The Correct Fuel Mixture Ratio

All two stroke engine will use a 50 to 1 ratio using today's two stroke oils.  I once used an old chainsaw probably from the 1960s, that had a sticker on it that said to use a 25 to 1 fuel/oil ratio, but that would have been using two stroke oils of the time period the chainsaw was manufactured.  In that chainsaw I used 50 to 1 ratio with no problems.  Today's two stroke oils compared to yesteryears are more efficient at lubricating.  It is like comparing today's synthetic motor oil to motor oils of decades ago.  All the equipment I use in landscaping, anything from a weed eater, leaf blower, chainsaw, hedge trimmer, use 50 to 1 ratio, and I use all types of makes and models, Stihl, Homelite, Husqvarna, Shindaiwa, and Echo, Sears.  I mix up a 5 liter fuel can and use it in all of the equipment for my customers and for my landscaping.  To calculate the ratio is simple.  For instance , if you have 1 gallon of fuel it is best to break it down into smaller units, like ounces.  One gallon = 128 oz.  You then divide this amount by the ratio of the mixture which is 50 to 1 (50 parts fuel, 1 part oil).  So therefore 128 oz of divided by 50 = 2.56 oz (you would just measure out 2.5 oz ) of two stroke oil.  If using metric,  say a 5L gas can, you would break this down to smaller units, which would be milliliters.  5L = 5000 ml.  5000 ml of fuel divided by 50 = 100 ml of two stoke oil. 

Some people think that is the fuel/oil ratio is wrong the engine will run rough or not start, this is false.  If you don't have enough two stroke oil you will just seize the engine (time for a new engine), a customer once forgot to put two stroke oil into the fuel then used it in a Shindaiwa weed eater, it lasted about two minutes and the engine seized.  And if you use too much oil your engine will just blow a lot of blue smoke out of the exhaust and gum up the muffler with a thick gummy like oil.  You won't damage the engine using too much oil, but it sure stinks and have blue smoke blowing everywhere.  Below is a chart of the different fuel to oil mix ratios.

Also see Step by Step Two Stoke Carburetor Rebuild, Two Stroke Engine Troubleshooting, Carburetor Troubleshooting Chart.

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