-fad is absolutely right ... I left the radiator out as a separate issue, however, it is pretty clear that, if the radiator is not operating efficiently, that the increase in airflow might be enough to overcome a lack of efficiency ... however, this seems a longer shot in 45F weather ... the engine should have a VERY hard time overheating in this kind of weather.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg