Though they won't admit it (some don't even understand it), the vast majority of people qualify for the "severe conditions" driving OCI's. As such, I do 5k OCI's on all my vehicles. I don't trust the generic car computer algorithms, etc. To me "mostly highway" is at least 51%. Personally, if I'm being honest with myself, I never come close to 51% highway, and anything less than that is severe duty. To each his own however...