Eventually diesel will become more expensive and petrol less (supply & demand), the more company cars would be petrol. The real consequence is goods transported by HGVs would cost more.
Clearly nobody knows for sure, I reckon Foci, that sounds right
I can't see many company cars becoming petrol now, they just work off c02, and diesels are always going to be lower.
http://forums.focaljet.com/team-pit-stop/454703-how-pronounce-spell-plural-version-ford-focus.html
I found that, but then again it's just one person quoting someone else (referencing the 2nd post in that thread).