How accuarate is the mpg

[pickemuptruck13]

Hey was wondering how accurate the mpg economy was on the gryphon? I am noticing a trend when i am doing 55 - 60 i am getting 16 to 17 as soon as i go over 60 it goes down to 13 is this normal for such a drastic drop Thanks!

[Jackpine]

Originally Posted by pickemuptruck13

Hey was wondering how accurate the mpg economy was on the gryphon? I am noticing a trend when i am doing 55 - 60 i am getting 16 to 17 as soon as i go over 60 it goes down to 13 is this normal for such a drastic drop Thanks!

Bill has answered this question in another forum somewhere. The problem is, the fuel flow sensor (and I just made that up - it's called something else) is not too accurate, and it can't account for some of the variables. So, the Gryphon actually gets its information from the PCM and it is, at times, getting information that really isn't quite right.

I've noticed I'm usually well within 1 mpg of what the Gryphon says (or what the info center on my dash says, since I have a King Ranch). One thing you CAN count on, if the display drops, you know your economy is suffering, so I use it more like a "trend" instrument.

I don't know that I've seen such a drastic drop as you above 60 mph, but the wind resistance force (drag) is increasing proportional to the speed squared, so, if you double your speed, you actually increase the drag by a factor of 4. However, at very low speeds, you aren't getting the best economy either. I think the "sweet spot", if there is one, is probably in the neighborhood of 50-55 mph.

Speed kills (your economy), and so will a headwind.

- Jack

[pickemuptruck13]

Well that makes since i was wondering how it calculated it. My truck is has a six inch suspension lift so maybe i am seeing a greater effect of wind drag once i am over 60. Well the good news is most of my driving is around 55! What kind of gas milage are you guys seeing? Thanks for all your help.

[Jackpine]

Originally Posted by pickemuptruck13

Well that makes since i was wondering how it calculated it. My truck is has a six inch suspension lift so maybe i am seeing a greater effect of wind drag once i am over 60. Well the good news is most of my driving is around 55! What kind of gas milage are you guys seeing? Thanks for all your help.

Much of this depends on your truck. I have the 5.4L engine SCrew 4x4 with 3.73 towing option gears and 275/65R18 tires. I also have a 200+# bed cap on it which sticks up about 6" above the cab giving both added wind resistance and added weight. So, I am not set up for fuel economy in this configuration.

On the highway, not towing and averaging in the 70-75 mph range, I can usually expect something above 15 mpg. Towing my 3600# trailer, at 65 mph, it becomes 12.7 mpg.

I am not a "leadfoot" coming off a standing start, and I don't brake aggressively. I'm probably in the 14's around town, but it's driven very little this way and Tucson has fairly high street speeds.

I suspect the lift IS hurting you. You're exposing more "hardware", under the truck, to the slipstream, which increases your frontal area drag. You're probably getting more turbulence under the truck too, but that effect may not actually be detrimental. Turbulence is not always bad.

- Jack

[Power Hungry]

Lifted trucks almost always experience poorer fuel economy due to the extra drag created by the exposure of under-vehicle components, not to mention the additional rotating mass of the tires & wheels. Even the width of the tire and the tread pattern can add to the wind resistance.

As for the MPG, the Evo/Gryphon uses the MAF sensor reading to calculate the amount of fuel being used. There are times when it might be slightly inaccurate, such as under WOT acceleration, but these situations are infrequent and "weighted" so that they are given proper consideration.

The thing to remember is that it isn't the final word in fuel economy... A pen and paper is. As Jack said, it should be used more as a means of measuring trends. For what it's worth though, I've found it to be more accurate than the MPG calculation in our Expedition.

[Jon Roseman]

I haven't checked my mileage on my trip divided by my gallons yet but I did notice that all of a sudden my gas mileage on my gryphon has dropped and I have no idea why. It did say I was getting around 17mpg at 65-70mph and now I'm lucky to get 13mpg at the same speed.

[Power Hungry]

Did fuel quality change? Buy gas at a different station? Extreme weather change? All hugely important factors. When it started getting cold, we went from 19+ to around 17. Darn oxygenated winter blend fuels. :P

[Jon Roseman]

ya it could be.....but the truck is still fast so who the hell cares i guess