Questions Dodge Durango 2008

Hello,all and happy holidays. My name is Mag and I have been a previous Durango owner, till some jerk in a truck sideswiped me while i was getting onto a highway and he was getting off the highway. My Durango was a 1998 and it had 160K on it and it was still running great; never had a problem with it. I was going to try and keep it till it became a antique I even had the engine steam cleaned and the water or snow still beaded up on it great wax job. Well anyway sad to say it is gone now totaled, I got money from the insurance company and got a 2008 Durango ( couldn't afford a new one) with great mileage, and it also runs great.

My question is after reading the manual, I still don't understand how the EPS works. I have been experimenting with it and if I shut it off i seem to be getting better gas mileage than when it is on. Is it safe to have this off all the time, and is this also the 4wdr? It doesn't say it on the truck or in the manual, but that is how it was advertised and on the paper work from the dealer. Any response to this will be greatly appreciated; thank you in advance for your responses.