I can see 3000 mile intervals on cars that putz around town,because every car as far as I know that came with a little book in the glove compartment is being driven under severe operating conditions. At least that's what it says in the little books.People always look for low mileage cars, but I personnally won't buy a car that mostly hung around town unless I can get it for cheap.Every time you take off from a stop, the burning gasses have to slip around the top ring,get behind it, and push as hard as possible to force it to seal against the cylinder wall. That's where the wear comes from. Once you get 3600 lbs moving you could cruise on 2 cylinders. Also once you lock up an automatic trans, you are just moving fluid around. Around town friction material is being asked to do its job everytime the tranny shifts.Brake bands are applied and released hundreds of times. We all know what happens to an aluminum can when you bend it back and forth enough times.At any rate I change the oil at the recommended 5000 mile interval on the one car I may never get rid of; my 83 300TDT. I'm getting ready to do the 315,000 mile scheduled service,and the car fires up on cold winter morns and has plenty of power. In my opinion products like DELO (diesel engine lubricating oil) are necessary on over the road tractors because of the incredible loads they are subjected to;
I've used plain old car oil for years in all my diesels, but then again my cars usually never go less than 25 miles once they are started.I also have a double ended quick disconnect key chain with 2 keys for the wagon.It sets in the driveway next to the 560 because the garage is filled with a 67 230SL and a 71 3.5 280SEC which are both used to storestuff on. Getting back to the 300TDT, I fire it up about 10 minutes before my wife goes to work,leave the key in the ignition and lock the car with the other one. she drives off with car at operating temp. I think this adds to the longevity.

Peter

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