Low Quality Pistons

You craft these because a car is sitting by the road with gaps in its engine and you want to drive it home tonight. An engine does not run without pistons; in the game's own words they “convert expanding combustion gases into the motion that turns a crankshaft”. No pistons, no motion.

The low tier is the one you can make on day one. A Level 1 workbench and 25 metal fragments per piston is pocket change, and the blueprint costs only 15 scrap to research. An engine takes more than one piston, so count the empty slots before you craft. The small engine in a cockpit with engine wants fewer than the big engine module.

So when is low enough? For a two-seater that shuttles you from the beach to your base and then sits parked, it is fine. The weak spot is wear. With 60 durability they give out sooner than the higher tiers, and a worn-out engine part is how a car dies halfway across the map.