Me and Al get very similar commuter mpg's
that's too small a sample his car may also be out of tune and possibly not fully serviced
I might be wrong as I've not had a BGT for many years but I think I'd be very upset with 17mpg let alone 14mpg
Though she does need a tune up
perhaps suggests Al's does too, and note like all cars they like clean air filters
It's used no (discernible from dip stick) oil in the last few 100 miles.
However the rear carb does like to use damper oil.
that may not be, if it was both or none that would be more understandable, there was a thread which included all suggestions for damper oil to use
how you checked matching the pistons, here's a John Twist video on it - 41 Matching SU Air Pistons - http://www.youtube.com/watch?v=IfU47Oqq9wA
and carb tuning - 147 MG Carburetter Tuning - http://www.youtube.com/watch?v=4nvGLgO6pj0&fea...
and - 35 Tuning HIF Carburetters - http://www.youtube.com/watch?v=ASeMfXfjNpw&fea...
ETAA: First subzero start today. Slow turn over first few revs and then came to life. Might invest in a new battery just in case.
this cold snap and more so the next will show up starting and battery problems and battery stocks will drop but you could check your battery and connections first, even if you get a new battery it will still need good cables and connections
take the battery out and check the electrode level out on each cell and fully charge over as long as possible, clean the battery posts, the cable clamps and the battery earth lead connection, then check the cables are not corroded under the sleeving - check also at starter solenoid end and that the connection is clean, secure and protected
when you put your existing (or new) battery back in again check all connections are clean, secure an protected
poor starting can also be because of poor condition or connection of the engine/g/box earth strap so again check the connections are clean, secure and protected
a good habit to get into for any car but especially a classic is to reduce your unnecessary battery power consumption and to get into the routines of switching off all electrical items before the engine and to start the engine before turning on any electrical items