I really did a lot of research on this as I have been know to loose sleep over such questions. This applies to US market as I don't know if this stuff is available in Europe/Asia:<P><BR>1. Best Gas: Chevron Supreme. 91-93 Octain. Reason, Techron, the only proven additive that keeps engines clean, very clean.<P>2. Best Air Filter. Toss up between K&N and Amsoil, both reusable and both high airflow.<P>3. Best Oil. Amsoil (specifically, Series 2000 0W-30). Very expensive, but so is a $40,000 wagon. Reason, ASTM tests done independant of any marketing hype, Amsoil is the best in most important charactoristics..... Kenetic Viscosity, Film Strength (3300 psi), Cold pour point, and Flash point. Also, if you want you can run it to 1yr/35,000 miles with out changing the oil (so long as you change the filter every 7500 miles) as the additives are very robust.<P>I personally stick to Volvo's 7500 just because I can justify the $8 per quart at that interval. My 97 960 which is now out of warrantee goes 6 months 15000K between oil change and a new filter every 3 months or 7500.<P>4. Oil Additive. None!<P>5. Gas Additive. Chevron Techron (only every 3000 miles) <P>6. Wax - many are good, as long as they are carnuba and I like Zymol and Mcguires (sp?).<P>7. Leather cleaner - Zymol. Reason, doesn't leave a film or make it shine like the cheap stuff.<P>Pardon my bad spelling and good luck.<P>Sam<BR>