RE: DL50 what oil ratio?
After seeing what a few hundred gallons of Amsoil at 88:1 does to a DA100....... I'd never use the stuff.
My friend has a DA100 with serial number 160. It's OLD and has been run on Amsoil at 88:1 for it's entire life. He is the third owner, so no telling how many gallons of fuel have been run through the engine. I think it's safe to say several hundred at least. I know he's personally run at least 50 gallons through it.
It was low on power, so he called DA to ask about a rebuild. They told him between $400 - $500 for new cylinders, pistons, rings and seals. He is self-employed and not working much lately, so he couldn't afford the $$$ to have DA rebuild it. He asked DA if a new set of rings might freshen it up. They said it wouldn't hurt, but don't expect miracles. For $13 it was worth a shot.
We took the cowl off and removed the cylinders. There was BLACK HARD CARBON deposits on top of BOTH pistons. It was like 60 grit sand paper and would NOT wipe off easily. It was hard like a diamond. I picked at it just for a few seconds with an exacto knife to see how thick it was and how hard. I didn't want to damage the piston, so I spent minimal effort trying to scrape off a tiny piece of carbon. It was hard as a rock and probably a few thousandths thick.
Both rings were stuck in the ring grooves. The ring grooves had hard black carbon too. We cleaned the ring grooves a little after removing the rings. The right side ring was stuck so bad I had to break it to get it out. It was LOCKED UP in the ring groove from carbon deposits. It's no wonder the engine was low on power.
We inspected the cylinders. Hard carbon deposits on the top of the combustion chamber. No big surprise after seeing the pistons.
Installed the new rings. Use a little 3-n-1 oil for reassembly.
We then ran 2 gallons of fuel through it with my preferred oil. Husqvarna XP at 32:1 for break in. This is a half synthetic and half mineral oil product. The plane was flown doing the 2009 Sportsman sequences for those 2 gallons. During that time, it's belched out a lot of black spots and also a lot of chunks of carbon deposits.
First few tanks, the performance was mediocre, but thats to be expected. At the end of 2 gallons, the power is back to where it was before we messed with it. I tried talking him into running the same oil (Husqvarna) at 40:1 after the break in - thinking that since it's obviously already started cleaning the engine, it should continue to do so. Getting some of that carbon out would be good for the engine IMO. But he wants to switch to Red Line or Bel Ray or Penzoil.
I expect power to improve over the next 10 or 15 gallons. I don't care what brand of oil he uses. It's his engine. I'm just happy he finally saw the light about Amsoil and decided to quit using the stuff.
Some pictures: