We've had quite a few good posts about the TEOST 33C test and whether it's relevant. Star polymer VII, very high levels of moly, concentration of VI, AO and base oils all play a role.
ASTM D8447 - Turbo Charger Deposits by Thermo-Oxidation Engine Oil Simulation Test
ASTM D8447 - Turbo Charger Deposits by Thermo-Oxidation Engine Oil Simulation Test - Testing now available at Savant Labs.
www.savantlab.com
GM turbocharger test: No correlation for deposits with TEOST 33C or moly
It turns out that TEOST 33C test is useless for judging turbocharger protection. Antioxidant is the key, along with the VII (or the lack of it) and dispersant. Moly has no effect. However, I think TEOST 33C may be better correlated with intake-valve deposits (IVD) in turbo gasoline...
bobistheoilguy.com