Exactly, due to emissions requirement, very few if any new mowers are 2 stokes. One of the problems is that the pre-mixed oil must be enough for worst case engine loading, which results in too much oil 90% of the time. Two-stroke outboard motors and snowmobiles have gone to variable ratio oiling, where the oil is carried in a separate tank and metered into the engine based on rpm and throttle position. This is too expensive for a lawnmower. If there is a 2 stroke mower on the shelf, it should say something on one of the warning labels (if they're not mssing) about needing oil mixed into the gas. A 4-stroke will usually have a prominent place to add oil to the crankcase with a warning label to add oil before starting the engine.