i-DSi, there may be some merit in what you say as well...the cooling systems on each car are designed for the conditions encountered in each car...the Geo has a small grille opening and a shrimpy radiator, whereas the Cad has a very large grille opening and a large radiator. I expect that the engineers who designed both cars designed them for similar warm-up and cooling characteristics, despite the difference in the size of the engines and cars.
Joe, I had other thoughts why a smaller engine should warm up slower (but I'm not 100% sure!!) if they are driven economicly or hypermilestyle:
- the smaller engine has more load and this results in more efficiency => higher % of burnt petrol is used for moving the car, not for heating engine
- they are generally combined with manual transmissions (AT's consume extra fuel=>quicker warm up for AT's, slower for MT's).
- smaller engines are found in smaller cars: less power necessary to move the car => less burnt petrol means slower warm up.