09-10-2022, 07:33 PM
As others have said, it probably takes a good ten miles before the engine is fully warm and giving of its best, so your 17 mile round-trip will certainly not give optimum fuel consumption. I assume you are talking about your 1929 chummy and that it is fitted with the standard updraught Zenith? In which case your filler is reasonably central in the car so your dipstick should give a reasonably accurate measurement; however, if you were on a steeply-cambered road driving on the right, that might well tip the car sufficiently for you to not be able to access the last half-gallon or so, as the fuel off-take would then be on the high side of the tank. Here in the UK driving on the left there is usually sufficient camber to drain the tank pretty thoroughly!
As for likely consumption, I can easily better 50mpg on a long steady-speed run (at say 45mph) whilst I would be disappointed to get worse than 40mpg in a day's motoring in the Peak District with perhaps 50% use of second gear (1931 RM saloon with 3-speed gearbox and standard FZB carburettor). I have never checked consumption on short-run local trips, but without getting the engine thoroughly warm (not just water temperature) I would not be surprised if it was no better than 30mpg. (all in Imperial gallons).
As for likely consumption, I can easily better 50mpg on a long steady-speed run (at say 45mph) whilst I would be disappointed to get worse than 40mpg in a day's motoring in the Peak District with perhaps 50% use of second gear (1931 RM saloon with 3-speed gearbox and standard FZB carburettor). I have never checked consumption on short-run local trips, but without getting the engine thoroughly warm (not just water temperature) I would not be surprised if it was no better than 30mpg. (all in Imperial gallons).