Easy to fix, just put a Mercedes badge and a 240D badge on the back, they'll think the
smoking is perfectly normal.
From the Wiki page on the 1970's Mercedes Benz 240D:
It was at the time the fastest diesel engine available, though its 4-cylinder, 2.4 liter engine only produced 65 hp (48 kW). Along with a 3300 lb (1,500 kg) weight, performance today is considered extremely poor. Acceleration was negligible, and top speeds hardly exceeded 160 km/h (~100 mph).