The programme was a bit flawed really as he was putting them in the wrong vehicles, you can still have a big efficient car, my 7 seat Grand Scenic does 40mpg around town and 50 fully laden when off camping etc, its not even the most efficient engine but still has cheap tax, so there are always alternatives I just reckon Quentin put the people who need space in the wrong motor, they could still get a bigger car and save.
Small cars only do their 45mpg on longer trips, on the school run or trips to the shops they will be down in the low 30s which would totally ruin his "savings" calculations.
Not really because a larger car will also experience similar drops in its economy when driven around town that the differential will be similar.
Finally you realise the best course of action with a reliable car that's worth very little is to simply hang on to it.
This is true, of course when it starts to cost you in repairs to keep it on the road, which was the point I though he was trying to make with MOT costs etc, as these cars on the show were likely to do a newer car with 5 years warranty and 20k servicing is not that costly, course you can't predict the future and know for sure what's going to go wrong but if you have a 10-15 year old car like those that you've had a few years and not spent much money on it chances are its going to cost you for something soon be it suspension/steering bits, clutch and brakes etc so its all about weighing up whether you want trouble free motoring in a new vehicles thats likely to be safer, cleaner, more refined and reliable vs plodding along and taking a chance.
How much value do you put on your time and effort, I know the last thing I want to do is hang around garages whilst they fix my motor, nor do I want to go out in the wet like this weekend and get my tools out much better things I can be doing with my time.