Use fresh gasoline with an octane of >89, use premium 2 cycle oil and mix it at 50:1 and you'll be just fine.

If 40:1 makes you feel better then do it but it's not really necessary if you're using quality oil.

It's critical enough to actually measure it. Just dumping some oil in a can and mixing it is asking for trouble. Get a measuring cup and a quality synthetic oil and mix it properly. Like davefr said, 50:1 with a high quality oil is fine.

FWIW and YMMV, I use an oil meeting JASO-FD and ISO-EGD specs. Echo and Husqvarna Low Smoke oils meet this spec & you can get the Husqvarna oil at Sears or Lowes.

From Echo's website:
Echo Power Blend Universal 2-Stroke Oil can be used in all of our 2-cycle air-cooled equipment ever made. You may also use this oil in any other brand of 2-cycle air cooled equipment, but it should always be mixed at the 50:1 ratio whether or not it was a 32:1 or 16:1 etc. machine. This oil is the highest quality 2-cycle oil on the market today. There is no need to have more than 1 tank of fuel for your 2-cycle equipment any more.

I'm not so fussy. I use what ever mix oil is readily available. I mix at 32:1 and use it in all my 2 strokes. The only 1 it smokes in is the old Lawnboy which specs 32:1. My old Stihl Farmboss specs 40:1 but has run fine on 32:1 for 30 yrs. I keep expecting to have to clean up the exhaust ports, but havent needed to yet.

Uncle sam has been requiring small 2 stroke engines to reduce emissions so most manufacturers now use 50 to 1 ratios because they emit less emissions. Check your owners manual and mix it according to the instructions. You saw might need more lubrication than the 50 to 1 ratio.

I would mix at 40:1 50 parts of gas is too lean ............what happens when your engine seizes up?Or refuses to start because there's not enough compression...will the oil manufacture's pay the repair bill? I doubt it...........

My STIHL BR600 backpack blower with the 4-Mix engine calls for a 50:1 oil mix. I have been using closer to 40:1, thinking more oil is better. After about 150 hours using only the STIHL Ultra full synthetic oil, I removed the spark plug and the valve cover to check the valve clearance. There was more carbon build-up on the spark plug than I expected to see. I also found lots of oil around the rocker arms, telling me it is getting more than enough lubrication at the 40:1 mix. Based on what I saw, I will probably go with the recommended 50:1 mix, with the Ultra oil. It should reduce carbon buildup in the combustion chamber. STIHL says their Ultra synthetic oil leaves very little carbon compared to conventional or blended oils. Charles Ranheim

I did a lot of asking and reading already. It is critical not to put excess oil if you have the hybrid 4 cycle engine like Stihl 4mix and Shindaiwa C4. They have valves that is very sensitive to oil deposits. It is troublesome to decarbon on these type of engines also. The gas mix go through the crankcase so you have to be careful what you are doing. Spraying water into the carb is out of the question and using too much Sea Foam regularly is not too good for the engine either. So only way is to either dissamble the engine or using Stihl decarbon solution which is corrosive. So keep the oil close to 50:1.

If you are not comfortable with 50:1, you better off getting a true 2 cycle engine. They are not as critical and also they are much easier to disamble to clean. Usually just remove carb, muffler and 4 bolts of the cylinder, you can access the piston to clean.

I mix mine to 45:1 or 50:1 for my C4 blower, use the same mix for my echo Hedge trimmer but put a few more drops of oil into the tank after adding the gas for good luck!!!

I regret buying the Shindi C4 blower and I would not get the Stihl 4Mix stuff mainly because of the extra maintenance. I have a Honda Trimmer which is 4 cycle with separate gas and oil. No oil in gas to form extra deposit, only from burning gas. Decarbon is lot easier, water or seafoam into the carb, then change oil, DONE!!!