Industrial and agricultural replacement cycles are much, much longer especially in a depression. The guy who runs the stables just bought a truck that was ten years old to replace his previous horse mover. I have no idea how old any of his agricultural machinery is other than that it far more than ten years old.  You'll have easy access to diesel - what do they run machines off in the US - for much longer.

Replacement cycles in poorer areas are much longer as well.

Taking out cars is only 40% of oil use anyway. What model are you using to determine the knock-on effects of that?