I need some help. I have a '14 SLT 5.3 with 3.42 gears and 2.5 level. My question is, I have stock 275/55/20 tires that weigh 39 lbs. I want to put on 285/55/20 Terra grapplers that weigh 58 lbs. That is 19 lbs more per corner but I'm leaving the diameter the same. How much rear wheel HP will I lose to the ground and how much will the weight effect MPG as well.