I had an duh moment when I finally realized what is seriously unfair about the tractor upgrades. Normally we get a quest and even if the task for that quest may originally be generated randomly (e.g. co-op orders) or based on your FV2 level, you know when you complete that task exactly what it is going to give you - advancement to the next stage in the quest, favors, rich order points, hearts - whatever.
These tractor upgrades are different.
First the card sets are randomly generated. I first tried grid size (failed by one card). Then I tried oil capacity (failed by one card). Thought I'd give oil capacity another look and this time the card set for the same upgrade is completely different.
Then the cards obtained by completing tasks are also randomly generated (though based on easy, medium, hard tasks turned in).
So EVERYTHING is random. An unlucky person (like me) may put in hours of work and come up one card short while a lucky person may get the upgrade with the same (or even less) amount of work. It just doesn't sit well with me to do so much work and have NOTHING but a few oil packs to show for it.