What kind of hand calculated fuel mileage is your 08 getting, CampD? How does it compare with and older diesels such as 6.0L or 7.3L psd? A couple of years ago I was talking to a fellow that had an 08 6.4L and he was getting about 1 mpg less than my 6.0L. I averaged 16-16.5 on the highway at the speed limit. He wasn't too impressed with his 08. He had a 7.3 before, so that might be some of his frustration factor. His 7.3L consistantly got 18 mpg on the highway and it was totally stock.

 

You obviously missed the point of my post.

 

Did a 700 mile run past three days. I averaged 15.4 on the way out. Cruise set at 74mph most of the time, 65 once I got on Hwy. 74 going East from I-95 to Wilmington, NC which is about 75 miles.

Took pictures of my dash on the way home. Got good numbers as I think I had a decent tailwind most of the day.




The above is to show what cruising at 65 mph for 75 miles or so can do.



This is after 75 miles of cruising @65, then 200 miles cruising @ 73, then a few miles of roads to reach my destination, 35/45 miles an hour.

I had the A/C on, Motorcraft Cetane additive (4 oz. per tank), and no load or trailer. Just two guys and our luggage and some tools.

 

Now that I have filled the fuel tank I have a different story if anyone is interested. I had no idea the truck's computer could be so far off.

299 miles, 20 gallons of fuel to fill up, 14.65MPG. Still good but not 17.

 

I guess that's why a lot of the guys on the other forums call the trip computers lie-o-meter. But still, that's not real bad for mileage with an 08. It seems to be what most are reporting for the conditions. Some of the sights I've been to say that with the DPF removed and a program to eliminate regeneration cycle the mileage improves by 4mpg. I'm not real sure if the risk of getting caught by the feds is worth doing it or not. It's said to cost around $1500-$2000 to do. It could be lower than that. But still, an additional 4 mpg would put your rig at 18.7mpg. That isn't bad for a heavy rig like that.

 

We all need to stop depending on the "lie-o-meter" to tell us how we're doing MPG-wise. The fact that it only delivers "an average", and that average is somewhat dubious, means that it really isn't the correct instrument for the job. I'm ordering a scan-guage for my Super Duty today (I already have one in my Honda). It will tell me my fuel flow, real-time (live, not average) MPG, and even cost ($) per mile.

 

I would love to have a real-time average displayed! My wife's POS 1996 Dodge Caravan had it! My overhead console is not the most accurate, but it's not as bad as others. Unless I really cycle the driving style (lots of sporty or stop-and-go and then long highway cruise), it's usually within .2 MPG overall. If I change styles, especially towards the end of the tank, the difference can be up to .5 MPG overall. I always hand calculate at every fill-up, but the lie-o-meter gives me a good indication (although not exact) of how I'm doing for the tank.

 

There are two reasons I keep track of fuel mileage. If I know what my fuel mileage is under most driving conditions, I can plan my fuel expenses for my trip better and I know what my range is between fuel stops. The second reason is to tell if something needs attention due to a drop in mileage for no explainable reason. I didn't buy a full size pickup for fuel economy, but I do expect it to get reasonable fuel mileage. I don't hyper-mile, but I do drive conservatively on acceleration and steady on the highway. I do not use the cruise control for safety reasons. There are too many morons on the road that don't pay attention to their suroundings to make cruise safe in my opinion. Besides, it never helped my mileage any. I never use cruise while towing. It's too hard on the truck and unsafe. If I wanted something for maximum fuel economy I'd be driving a VW TDI.

 

Just a quickie on the ol' lie-o-meter... I've found that mod chips, at least my bully dog, have a profound effect on the meter. I compared my results from the meter to hand calculated results since the meter was telling me that I was getting like 25 mpg with the 120 hp setting and 17 mpg with the 80 hp setting. That seemed bass ackwards to me so out came the calculator and guess which one was lying... It was more like 15 mpg with a decently heavy foot at the 120 hp setting and around 17 mpg at the 80 hp setting with the same rather heavy foot... That, at least, seems to be more consistent with reason...

Chips are great for power and torque, but if you're rolling coal you'd better cut the ol' lie-o-meter in half...

Just my .02 worth...