No love for muscle engines?
This little dude here was running at foot crank for most of its life, only recently got that electric engine. Despite weighting more than 2 tons, it is technically a tricycle (2 small wheels 11" + 1 wheel 13"), which allowed the foot crank to keep its acceleration at 2 km/h. Most of the tiles visible contain upgraded reinforced panels, storage batteries and filled cargo holders, because my playstyle involves hoarding vastly excessive amounts of crafting materials, food, ammo, CBM duplicates, books, drugs and weapons and then never using them.
Bike engines are safe when offroading and silent enough for cities, but can build up respectable (70km/h) speed in straight line. And best of all, I can use them without feeling guilty about wasting carefully hoarded resources.
I only wish that it was possible to use bike engine as backup for when main engine breaks/consumes all fuel and to attach alternators to bikes for renewable energy in the darkness (underground, in bad weather etc.).