When it comes to 2-stroke oil, it is highly recommended to use good quality oil from the likes of Stihl or Husqvarna. Using low quality 2-stroke oil can cause damage to your machine which can be very costly to repair.
Why Use High Quality 2-Stroke Oil?
Older machines use to dump half of the fuel mix straight into the exhaust, machines now dump around 10% of fuel making them much more cost effective to run and much better for the environment.
Older machines use to deal with the dirty fuel in the exhaust; this would then build up within the exhaust and also blow out into the atmosphere. The exhaust could be de-coked (cleaned) to clear away any build up allowing you to continue to use the machine with little expense.
In newer machines the dirty fuel is dealt with in the engine, which can stick onto the piston cylinder and can also get into the piston ring. The piston ring will stop moving in and out due to this coking which will cause scoring to the piston meaning your machine will not run. This damage can be very costly to repair, usually making the machine beyond economical repair (BER) which is not covered under the manufacturing warranty.
What Happens if I Don't Use Enough 2-Stroke Oil
The 2-stroke oil within the 2-stroke mix acts like a protective film. If you do not use enough or any 2-stroke oil it will cause wear on the piston cylinder walls as there is not enough / no lubrication for it to run as smooth as it should. 2-stroke oil is not compressible so it creates a film between the piston ring and the wall to stop them touching. If there is not enough / no 2-stroke oil there is nothing stopping bits of the piston ring touching the piston wall which will cause scoring (much like a barcode effect seen in the image below). This again is very costly to repair usually making the machine BER.
Stihl 2-Stroke Oil
The Stihl HP oil has more ash content than the super and ultra, this ash causes carbon which then chokes up the engine and causes scoring of the piston.
The best practise is to use the Stihl Ultra 2-stroke engine oil as this is the cleanest of all the Stihl oils. This oil has been designed to improve the performance of your 2-stroke engine over a period of time whereas using other oils will see a slight decline in performance over a set period. Lab tests have proved that with constant use of the Ultra oil, a piston which has been running for several hundred hours will still look almost new. This Ultra oil is 80% biodegradable and particularly low in sulphur (sulphur is the gasses given off) is much better for the environment.
The image above shows the wear on a piston cylinder when using different quality 2-stroke oils. The top line shows the wear on a piston of a DIY trimmer being used for over 50 hours with the different quality of 2-stroke oils (Stihl HP Ultra being the best sloping down to the Stihl HP). The second line of images shows a professional leaf blower using different quality 2-stroke oils after over 500 hours of use. As you can see the piston fares much better when using a high quality oil to ensure your machine has a longer working life. The bottom 2 images show the damage caused to a piston when using cheap quality 2-stroke oil from your local hardware store. This oil will cause damage to your machine much quicker which can effectively make your machine last much less time.
A few extra pence on the right oil could save ££ in repairs and maintenance.