I've not seen the figures below disputed.
Len Deighton ‘Blitzkreig’
The shortage of motor vehicles was not unconnected with the great variety of vehicles being manufactured during the 1930’. By 1938 there were 100 different types of commercial trucks in Army service, 52 types of cars, and 150 different types of motorcycles. A drastic scheme – the Schell-Programme- had reduced this chaos, but still the German motorised columns looked like a parade of used cars and the supply of new vehicles was no more than trickle.
At the outbreak of war in 1939 the German armed forces resorted to the desperate measure of commandeering civilian motors. They took some 16,000, but these were swallowed up immediately to replace worn out vehicles, bring Army units to their full allotments, equip new divisions, and for training. None of the civilian trucks could be kept as a form of reserve, so there was no reserve. Civilian vehicles were flimsy by military standards, with only two-wheel drive, a far cry from the six-wheel (4four-wheel drive) Krupp trucks that were the army’s preferred equipment.
By February 1940 the situation was getting worse by the day. The Polish campaign, with its fighting, dust, and very bad roads, had caused some units to write off 50 per cent of their trucks. Replacements from the factories (many of those with only two-wheel drive and unsuited to combat conditions) were pitifully inadequate.
The army’s normal peacetime loss of trucks through wear and tear was about 2,400 trucks each quarter year, but only 1,000 new vehicles were arriving each quarter. In other words, the army’s supply of trucks was dwindling at the rate of 1,400 trucks each quarter year without fighting.