Is there any difference between left hand side fuel tank and seat tank and wonder if both tanks have same gallon or not? I would like to hear your feedbacks. Thanks 
Farmerd5

I researched the D4 OMI manuals in our ACMOC library and found the seat tank holds 30 U.S. gallons. The OMIs for the models with the side tank did not list the fuel capacity. I was able to find the capacity of the side tank in the ACMOC library D4 sales brochure, 25 U.S. gallons. 
Craig

What was the advantage of a side tank.My dad had a D2 with direct start and a seat tank.A neighbor had a D2 with a side tank and a starting engine.Another neighbor had a D4 with a side tank and direct start.Prefered driving my dads D2 over the other two because of the seat tank.By the way, these were all used for farming orchard trees in the 60s.

I have often wondered the same thing. My D47U has the side tank on the left and battery and hydraulic on the right so it is unhandy getting into the seat.

  Locally some liked the fender seat as they could drop the seat down in between the fenders so the bottom of the seat is sitting on the transmission housing and get a few more inches of clearance in some of the orchard’s. This tractor spent all of its life in an apricot, prune and cherry orchard in Santa Clara. It had some limb risers on it when I got it so it was like climbing into a midget race car. I through all of that away and went looking for a seat tank as that’s what we ran in our walnut orchard and was a much better in my opinion, and what I learned on. Now I am kinda wishing I would have saved that piece of history after it was explained to me by one of his neighbors…. But at the time in 1990 something I had a different vision. Then the other thought is some people need the fender tank so they can see the drawbar, After you run a D8k SA or D7G SA and have to hook up to a drag disc or ripper a person wouldn’t have much trouble hooking up with a D4 with a seat tank.