The Lucas additive works the same way. I've been using it for more than 150,000 miles without any issues.


2002 X5 3.0 359,000 miles
2014 428i 63,000 miles


2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles


1970 Firebird under restoration

Yes, this is my understanding too. I used AT-205 recently on another car where it was worth a try before tearing things apart to replace the leaking seals. That was the first time I have ever used a stop-leak thing on a car of mine.

Key factor for me in doing that was convincing myself that there was little downside to trying it in case it failed. No conclusion yet on my personal trial here, but it seems to have improved things.

The AT-205 is a clear, low viscosity liquid. Looks almost like water. The 8 oz bottle treats about 6 quarts - of virtually any fluid other than brake fluid.

Key point is that it works by softening the seals, to hopefully allow them to bend, comply, and tightly seal to stop the leak.

That's different than most stop leak things, which work by causing the rubber in the seals to swell up a little, filling the gaps that way. For example, my understanding is that the "high mileage" motor oils contain additives that do this swelling.

BTW, are there any other types of stop leak things? This one softens seals. Others swell seals. Anything else?

I know some coolant leak stuff actually contains particles that are supposed to get stuck as they are leaking out of the small cracks or whatever, and mechanically plug the leaks by doing that. But I've never heard of something like that for oil.

Cure -all in a can/bottle = lots of pain with little results.

All BMW engines need to be resealed approx every 100,000 MILES Cost of ownership.