I've had one of these for awhile, and it seems to do a pretty good job. My question concerns the mixture of oil to gas. it requires a 25:1 mix. my question is, why? During a tune up I used the canned Truefuel in it, and it ran just fine. My trimmer is used at full throttle quite a bit of time on the same fuel. Why is the oil mix so rich on he auger?