So, if one owns a classic car and just takes it out for occasional Sunday drives, and to & from the car show, he/she should change the oil every 3 months and other fluids (i.e. brake, coolant) every two years? What exactly do car collectors do to care for their cars properly besides constantly polishing them?

And for a car that is driven infrequently, is there any benefit to using a synthetic oil like Mobil 1 or Amsoil if it's changed out every 3 months? Because...it seems very expensive to do this. Should the oil filter also be changed every 3 months in this instance?

Likewise, it would seem from this discussion that it would be wiser to buy an older car that has higher mileage that was regularly driven on the highway rather than a low mileage car that was only taken out on Sundays for short trips.

When buying a used car, what kinds of things would one look for (besides service records) of poor oil change frequency or a lot of short distance driving? Or is there no way to tell without tearing down the engine?

I know it is much better for any car to run hours at a time on the highway, but as I live & work in the city and the freeways around here are often stop & go, I'm guilty of a lot of short trips...and I know my Mercedes runs a lot smoother after I've taken at least a half hour drive on the highway. I try to combine errands when I can, but there's still a lot of turning on/turning off the engine with at least 15 minute cooling off periods in between....is that also a bad thing? I'd feel weird to leave it idling for more than about two minutes. Maybe I should have bought an electric car instead of a diesel.

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1976 240D "Katja"