Good luck with the new ride....
I get 36 MPG with My 99 all day long. Im quickly approaching 350000 miles.
So far .....
3 sets of tires, 1 brake job, 1 set of glow plugs, 2 "sets" of plastic fuel lines upgraded with Viton "o" rings and of course the dreaded evaporator core along with a new compressor and dryer. All in all I have good things to say about my car.
I change the oil every 10000 w/Mobil 1 5w-40 Turbo Diesel truck.In addition I change my Fuel filter every 20000 and fill it with Lubro-Molly before I screw it on.
My i recommend changing the rubber hoses. The supply line and the return. These hoses degrade and contaminate the fuel system. Then run two cans of Lubro -Molly through the system. Back on the fire wall on the drivers side is where you will find the 2 hoses. Grab an old coffee can fill it with L-M. get 2 pieces of 1/4 copper tubing about 10 " long. bend a 90 at one end, clamp both rubber lines to each copper tube it and dip it in the can. Run two cans through the system. Get a third can change the fuel filter fill it with L-M then road test it .....
Just my 2 cents
Happy Motoring
Anthony

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2003 SLK 230 (85000)
1999 E300 Turbo Diesel (388,000)
1991 350SD Turbo Diesel (185,000)