The main improvement in engine fuel economy can be found in the use of electronic fuel injection and mapped ignition.
A lot of people are fitting older cars with carbs and clockwork ignition with DIY engine management units, like Megasquirt.
The results are often very illuminating, with much improved economy, performance and drivability. Reliability is another factor, most running problems with old cars could be attributed to ignition or fueling issues, usually the former.
Modern cars are technically accomplished, but in many cases I think they are far too heavy, which offsets a lot of the advances, and the prices levied for servicing these days beggers belief.
Andy
