Our W124 wagon is off, but not a consistent (or linear) amount..... Always low, but anywhere from ~ 20*F to 50*F (was fun seeing -28*F last winter in CT).

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1961 220b: first project car - sold.
2000 CLK 430: first modern Benz - sold.
2001 CLK 55: OMG the torque!!! - sold
1972 280SE 4.5: Baby Gustav
1991 300TE 4Matic: Gretel the Snow Bunny - sold
1978 300SD: Katz the Free Man - given away
1980 Redhead: Darling Wife