I've had two 1.0 FIRE engined Uno's, and asides from the ancillaries (starter motor, alternator, distributor etc. which don't count as they aren't part of the engine design) I've never, ever been let down by engine failure in over 50,000 miles of driving.
Considering the FIRE concept is nearly 21 years old, it is still a revolutionary design. It's compact, light (especially considering the block is cast iron), torquey and very strong. It also used something like 20-30% LESS parts than the old pushrod engine. Less things to move = less weight = less things to go wrong = better efficiency.
On a run I've achieved 60 mpg, and round town never less than 40mpg. It's mid range torque is suprisingly strong and it has no problems with keeping up with modern day traffic.
In 8v guise, it isn't the most revvy of engines but that appears to be more down to the valves being restrictive. 16v and MPI versions rev better as the head flows more due to bigger valves.
It is a bit raucous at higher revs, but nothing like some of the engines that were around when it was released! Compare it with the BMC 'A' series engine and the Ford Crossflow and CVH and it is light years ahead.
Someone mentioned a weak point of the headgasket, but I've never suffered a failure (famous last words!) Like a lot of cars, failure is more likely down to the fact that the cooling system is never serviced. The coolant loses its anti corrosion properties over time, and the remaining coolant then does a good job of eating away the headgasket leading to failure. Flush through and change the coolant every couple of years and the headgasket should give hardly any trouble.
Saying that, the headgasket appears to be a weak spot on Cinquecentos and Puntos. I'm sure I read somewhere that it was down to lower torque settings used by the factory for some reason. Maybe if they were tightened down to the orginal torque there would be less of a problem?
The FIRE is getting a bit old now, but it still holds its own and is still a great engine. Don't forget that the MPI and 16v versions bring it up to date! I wonder if I could fit one of those into my Uno? :chin: