Hobson's 3-litre XJ6 saloon gets about 28 mpg on methane (it used to get 30 on petrol). On his apple farm, he's got 10,000 trees from which he uses about 400 tons of pressed apples (about half his crop) to make methane a year. Not everything goes into the Jag, some goes to make hot water and electricity for the homes on his property. His Jag sees about 25,000 miles year, and he saves over £2,200 in fuel costs by using methane.
The initial investment in Hobson's methane system was around £25,000, but his car, farm and house are "now almost energy self-sufficient." Very cool.
Actually, this isn't exactly "fresh" news today. While it came to our attention thanks to this Top Gear story, the Mirror UK did the original reporting back in February.