2 stroke oil

We recently bought a new Stihl petrol strimmer and the salesman was insistent that we not use 2 stroke oil, only the special oil made for the strimmer. We bought a 4 pack which should last us about a decade.

As mentioned, it was something about the special formulation for the newer strimmers. And I'm not willing to lose my new warranty to muck about with cheap 2 stroke for my motorbike.