Hello everyone.
I've got an S60 Bi-Fuel as well. 03 plate. Bought last June with 110k on the clock, now got 145k on it. It's cost me 14.65 pence per mile.
The tech specs on
this page say it has a 50 ltr gas tank and a 30 ltr petrol tank. But I've never got more than 45 ltrs of gas in mine, even when filling from empty.
I do well to get more than 22 mpg at the moment. I have a heavy right foot, but I don't get any better economy even if I keep it below 3k revs.
It's due a service though. Below 2k revs it's very rough. I suspect a fuel supply problem cos it runs fine on petrol.