What is the correct fuel & oil mix ratio in a modern chainsaw?

Thursday, September 3, 2020

The engine set up of a chainsaw from 1959 might not recognised today's modern chainsaws. One of the main causes of this is better & more efficient uses of fuel and oils - so much so, the fuel mix ratio of fuel (gasoline) to oil has changed a great deal. 

Older saws have tended to have smaller ratios - often the recommendations were 40:1 but today's engines can take a 50-to-one ratio. 

For example, the Husqvarna 272 made in the 1980s had recommended mix of 40:1 and the Husqvarna 272 made in the more modern 2020 has recommended mix of 50:1

Woodchoppers ask the question about fuel mix ratios because they can affect the smooth operation of the saw. 

Running too much oil can cause excess carbon build-up which contributes to spark plug 'fouling'  - meaning the plug will not provide adequate voltage to the firing tip and that cylinder will not fire properly. 

The way a 2 cycle engine works, is that the oil in the fuel lubricates everything. While running a saw on less oil it most likely won’t cause a problem in the short term, it will however likely cause increased wear and shorten the overall life of the saw. 

Translation: use the correct ratio - which is what the manufacturer says to use. They know their own engines, If you do not know the ratio, look in the user manual - if you've lost it, a quick google for a PDF copy should sort you out. 

If you cannot figure out the ratio mix, a cautious person might decided to add a little bit of extra oil and have the presence of mind to regularly check the spark plug for carbon build up.
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