I have the 4.0 in a 2018 4runner. The reason I bought it was the complaints on the 3.5 engine and ever shifting tranny.
My 4.0 gets 20 mpg. I bought a really nice aluminum trailer, so I think I did better than just a Tacoma. More inside room for the dogs, and I think the engine is better. The newer 4.0 does have the sucky oil filter, but it is not too much of a big deal. I have no regrets with the 4.0, but I cant imagine less HP with the 3.5. The 4.0 is adequate at best.
