Have you considered sheepskins? They surely beat cold vinyl or even leather on a cold morning. My wife uses an aftermarket seat and back pad that has both motors for massage as well as heaters in it. Great if you have a bad back and it is sold at Costco for about $35-40. Much cheaper than a new set of seats.

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'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles