Diesel. Back in the day when diesels were one hell of a niche. Also, according to my copy of the '93 ADAC Auto Special, the BX was not actually as comfortable overall as one may think. In overall comfort (so, less "suspension" and more "what would you prefer to go cross-country in) it was beat by cars like the Ford Sierra or Mercedes W201, and on par with the Hyundai Sonata. The only worse midsizers were the Peugeot 405, Saab 900, Subaru Legacy, Renault 21 and Alfa Romeo 155.