I'm getting some temperature probes to log data whilst running my car. If my radiator is doing it's job, what sort of temperature difference would I expect to see across it? I'm working on the idea that if there is a good gradient, my water pump isn't shifting enough water; and if there isn't, the radiator isn't shifting enough heat.

Regards,
Dave

Remember the thermostat get's into the equation until fully open....

A quick google suggests a drop of 20-25 deg.F to be common.