Occasionally there is a thread about mileage so I thought I would share some results from a recent trip.

I have a 2003 F350 CC 4x4 FX4, 7.3 auto, 4.10 gears. The truck is completely stock with the exception of 285-75-16 tires instead of the factory 265's. I also have a canopy.

I recently made a trip from Lafayette, LA (altitude 5') to Farmington NM and up into southern Colorado by the Navaho State Park (elevation 7500'). I left Lafayette with a mileage of 13.8 mpg (averaged over several months, I did not reset the mileage either). By the time I was in western Tx my mileage had increased to over 14. By the time I got to Farmington it had climbed to 14.7 mpg (remember this is averaged with the 13.8 from before). I drove around the mountains for 2 weeks before driving home. I reset my mileage when I fueled up in Farmington. I started the trip with 16.7 mpg (alt 7400', 81 F). I filled up again somewhere in west TX and again east of Dallas. By the time I got to Dallas my mileage had dropped to 15.3 and by the time I got back home in Lafayette it was right back at 13.8 mpg (the temp in Laf was 81F as well....overcast).

So what gives? Is it all the change in humidity? Colder air @ 7400' has more oxygen then warmer air @ sea level? It wasn't even warmer when I got home but alot more humid.

At first I thought maybe it was the fuel but the mileage dropped continously throughout the entire trip.

The whole trip was about 2800 miles so it should be a good representation I think.
Any thoughts..

 

was this hand calculated or lie-o-meter?

 

It was straight off the lie-o-meter ( I assume you mean the overhead console). I checked it once last year and it was right on with my hand calculations so I tend to trust it. I have started keeping track manually again to verify its accuracy again.

 

The console is strictly a computer calculated estimate, there is no way it will have much accuracy over various driving conditions.

 

Is this how Ford does it? I am not trying to be a smart A here, I am really curious. In my experience with other maker's mileage computers, they are pretty accurate.

IE - Fuel calculations are done by taking how long the injectors are flowing (open), the rated pounds of fuel flow per hour and then the the miles driven. This uses the same as I would use to manualy (fuel used / miles driven) check fuel mileage, with the added benefit of being able to have a "instant" fuel mileage available.

I can see where it would not be accurate at all if you had made modifications such as higher rated injectors, etc, but in stock form it is very accurate, but I guess that is not how Ford does it ?

Just curious - David

 

I experience better fuel milage in cooler temps with my 350
in its better days around town in SW Fla 14
interstate driving SW Fla 16
mountain driving 18-19

 

Thats weird... Maybe your tires swelled up at high altitude and fooled the computer..LOL

 

ain't no computer done the olde fashon way
think it has something to do with cooler air

 

'computer calculated estimate' may be a little misleading because the computer does monitor many of the sensors to calculate the fuel mileage but I think the algorithm that Ford is using is the problem. Even stock, mine was way off. I think that is why so many users have dubbed it as the 'lie-o-meter'.