The TEOST 33C test simulates the effect of engine operating conditions on the oxidation and deposit-forming tendencies of engine oils, especially in the high temperature Turbocharger area. The TEOST MHT® test simulates similar effects and conditions found in the ring belt and piston ring areas of the engine.

Oil samples treated with catalysts are pumped over a heated 33C Depositor Rod or a coiled MHT Depositor Rod on which deposits form. The weight of the Depositor Rod after the test is subtracted from its pre-test weight and added to the particulate weight collected by filtering the oil remaining. The results are reported in milligrams.