Sir, I don't mean to challenge your experience and since I'm new to Vitz so I'll just seek further clarification. Do u think that an engine as new as Vitz 2013 ( even if it's 50-100k driven) will have oil residue clogged around VVTI cam n oil galleries? Secondly, when we decide to use the best available engine oils available in market, Why do we still need additives? Is a good oil not optimally formulated to take care of the engine, especially when one of it's main functions is engine cleaning? Thank you