When I ran a woodgas setup, my oil changes were 3,000 mile intervals.
If you want to run an engine on woodgas, you must properly calculate the air injection nozzle sizes, how many, what diameter the reaction chamber should be, and how thick of a grate/what material to use for the estimated temperature of the charcoal.
The reactor should be burning hot enough to flash off any excess of tar and soot. In its optimal state, a gasifier can even produce a nearly clear gas, needing very little filtering. Unfortunately, control tests rarely apply to the real world when things like ambient temperature, air density, and moisture are accounted for.
Next, you MUST filter the gas. I prefer running it through a cyclone filter to remove heavy particulates and tars. After the cyclone, the gas passes through two radiators which will ideally cool the gas down to ambient aur temperature. This process will condense a lot of vapor, so you must plan to put a catch can at the lower end of the radiator which will need to be emptied every so often.
Finally, the gas will pass through a fine particulate filter. I like running a barrel full of sawdust which can be changed out whenever it gets filthy. Sawdust is cheap. You can use anything that is good at filtering solids.
Then pipe the cleaned gas to the intake. Run a splitter so the engine can use either gasoline or woodgas in case you ever have trouble with getting the fire right.
You will lose a good chunk of power with woodgas. Much like propane, you must check and clean the carbon buildup off of the valves. Expect to run at higher RPMs too. The faster you run the gas through the reactor, the hotter it burns and the better and output you'll receive.
forum.driveonwood.com
