For a 2T engine, it's just a necessity on the front side. For 4T, and those doing that 1oz / 5 gal, it's pretty much homeopathic levels. The more you add, the more directionally the user's going to be teasing deposits. Tcw3 formulations can vary a lot in performance depending upon the market they're catering to, so some are better at resisting deposition. All of that usage in a 4T engine is still under the assumption that supplemental lubricity is needed, but it really isn't with E10 because it is already additized. E85, perhaps, but I wouldn't want the mineral oil portions that come with cheap tcw3 formulas--for all prior deposit reasons.