Considering condition, mileage and service history are equal. a 420/560SEL are about half the price of the same SDL.

You can buy a lot of fuel for that money, for what amounts to a 5mpg-7mpg difference.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200