I don't really know where to post this but I'll start here. I had my custom tunes from PHP come in and just finished my first good long (7 hour) highway journey. I was severely disappointed in my gas mileage. I have Toyo 33x12.5R18 MTs which will contribute to poor mileage yes, but 12mpg avg? I reset it several times throughout the trip. I get better mileage in the city (14mpg) which really makes no sense. I'm running the 87perf tune and the truck definitely has butt loads of power but cruises at 75mph between 54-60+ load. This across the flat prairie. At one point I was averaging 11mpg. Is this normal? It seems hugely low, considering before I could haul a trailer through the mountains and get 11mpg. Before with the canned tunes I was getting 17mpg on 91 octane.

I'm hoping to switch back to the stock setting and go for another drive tomorrow and see what difference it makes.

I did a search and it would seem that I'm on the bottom end of the mpg spectrum. People with much bigger tires than me get my mileage. Hopefully will by the end of tomorrow, I will have some stock tune mileage numbers to compare against so we can better tell if its the tune or something else.

Thoughts or opinions anyone?

Info (whether you need it or not):

Ambient temp : -18C (0 Farenheit)
Intake Air temp : 8F
Truck : 2008 4x4 5.4 3V, 1.5" level, 3.73 gears
Speed : 75mph
Load : 54-60+
Engine Temp (CHT) : 206F
Trans Temp : 155F
Fuel : 88 octane (other choice was 85.5, figured higher was the better choice)
Tires : 33x12.5R18 Toyo MTs; 45psi front, 40 psi rear
Tune : Custom 87 Perf (PHP)

 

Have you applied speedometer/odometer corrections for your gears and oversize tires? How much ethanol was in that 88 octane?

 

Winter gas taking it's toll? Like GLC - high ethanol?

 

Instead of relying on an electronic gauge you need to do hand the calculation method to be more accurate on mpgs......another thing is winter is upon us and it just so happens that most gas suppliers have started to supply winter blend fuel.....that means crappy mileage for the next four to five months.....
Anymore questions or concerns don't hesitate to call Bill at PHP.....

 

I have to agree. Hand calculations are the most accurate. I, by hand, calculate an average of about 13 mpg. I have an '07 4x4, 18" wheels w/ stock tires and 3.73 gears. Only performance mods I have are the Gotts mod and a Magnaflow SI/DO exhaust system. No tuner yet. I would think your tires and lift are probably causing most of your mpg loss. If your getting a tuner in hopes of drastically improving your mpg's, you are going to be dissapointed!!!

 

when i got my edge, i def noticed an increase in power, but nothing in mileage.

 

Yes, all the nessecary adjustments have been made. As for how much ethanol was in the gas, I can't really say. It came from a Conoco station both times.

Definitely have a large dropped in mileage though. I just did a hand calculation for it and technically averaged 11mpg.

Different fuel in it now so we`ll see how it does today.

 

2 weeks ago when I filled up I was averaging 15.6 consistantly.....now after the fill up yesterday its down to the 13s so I do know either I got crappy gas or the winter blend has hit the market.....it will be two more weeks before I fill up again to confirm.....

 

with 33" tires cruising at 75mph with 3.73 gears is not the best for fuel economy. I bet if you would slow down about 5-10 mph you will see a pretty good increase. Also like others have stated you have to think about the winter blend fuel.

 

Speed will always be the number one factor in attaining good MPG. Anything over 70mph and my mileage nose dives quickly. If I keep my speed around 60-65 I do very well. Winter gas in the Toronto area combined with sub zero temps and I my mpg drops around 25% and sometimes more. Not to mention gas prices up over 10% in the last month - double kick in the nards.

 

And just to emphasize something here. Have you confirmed that your odometer is telling you the truth now? It's very easy to set up the Gryphon so that it's lying to you. I think your mileage is too low, even given the bigger feet you've installed on your truck.

If I'm not towing, I get 15.0-15.5 mpg in my SCrew with 3.73 gears and 32" (OEM sized) tires. This is highway driving, with little wind and on relatively level ground. A head wind will severely impact your economy, and so will a road that "climbs".

I honestly think your odometer is not telling you the truth though.

- Jack

 

I know that according to one of those speed traps that flash your speed and 30mph its bang on but that doesn't mean much for higher speeds. I calculated the tire size should be 2554 I believe, and what came with the tune was 2596, which in theory would give me artificially high gas mileage if in fact 2554 was the correct size would it not?Still could be wrong but the manual method did show it was 1mpg less than what the gryphon showed. For the record I did double check before uploading the tune that the gear ratio and everything was set properly.

As an update. I was back on the highway with a tank full of different fuel. This time true 87 octane. Average approximately 13-13.5. That was with about a 5 mph, 90 degree cross wind. Doing 60-65mph I was averaging 15-16. Still not that fantastic but better. I should mention that this again is the gryphon reading. Couldn't do the manual method as I did a ton of siting and idling and city driving in 4x4.

Still wanting to switch to stock and test it on that premise but it keeps getting colder and colder and I'm not a fan of reprogramming the PCM in the freezing cold. I still hoping that the -20s is having a large effect on it mileage too.

 

You're on the right track there!

 

OK, 2554 is EXACTLY what I would have recommended for TS! But, of course, this is a starting point. I would not be surprised to see some adjustments. Still, the "radar" reading is a good sign - was it agreeing with a Gryphon speed or a dash speed? In the 30 mph range, your dash speedo should normally read about 1 mph fast (which is about 3% high). You'd like your dash speedo to read about 31 if your "real" speed is 30.

And then I have to agree with 88 regarding the fuel usage in VERY cold weather. Yes, the winter blends give you worse mileage (because you want to be able to start the thing when it's very cold), but, because the air is much more dense at cold, dry temperatures, you are going to be feeding a higher fuel charge to each cylinder to maintain the correct A/F ratio. So, you've got a "double whammy". The upside is, you get more power.

DO NOT program the PCM unless the engine, PCM and the Gryphon are all warm! Doing it right after a long drive with the cab nice and toasty is a good bet. (This advice applies to ANY programmer!)

- Jack

 

It was agreeing for sure with the gryphon, and to the best of my eyesight the dash too but I can't discern 1mph difference. Kilometers is on the outside for me. The miles per hour are the tiny little numbers in the center.

Little update, tranny hasn't been smooth lately, albeit much smoother on the stock setting. Mysteriously been loosing fluid since getting it serviced. Truck goes in tomorrow for that. Could also add to the loss of mileage. Really thinking its a combination of numerous factors leading to this.

PS what kind of ruddy adhesive tape comes with those gryphons? It took the paint off my grey dash panel when I tried removing it (can't let the stealership know I had a tuner and get away with trying to void my warranty). Kind of choked about that, now the pod HAS to stay there when the truck is all fixed, hide the ugly patch. Damn shame. Definitely no 3M double sided tape.