Not to forget that right now, FarmVille is offering the Fuel for Coins in the Market. You need to earn any Co-Op Farming medal this week. You can go for the Tomatillos (See my progress here) or any of the usual crop. But for that the normal crops are rather hard to achieve! So I would suggest you go for the Tomatillos!
Anyway back to my Free Fuel thing... There is the screen that shows that you can buy Fuel with FarmVille Coins if you actually progress to Level 20 and above.
The Fuel that can be paid off in coins...
So go and level up and then you can join the Co-Op Farming as well as get Fuel for your farm! But honestly I don't think this is a good deal. You are better off getting free fuel from your friend's Facebook Wall Feed!
Share and learn. Learn and share :)