On my 1990 300E 4matic there is a lever under the hood to disable the front drive of the 4matic system in order to service. Could I drive for long periods with this lever pulled? Would it harm anything? It would seem to me a smart thing to do when driving in summer, then in winter engage this and drive in all wheel drive. It would save gas, and wear and tear on the front drive system. Does this make any sense, or am I an idiot? I had a 99 4matic with no such lever?