Hi, I am new here, just joined... I also have a Mark III, and this will be the 3rd season now. I burned stove coal in it, the very first year, and it burned good. I had klinkers, and some large chunks of ash, but not that bad. The 2nd year, I burned the same, but got it from a different place. Needless to say, it was bad coal. It had lots of shale in it, and I had problems with large rocks or unburned coal getting stuck in the grates. I had to keep an eye on the fire all the time, because I never knew when I would get a good hopper full, or a bad one. First year, I burned approx. 3 ton of stove, and it lasted the whole winter, and kept the house at 70 degrees. Last year, with the bad coal, I went through all but 5 ton that I got. I was hoping to have some left over, but that did not happen! I had about 1/3 rock in my ash, and had a hard time raking the grates. I did have some unburned coal, but not too bad. This year I decided to change to a smaller size coal. After all the Mark III can burn a few sizes of coal, not just the stove coal. I decided to get some PEA coal this year, and see if it will do better for me. I did not like fighting with the raking part of it, as I did this last year. It was still warm out, but I decided to fire up this new coal, the pea I just got. Got a good wood fire going, and started to fill up the hopper with the pea coal. I had some very small pieces fall into the ash pan, when I first loaded the hopper, but it was very, very little. Way less than I honestly expected. I got a good fire burning, and filled up the hopper. I think I set the screw (draft) at 2 1/2 turns. I work 3rd shift, and I come home in the middle of the night for lunch break. So, I cam home, and checked the fire. It was burning real good, and not in need of anything. I think I did turn the draft to 2 turns though... To make a long story short, I left the fire go out.... but it burned a good 14 to 15 hours on that one load. I had an even burn in the hopper, and the edges were totally burned as well. I think the smaller coal makes a difference. It will tend to burn the coal faster, at the front of the grate, by the screw draft, as that is where the air comes in. But I had a complete burn, with no, or very little waste. It was completely burned, and mostly ash in the ash pan, except for some unbrned coal, from when I raked the grates. I rake my grates gently, and until I see some red ash coming down into the ash pan. When I begin to get the red ash, then I stop raking. Hopefully this load of coal will do me good this year. I would say 50% of the problems people have, is getting bad coal, or the wrong size coal, then the other 50% comes from not regulating the air correctly, both draft, and flue, or damper control.. I have both an in pipe old fashioned type pipe control, as well as the automatic one, that has a weight on it that can be adjusted to fip open and closed.. I use the hand damper when burning wood, and the automatic, for coal. Like I said, I think this smaller coal burns way better than the stove coal, I have burned the past two years. As long as the coal does not fall through the grates, I think it burns more even than the stove coal. ANother thing, is to make sure that you have a high enough chimney, to get a good draft. Ok, thanks for your time..... When cold weather finally does hit, I will be sure to let you know how good this coal (pea) really does, after burning for a few days, or week.. See Ya!