Because the oem’s are bound by the epa and that’s all they CAN recommend. Many here have seen the carnage left behind with bearings going bad prematurely. On top of that, small 2 strokes continue to make more power down to about 24:1 due to added ring seal.
Another reason is that most new saws today use strato technology and are about 30% more efficient due to it. That 30% more efficiency equates to 30% less oil running through the lower end to lubricate the bearings. 50:1 in a strato saw is very similar to running 70:1 in a traditional 2 stroke. Another way to look at that is 50:1 in a traditional two stroke (as far as how much oil the bearings see) is very similar to running 32:1 in a strato.
The 50:1 craze got started 40 years ago largely because richer ratios were fouling plugs and creating carbon that would build up. There are many new oils out today though with enough detergent in them that they don’t build carbon at all and have proven to actually burn cleaner yet at heavier ratios because of the detergent. If you use a good oil that does not promote carbon, (Motul 710 is perfect), there are no drawbacks to running extra oil.
