Hey guys. I got a new Stihl line trimmer (weed eater) yesterday, and got a 6 pack of their Stihl HP Ultra synthetic oil with it. Mixed with a gallon of gas, it makes a 50:1 ratio. I was wondering if the this fuel mix would be ok to use on my older Mcculloch trimmer which requires a 40:1 mix. I know this new mix has less actual oil, but wasnt sure if it being a synthetic made it far superior, and ok to use.. What are your thoughts on this guys?