If you use a lava furnace fuel
do not see a reduction in fuel appearance .
Comments 5
How long did you wait ? The lava will last for 1000 seconds, compare http://www.minecraftwiki.net/wiki/Furnace
I've just got a perpetual furnace on 1.6.2
I used a hopper to feed 9, 9, 18, 64 different smeltable block types into a furnace. (Numbers approx, but /not/ multiples of 8 except for the final stack.)
The first 9 items were manually placed inside the oven, not in the hopper.
I set up a second hopper to extract the finished items to a chest. (This was done while stuff was smelting, in case that matters)
During the smelting I extracted some of the early items manually from the furnace, getting XPs for them, but I let the lower hopper do most of the work.
After loading up, I fueled the furnace with one block of coal. (80 items' worth of smelting)
After smelting 50 or so of the 90-ish items I'd set up, the fuel indicator in the furnace had yet to drop at all. It should have been below 50% by this stage.
Logging out and then in again, I now seem to have a perpetual furnace from one block of coal, if only I had enough raw materials to keep it fed. I wonder if you might be able to do the same with other fuel types (lava (should be easy), coal, charcoal, saplings( ! )), if you can just find the right tweak to the number of items loaded.
I know there's several permuations of actions there that might have had a bearing. I will add updates if I manage to narrow down the cause any further.
@Simons Mith: Your issue is MC-10025.
Unable to reproduce.