e85 or stay with pump gas

You don't want it.

If you are N/A and driving on the street, it's a waste.
-it runs cooler because you are putting more fuel through the system, so that cooling comes with reduced MPG
-higher chance of contaminated fuel unless you are running it often, and keeping the tank fully topped off.
-higher chance of contaminated fuel since it sits in tanks much much longer at the gas station since it's not as popular.

I have two below ground MOGAS tanks where I work. For years the components have been basically rust free. With the military now using E10 for all our MOGAS, the rate of deterioration is outright FRIGHTENING. It's not even regular rust, it looks like the old black firework snakes, but made out of rust. It's a puffy rusty slag that is growing on everything around the probe well.
I would pass on it. If you are wanting a cooler engine and better MPG, I'd give FiTech a look.