Mine does around 23mpg on a long run at a steady 56-60. If you have a SWB consider changing upto 7.50 LWB wheels (but change the speedo as well!) Pre Overdrive it was around 20mpg. (5MB motor, weber carb, std dizzy, FWH). I've since changed to an electronic distributor supplied by Simonbbc which has helped it run a little better, apart from icing in the carb it has fired up even in the recent -10 or so temps! My next steps are some road tyres and a 1:9 ACR head, we'll see what the difference is! I did add some molyslip to the gearbox which made little difference to consumption but reduced noise, especially when added to the overdrive.