There are so many shades of gray here. I do few "highway miles" but I'm also not doing stop and go city miles either. I'm gently cruising at 35-50 mph on back roads with little stop and go besides the occasional stop light or stop sign. Are those city or highway miles as far as wear and tear on the engine? I'd argue they should count towards "highway miles" even though I rarely go on the highway. How many stops before it counts towards city miles? What about my friends who commute into Boston every day? They are on the highway and usually in constant stop and go traffic for 20-30 miles and 1-1.5 hours? Perhaps, but the other 20-30 miles of their commute are "easy" highway miles cruising at 70mph and on the weekend they are driving the gentle backroads in town. When I think "severe" I think of NYC cabs or Police cruisers that are starting and stopping constantly and when they aren't they are sitting there idling or work trucks that are constantly loaded and/or towing. I'd argue "most" people outside of major cities who do not use their vehicles for work or who do a lot of heavy towing or idling do not fall into the "severe conditions" OCI.
Originally Posted by ejes
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...