^yup, the 550i gets optimal gas mileage when the coolant is 102* C. If you drive it hard in the city, the coolant temp will drop to 90*C. These cars are basically right on the verge of overheating to deliver good mileage, and as a consequence the heat kills hoses, rubber seals, ect, much faster than other cars.

 

interesting. i wasnt aware the turbo motors ran that hot.

though, one advantage to running hotter, is that an engine runs cleaner. colder engines are more prone to carbon buildup.

 

I recently had my radiator replaced. I noticed a small puddle on my garage floor. It was not a catastrophic failure, it was drivable. The mileage at the time was 175,000.

 

The opening temp of electrically controlled thermostats is always high. The temp is controlled to various temps as the engine management desires. For MPG the thermostat will be heated to go wide open and then the electric water pump will be run at a low current as open thermostat reduces pumping load and much less current is needed to get water pumped through cooling system. Lower current requires less load on engine from alternator.
At low load the coolant temp may be controlled to 220F and under high load driving the coolant will be lowered to 185-190F for reduced likelihood of detonation.
When engine is started cold the pump may not even be operated if the heater is not needed for passengers. Hotter initial temp gets rid of condensation in oil from cold start quicker.
Cooling system functioning is changed significantly these days.

 

there's already a campaign out by BMW to address all of the issues with the N63TT engine. Man is that engine a turd...I thought my N62 was a pain in the crack, but the N63 is on a whole 'nother plane. They are having owners bring them in to check the injectors, timing chain for stretching (), carbon buildup, turbos, and various other things and getting replacement components. Finally, BMW is admitting how crappy this engine is despite the awesome power. Like someone else mentioned...I'm looking elsewhere for a replacement in the future...