Can't vouch for ZX1 Extralube but all additives are not a waste of money.
Car oils and petrols (like anything today) are made to a price - and manufacturers being what they are (ie not charities) will only put in the minimum they have to.
Molybdenum Disulphide is added to many high performance industrial lubricating oil and greases (and has been for a long, long time) - because it is a well proven (but expensive) compound that greatly decreases metal to metal contact. Molybdenum is one of the lowest friction materials known, the disulphide bit makes it stick to metal. The coating produced protects the bearings during starting at the time before the oil has reached them, and also protects at much high temperatures than oil can. Molyslip is the most common Molybdenum additive.
Petrol additives also work, but you get hardly any in supermarket petrol and plenty in V power or Ultimate petrol. They keep the fuel system and injectors clean and generally get rid of the varnish and gunk left behind by cheaper petrols - try a tank of high octane in your car every so often and feel the difference in performance - (and this effect last longer than the tank of petrol) - and then tell me that additives don't make a difference. At the end of the day it's all down to price.
