6 speeds, can we drop out interstate rpm's with differential gearing ???

There is a difference between rolling resistance and rotating mass. Of course, someone who does this sort of thing for a living (or even a slight grasp on the laws of physics) would understand this.

 

As for changing the 6th gear ratio, It is my understanding from a thread here or on TN many moons ago that the 6th countershaft gear is a "cluster" with a couple other gears and the shaft, so no quick and easy gear swap is possible. I too would like to have a higher 6th gear ratio, but unless I have a need to replace my tranny, it stays how it is. I would look into the FJ tranny myself. Since the engine, clutch are the same, and the FJ t-cases bolt up to the tacoma tranny, I would expect a drop-in fit.

 

I am BELOW sea level, fairly flat terrain, the weather has changed from one day being in the 70's (f) to the next day in the 20's with humidity ranging fom 30% to 150%. I have put 5 tanks thru the truck. all city/hwy combined (cruise control is busted). I have not hauled anything heavy, just a supersport and various race gear a few times.

1'st tank of 87 (all 10% ethanol) went 210 miles on 16gal
then I started a full tune up, changing all gear fluids, engine oil/filter, spark plugs, completely remove and clean intake/sensors (it was pretty bad) seafoam in gas tank.
2nd tank of 87 after tune up, went 210 mi on 16 gal
3rd tank of 87, went 230 mi on 16 gal.
4th tank I switched to 93, went 240 mi on 16 gal
5th tank put 93 again, went 260mi on 16 gal
6th tank had to put 87 gone 5o mi so far

and this truck is pretty darn loud at 60mph.
yesterday i removed the pathetic flat 3leaf stock springs and installed general spring HD packs. This may also have an effect.

This is much better mileage than my dodge ram 4x4 I used to have. But still not as great as I would expect. I imagine it would get maybe 10 more miles out of the tank if the cruise control worked. But cruising on the interstate at 75 mph is definently getting worse mileage than on the 2 lane hwy at 50 mph.
It almost makes me want to take my wifes dodge ram (also 6speed manual but 6th gear is what you would expect it to be). It probably weighs close to 2,000lbs more than my little tacoma and it gets closer to 20 mpg's. in that thing 73mph in 6th gear is at 2k rpm's.
and if you look at the numbers, our V6 makes similar power to the dodge 4.7L V8

 

QFT

I slowed down from 72 - 65 and went from averaging 16ish to 18.5 instantly (winter blend of gasoline). I expect to see 19.5 average when the summer blend gasoline comes back.

 

I see that is what I would call poor mileage... I have a friend who get about 12-13mpg in his no matter how his drives it (around town, 65 mph on the interstate, 85 mph on the interstate) he can't figure it out and his is an auto.

I have added so much armor that I am almost 2000lbs over stock (about 6000lbs total) and I live around 5000 ft with lots of hills. I drove from Colorado through Utah to Idaho. Half of it was 65 mph and the other half was 75 mph. I set the cruise for 5 over and just let it do it's thing the whole trip and I averaged 17-18 mpg for the trip and I still typically average that when my driving is pure interstate. Around town my average is down to about 13 mpg though. It's a mix between having all the extra weight and not being able to keep my foot out of the throttle on take offs (what can I say those 4.88 diff gears are torquey). Oh and I always run premium gas in mine.


My question is, how are you coming up with your gallon numbers? You are right on 16 gallons every time which seems suspicious, unless you were just rounding I guess. I top my tank off everytime I get gas and then just use the amount of gas I just put in (read from the gas pump) as the amount of gas I burned the last X miles (read from the odometer, and adjusted for different tire sizes)

I've seen some people do some funky stuff, where they say they are at a quarter tank so they must have burned 21.1 * 0.75 = 15.8 gallons, which isn't correct. The fuel gauge estimates way low. In fact when it says empty you still have like 4 gallons of gas left.

 

Mythbusters is 90% entertainment, 9% BS, and 1% science. (my own estimate, opinions vary)


From the folks who do this sort of stuff for a living...

"a one kg/ton improvement in rolling resistance (about 10-12% of current average values for passenger cars) results in a fuel savings of about 0.835 cm3/km traveled per ton of vehicle mass. If the average vehicle mass is assumed (conservatively) to be 1600 kg (3520 lbs.), then the estimated fuel consumption savings possible nationwide by a reduction in the coefficient of rolling resistance of 1 kg/ton is 1.5 billion gallons of gasoline per year. This figure is based on year 2000 data from the Federal Highway Administration (FHWA) of 2.7 trillion vehicle miles traveled (VMT) annually in the U.S. Since the significantly higher mass of trucks results in even larger energy consumption associated with the tires, the total potential savings due to the same level of improvement in rolling resistance is even larger when all vehicles are considered."

http://www.nhtsa.gov/staticfiles/safercar/pdf/PneumaticTire_HS-810-561.pdf

 

The largest MPG factor under our control

http://www.fueleconomy.gov/feg/driveHabits.jsp

 

I fill up right when the light comes on. And it takes exactly 16 gal. then I just look at the odometer.

it looks like my mileage is consistantly improving? strange? I am not changing my driving habits.