[brucepick]

We should make this point re. auto tranny:
(In case anyone here's considering coasting with engine off)

Auto trannies usually have restrictions on coasting with engine off.
That's due to the tranny's input end driving it's lubrication system.

Check your owner's manual for flat towing. If the car can be towed with all four wheels on the ground at any speed then you can coast with engine off. Often it will say, for example, up to 20 mph and 20 miles distance. My old Volvo, 40 mph and 40 miles. Saturns often have no restriction; you see them towed behind RVs. Some years Saturn require that you remove a couple fuses before flat towing.