Thanks for your interest in Berryman. “B-12 CHEMTOOL“ is a family of gasoline fuel additives and carburetor cleaner aerosols, and there are at least five different formulas (only one of which is a “C” product). The best pourable part #s for a piston soak are 0101, 0105, 0116, and 0121. That same particular formula is available in aerosol form as 0110, 0117, and 0120,

In addition, there is a "C" (VOC Compliant) product for the aerosol version, which is our part #0117C.

If you choose to work with an aerosol, yes, you can spray it directly into the combustion chambers. Just be cautious as it the spray is pretty forceful, and any B-12 CHEMTOOL product can ruin a paint job in short order.

Regardless of the B-12 CHEMTOOL product used, it should NOT be introduced into a hot engine. If it’s too hot to comfortably hold your hand on for any length of time, then it’s too hot to add to the engine.

If you’re doing the piston soak, I would not introduce the chemical into the combustion chambers if their temperature is over about 100-105°F (38-41°C). For using B-12 CHEMTOOL in the crankcase, you want the engine as cold as reasonably possible in order to prolong contact time. Doing the crankcase treatment first thing in the morning is the general recommendation.

To be clear, you would have better luck with one of the pourable products.  I believe you can order the 0116 from www.mscdirect.com to be shipped to Canada.