I've often heard critics of alternative fuels complain that those who experience problems along the journey rarely return to admit their difficulties.

Well, here I am. I have had problems and I'd like to tell you about them.

I got an '84 F-350, 6.9 IDI, a few months back. This is a documented Navistar rebuilt engine with just over 20,000 miles on it since the rebuild (that's the main reason I found this truck so attractive). The previous owner told me that a while back he had experienced some smoking and power loss, so he replaced the return lines and tees and the problem went away.

I had been running my '83 Mercedes 300SD on a mix of about 50/50 centrifuged (20+ passes with a 120 GPH pressure-driven centrifuge from PA Biodiesel Supply) waste motor oil, which was a mixture of various weights, some ATF, maybe some other stuff too. No idea whether the oil was all non-synthetic or some of it was synthetic. The Mercedes had been running on this mix for months without any major problems, just smoking when cold -- but that's pretty typical for an old Benz, even on pump diesel.

So, confident I had a fuel that worked, I put it in my truck. And it worked well for a few weeks.

But one day when I was driving home from work, the truck lost power and started smoking. I pulled over and the engine died. I restarted the engine and things were back to normal. It concerned me, but didn't happen again the next day.

Then the same thing started happening more frequently. It got to the point where I couldn't run the engine for more than five minutes without it losing power suddenly, smoking like crazy, and dying as soon as I put the clutch in. Restarting it made things return to normal, for a few minutes, until it would happen again.

I went through a good amount of troubleshooting (see the thread for the details), and ultimately I came to the conclusion that it was my homemade fuel causing the problem. Switching the truck back to clean pump diesel makes the problems completely go away.

So, I don't know. Maybe there was something in the oil my engine didn't like (synthetic oil, perhaps). I don't think I've done any damage to my engine, but of course without taking things apart I couldn't say for sure.

Just a cautionary tale. From what I've heard, it's probably best to know exactly what is in your oil and avoid any synthetics. I thought I had centrifuged mine sufficiently, but perhaps not.

I'm getting out of the game, since I have to move to a house where I'm not allowed to have any of the equipment. All that stuff has gone to a friend of mine, so I'll try to report back occasionally with his progress.