My current '07 Toyota Tacoma V-6 4x4 (245hp) Access Cab (5 spd) Automatic requires me to be in D4...NOT OD when I TOW. I have a 3,000# trailer/boat. I get 21 MPG on the highway w/o the boat. With the boat I get about 16 MPG in D4. My rear end ratio is 3.73. It is adequate..
My OLD (142,000 miles) 1995 Tacoma V-6 4x4 (190HP) Access Cab STICK (5 Spd) got 27 MPG on the highway W/O the boat and 21 MPG WITH the boat.... going over the mountains from the LR to Rutland, Vt to Lake George.
My new truck is nice because it has all the STUFF that the old truck didn't have..A/C..power windows..etc.
BUT..the old truck was a real working truck...the new one is ...well.. comfortable.
NB