Some info here:
http://www.petrolprices.com/total.html
and at
www.Total.co.uk but nothing too specific .... here's the best info from a press release dated April 2005:
The benefits of TOTAL EXCELLIUM
1. The exclusive additives contained within TOTAL EXCELLIUM lower fuel consumption by reducing mechanical friction therefore improving the efficiency of a vehicles engine.
2. TOTAL EXCELLIUM fuels reduces CO2 emissions by up to 5% and cut pollution from Carbon Monoxide and black smoke by up to 25% in cars over 5 years old.
3. The new detergent contained in TOTAL EXCELLIUM cleans the most sensitive parts in modern engines, in particular the areas involved with petrol injection and high pressure diesel injection. In addition
TOTAL EXCELLIUM diesel has a higher Cetane Index improving its combustion properties from a cold start, resulting in up to 37% reduction in noise.