Thanks for the suggestions.

OK Forgive me if I have forgotten one in my response.

The efficiency went over time (6 plus months)

The tires are 40.7 pounds by the website specs for this size so I don't think that is the issue. Plus weight would affect city driving more than highway. It is my highway that has really suffered. Last fill up was 95% flat highway and WAS WORSE than the fill up before with up to 25% city. (Rare occasion running kids around the city for a swim meet.) Tires are inflated with nitrogen and have been checked for pressure since the drop in temp.

When the truck was new I was running winter gas and getting over 19.5 mpg so I do note a drop in all my vehicles for winter gas.. but also think this can't be the issue as it is a gradual loss over 6 months or more.

Brakes have been checked and no problems there.

Just really mystified at this as traveling at 70 mph constant speed should get better milage than stop and go to 35 every 1-2 minutes. (Typical Vancouver traffic.) My latest readings are 14.1 MPG with almost all highway driving.. the one before that was about .5mpg better with MORE city driving.

Any other suggestions? Can a transmission cause friction without making noise or smelling badly? I am suspicious of this component as it seems to always be lugging the engine and kickdowns take almost full throttle... But then again at speed gearing should not make a difference unless the bearings are shot??? Can any of the shafts do this without failing or leaking?

Drives great except for the transmission lag... but I chalked that up to Toyota trying to max out gas milage with low revs.

It is a real mystery... talked to an old friend that was one of the crew that worked on my formula mazda... great race car mechanic... no ideas about this 4runner however.

Any Dr. House types out there that specialize in 4Runners?

Thanks