FWIW I was a line technician at a large Toyota Dealership during the "sludge-monster" service campaign, During this I dealt with dozens of V6's with some of the worst sludge build up I have ever seen with my own eyes. On many of the engines affected Toyota would have us install a new short block and clean-up the sludged heads and reseal and reinstall. None of the 5 or 6 cleaning methods recommended by Toyota worked well but we found a local auto parts supplier that would sell us big drums of B-12 Chemtool that were big enough to dunk the entire head in and leave overnight. This was the ONLY 100% effective way that we found to clean this sluge off. Excellent chemical when used as intended.

I use B12 in my small engines to clean out the carb. I am rehabbing a neglected Tecumseh float carb for my old Ariens snowblower. I stripped down the carb and put the pieces in a cleaned out glass jar with a lid. I added enough of my 2 stroke mix to cover. I shook the jar several times and quit for the day. Today, I re-assembled the carb using a spray can of house brand carb cleaner. There was a 1/2 inch of sludge on the bottom of the jar. I contemplated soaking the carb in B12, but the can was 1/2 full and I didnt feel like driving to get more.

So, what's the update on this? This was BEFORE the bardahl fiasco, right?

I had low compression on a car I has rehabbing and tried a piston soak using 7 parts MMO to 1 part B12. Didn't solve my compression problem (worn rings), but when I had those same pistons out to replace the rings, the piston ring lands and rings were absolutely spotless. If there was any varnish or coking before the soak (not totally sure if there was) the MMO/B12 soak got rid of it.

B12 is great! I pour a can in my gas tank after every oil change to clean the injectors.

In my opinion, B12 and Berkebile Gum Cutter are the best cleaners.

my Buick dealership recommended this for my car. says its a great fuel system cleaner!!

It is the most effective air intake cleaner I have ever used.

B-12 Chemtool is outstanding stuff. I use it for gas engines and it keeps them running great. My other use for it is as a base for "Ed's Red" gun cleaner, 1/2 B-12 and 1/2 ATF. Be aware, it's virtually all solvents, so wear nitrile gloves and have gooood ventilation.