CH₃CH(OH)COOH — the homebrew default, sold at 80–88 % w/w.
H₃PO₄ — sold at 10 %, 75 % and 85 % w/w. Triprotic.
C₆H₈O₇ — usually a solid (monohydrate). Triprotic.
CH₃COOH — vinegar at 5 %, glacial at 100 %.
HCl — "muriatic acid", 31–37 % w/w. Strong.
H₂SO₄ — battery acid at ~35 %. Strong in its first proton.
The acids the engine models.