brands but the fact is you can ride to a Halfords and pick it up the same day.
However if you’re going to mail order your oil, sticking to oil that’s more than £10 a litre should see you right. Oils like Motul 800, Castrol Power 1 Racing 2T and Silkolene Comp 2 Plus are excellent quality two-stroke oils with great owner feedback.
The problems associated with cheap two-stroke oil
You can get severe pre-ignition due to the build-up of carbon in the combustion chamber and on top of the piston. Preignition is a serious issue that will overheat the engine, and eventually melt.
I never witnessed this with carburettor jets gunging, but many people complain that their carburettor gets gunged up. It blocks jets, which eventually causes the engine to stop. This could also lead to a poor mixture, melting the piston too.
A clogged carbon exhaust may cause excessive back pressure inside the cylinder. This can blow out the base gasket and contribute to air leakage, resulting in a thin mixture and a piston being melted.
Cheap 2 stroke oils seem to have a higher flash point, which is why they’re not burning away at lower temperatures. And if you do a lot of enduro or trail riding where the bike can get a lot of spooge if not revving too hard during the difficult parts. This will collect in and stream out of your exhaust, and spray on your fender.
2-stroke engine oil FAQ
I’ve accidentally put 2-stroke oil in a 4-stroke engine
Two-cycle oil is intended to burn to lubricate the engine in the upper cylinder section. It is not meant to be in the crankcase. It probably would wreck your engine. Remove as much as possible by draining the oil. Then top up with 4 stroke oil, run for a few minutes to allow the two oils to mix, then drain the oil and replace it again with the correct 4-stroke engine oil. The 2 types of oil are not cross-compatible and shouldn’t be mixed.
You should not use 4-stroke engine oil in a 2-stroke engine and vice versa.
How do you mix two-stroke oil?
There are various methods you can use. Most people take a large petrol can, like a 5-litre, and then add in their two-stroke oil into the tank after they’ve added the petrol. Or if you want to be super accurate, you can buy a mixing bottle like this one which has been designed for garden machinery and powertools. You can mix each litre of fuel very accurately with the gauge markings on the side.
If your ratio is 25:1 that means 25 parts of petrol to every part of two-stroke oil. So for 1 litre of petrol you’ll add in 40ml of two-stroke oil.
What’s the best 2t oil for a Vespa?
A Vespa, like any other 2t scooter, needs a quality oil. Any JASO rated oil will be ideal and yes, it’ll be a little bit more expensive than the cheapest stuff but it will ensure your engine runs well.
You can also buy oils designed specifically for 2t-engined scooters, like the Putoline TT scooter which is suitable for premix or injection scooters.
Best for garden machinery
Two stroke oil for things like strimmers and chainsaws is usually of a lower standard than that used in motorcycles. So if you own a stroker but you also have some nifty two-stroke-engined garden equipment, then your motorcycle oil will be plenty good enough for your garden machinery.
Thanks to the following websites that helped us put this two-stroke oil guide together: