Just got my Defender LTX M/S 2s (275/65R18) on my 2017 LC last week, along with swapping out the wheels for Tundra steelies. I was surprised it added 13 pounds per wheel. I was ESPECIALLY surprised that 8ish pounds of that was rubber not steel! Previous tire was a Michelin Latitude in 285/60R18.
Honestly, I'm not really sure if I can feel much difference due to the extra weight...
maybe it feels a little bit harder to stay in Eco as I accelerate? MPG doesn't seem to be impacted based on one tank of gas. Not saying that it's not there, just that I'm not that observant.

I'll keep an eye on it, and maybe swap back to stock rims or something new if I convince myself I need the weight back (the Defenders are staying!).