[oil pan 4]

I never did anything like a-b-a testing.
On the car I installed a proform (cheap, should have got a nice one) electric coolant pump, but at the same time I also converted to electric fans and that was about the time the car started having bad transmission slipping problems. So its hard to track any improvements on the car.

On the truck in addtion to the electric coolant pump it was part of a new engine build, installed a new set of tires, moved from sea level to 4300ft and changed my entire intake setup. The plan was to get the truck running 6 to 9 months before moving, that didnt happen, it was more like a week.
With the new elevation (12% less air here), new tires and different intake setup I am down about 5mpg from what I was getting in virginia during summer with the old engine set up and 10 year old 31'' goodyear RT-S tires.
I have a good data showing that on a smaller truck you lose about 2.2mpg highway when going from old goodyear RT-S tires to new yoko AT-S tires.
(its a good data set because my friend gave me his old goodyears and swapped them for the yoko AT-S and about 2 years later I replaced his old goodyears with yoko AT-S tires too).

Just converting to an electric coolant pump in cars is said to be good for up to 15% and up to 10% in a truck.

On the truck I did track a pretty clear 2mpg highway increase when I just converted to electric fans.

I don't normally have time to install just one mod and test it for a few weeks.