Is there anyone could tell me about auto additives and care products, which brands are most popular and expensive?
Thank you so much.

Amsoil i think has the best synthetics as far as oil, transmission, and gear lubes. They also have a good fuel additive called P.I. BG offers some good products such as the BG44k. I also like Lucas' Transmission Stop Slip for trannys that are just getting a little loose. Hope that helps.