About a year ago (11 months) I bought the bully dog GT to see if I could gain back some mileage after fitting larger tires and a small lift. I use my Pathy for work, drive a lot, and tow a small 8ft trailer regularly. my fuel bill is around $1000 a month. I've put about 50k miles on since installing the tuner. results and specs as follows.
(disclaimer because the internet is full of overly litigious douche nozzles: your results will vary and I am not responsible if you blow your truck up. these are simply my findings over a long term test in my own personal pathfinder. all mileage was calculated by three sources: onboard computer, trip odo/fill up method and bully dog. all three were so close together there is really no discrepancy to note.)

specs:
2005 4wd 4.0 liter VQ40 box stock 156k miles ( don't consider a K&N a "mod")
rancho quick lift
265 75 16 goodyear wrangler authority C load range(yep the walmart ones...love em)
and bully dog tuner of course.

what I have found:
1st: I can find no measurable mileage difference between a/c on or off. even the instant mpg reading on the GT shows no difference on any setting... even set to stock.

2nd: the ideal unloaded highway mileage speed in any setting seems to be right around 75mph. who-da thunk it?

3rd: this tire size makes the speedo/odo dead nuts accurate, verified by radar(police friend) and gps.

4th: my mileage went from 16.7mpg avg. to 15.3 (some mileage discrepancy because of tire diameter having an effect on the reading) after the lift and tires. sure on straight highway trips I could still get up to
19ish mpg, but before I was able to get 21-22mpg on long trips.

5th: 87 octane setting/87octane fuel avg: 15.4 mpg.

6th: high test setting/high test fuel (91 here saw no difference with 93.)
15.5mpg

7th: (not recommended) high test setting/87 octane fuel 15.7mpg.
there is a little bit of knock at part throttle pulling way from a stop, but no more than I ever noticed in purely stock trim with ethanol blended fuels. the only time I don't get a little bit of knock is if I can manage to find pure un-government-adulterated fuel but then mileage also goes up significantly without ethanol.

8th: long highway trips I can get up to 20ish mpg.

in conclusion my advice is not to expect huge gains or to even get back to square one and also don't expect for it to pay for itself in fuel savings unless you drive a shit ton. but if you have the extra jingle in your pocket, it's not a bad little device to have. it definitely puts a little pep back into your pathy's step, but not a lot and there are some nice monitoring features. for big gains on the mpg front your best bet is to invest time in your right foot. driving habits make more of a difference than anything else. I also feel that one of the biggest detractors is the transmision. although it is very smooth and buttery slick. top notch as far far as slush boxes go. It just feels to really soak up a lot of energy as most autos do. I would love to find a manual either out of a euro market truck or perhaps a frontier to drop in. I think that mod would be good for at least 2-3 mpg. good luck and hope this helps to answer some of your questions out there.

Thanks for the Bully Dog report. Check that off my list. I am a current owner of ScanGauge 2. Love it.
To be frank, seems the PF is about maxed out when it comes to improving MPG. Some items that may help are to stick with tire size spec’d. I notice that the torq converter tends to unlock when engine load increases. Yes, I hate this transmission also. But to swap a junked Frontier or Xterra manual power train into a functioning vehicle may not have a cost advantage. Just next purchase, I will look strongly at a manual version of ???, but those are harder to find. Course those 8 or 9 speed trannys sound good. Can’t get me to trust PF CVT’s… yet.
I use a P rated tire inflated to 40-45psi. LT versions give a harsher ride & worse MPG.
Last yr I went 700 miles to NY & did cruise control at ~67MPH. Got a little over 21 with prem. Locally, 150 miles on a 4 lane country state road at <50MPH, got 27.7MPH.
As for ethanol-free, I agree. Hard to find but gives 12% better MPG. Right now, testing “Ethanol Defense”. Problem is that stations have switched to winter formulation & temps are cooler, so can not comment at this time except that the ”Long Term Fuel Trim” (ScanGauge2) shows similar numbers as if ethanol is reduced, similar to the readings of E0 gas.

On a side note, hope you have swapped out your radiator, because you are due for trans failure if it hasn’t been done yet.

Your dead on about the right foot being the biggest key to getting the best mileage. I think a lot of it has to do with the electronic throttle system. Also, I use cruise control as much as possible. I average about 17.5 mpg on my stock 06 LE AWD and can get 21.5 on a long trip of interstate highways and 75-80 mph speeds.

Damn, you guys are lucky. I average maybe 14 city 18 highway on a good day. I guess these heavy Nissan's aren't built for the city

RedPathy wrote:Damn, you guys are lucky. I average maybe 14 city 18 highway on a good day. I guess these heavy Nissan's aren't built for the city

Interesting you say that with an Off-Road model. With the noted difference in speedometer accuracy between the OR versus the other models, you would think the accuracy of the other models (S, regular SE, LE)would be a little off, as well.

smj999smj wrote:

RedPathy wrote:Damn, you guys are lucky. I average maybe 14 city 18 highway on a good day. I guess these heavy Nissan's aren't built for the city

Interesting you say that with an Off-Road model. With the noted difference in speedometer accuracy between the OR versus the other models, you would think the accuracy of the other models (S, regular SE, LE)would be a little off, as well.

Thats even with a light foot. I typically drive 100% city and frequently average 13-13.5 per tank. That is the calculated value as well. I couldn't tell you how accurate the value is on the screen since I reset it many times to try and get it to show me a higher number, lol. The MPG screen is so depressing I usually just use the DTE screen. I may be purchasing a BDGT soon to see if I can help that at all.