With winter here, it is pretty hard to tell the effects of things, so I'll probably have to wait till around spring time for the tailgate test, but I suspect either way it won't effect it much.
The 10-15% drop I saw in FE with 4x4 on was with the odd ball tire up front (larger), low tires, and driving though snow. Now with all the same sized tires and tested on clear roads, I don't really see a change. The catcher with how my truck is setup, the front wheel hubs are direct locked in all the time so my front diff is always spinning. I'm sure once I get the manual lockouts swapped over that I'll see a new gain while in 2wd
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I haven't drove the truck much, but it seems FE hasn't really changed except in the distance before I'm getting warmed up numbers. I might be getting slightly better MPG while cold. I have not changed the trans / transfer case fluids yet, hoping to within the next week or so.
I won't have any SC numbers for a long time, I have a couple of other projects that need the funds before the SC. The claimed numbers were from sites where people are looking to either make their trucks fast or go though more mud, so their numbers are probably nothing special to go by, one claimed a drop 1-2mpg, and 2-3 claimed either no change or a slight increase. Depending how things go, I might get a Camry v6 manual and do an engine transplant into it with another Tacoma/4runner 3.4L
. According to my research the swap is a mechanical direct bolt in, electronics are another story though.
Also question for ya mikeyjd, I see the last 3-4 tank fill ups are a steady increase in MPG, the temp hasn't done the same thing, so what are you doing different? I'll take a stab and guess you were P&G, seems my truck loves predicted stops, MPG before the coast vs MPG after up to speed is always higher after the stop for me.