The book tells me that the ratio is 20:1 but that is WAY to rich, I mix my gas 28:1,if you mix it 40:1 you will blow up your moter propley right when you trun it on.
Actually,28:1 is a richer mixture than 20:1.....Air doesn't mix with oil,so when your fuel atomizes, the more oil you have in it,the more molecules of air per molecule of fuel you will have since the air has togo somewhere....The less oil you have in a mix,the more molecules of fuel you have to divide the air molecules between which gives a richer mixture.....
I use and have used Amsoil at 40:1 with no problems in 4 years now...You will NOT blow your engine unless you use weed eater oil or some other cheap lube......
Hoodlum