Recommended max number of polygons?

In a vehicle, how many polygons can you have until it starts lagging in BeamNG?

 

Now that depends on the amount of polygons in the rest of the map and other vehicles...

 

Stock vehicles are around the 100000 mark. Barstow I think is 85000 without wheels but including all engines/hoods etc. Might not be exactly what info you were after, but should be a decent ballpark if you were thinking of modelling. Pigeon has less of course, t series alot more.