I have just over 5000 miles on my truck. I calculate my mileage per tank and I have my trip B set to an all-up total.

My all-up total was 17.9 up until I got home from a 2000+ mile trip up north. On the way up the truck was over 18mpg. On the way back it was about 17.4 (averaging from the tanks, trip A and mileage screen). Since the trip miles I've filled the tank once (although we filled up within a couple hundred miles of home on the return trip so that tank lasted a little while). My mileage this tank, and I am about 1/3 through it, is below 15.5. For reference I can usually hold my mileage to between 17 and 17.5 daily driving, closer to 18 before a regen cycle kicks in. Now my all-up average is dropping to 17 or so (figure about 300 gallons) and if I keep going on 15-15.5mpg tanks its only going to drop further.

So figure about a 2mpg drop in mileage for identical driving conditions.

I did fill up at a different fuel station, most of the time I go to speedway truck stop and this was a speedway but not my usual big truck stop (10 cents less/gal too, but maybe I got what I paid for?)

Is there any way the fuel filters could cause this? I have not had any messages other than "exhaust filter cleaning". How about the first oil change? I plan to do that soon - I have everything, its just too HOT to go wrenching right now. Maybe tomorrow...

 

Well, I don't have answers but I do have some comments:

1. The engine oil life monitor system on this truck is real and some of us actually trust it and go 7-10,000 miles on the oil, whenever the truck tells us to change it.

2. The PCM/ECM also will tell you when to change the fuel filters.

3. Check your air filter, not the restriction gauge, they are only $12 on this truck, cheap insurance and cheap way to eliminate one MPG Killer.

4. Might want to rotate tires, check pressures. I like the ride when all 4 tires are at 74 PSI.

5. Try using the motor craft fuel additive/ cetane boost. Could be time for this especially since your gut is pointing you towards the fuel. If you filled up with some kind of bio blend which is popular in the mid west it certainly could be the issue.

What does high humidity and high ambient temp do to the engine? I don't know but we are def in the dog days of summer. Could be the ambient air sensors combined with the NOx and 02 sensors running a rich fuel mix?

 

Probably nothing to worry about, I've seen ~2 MPG variances before and thought nothing of it. Joel may have something about the heat though. Have you been using your remote start much?

Complete agree here. Modern oils last a LOT longer than the oils of yore. Ford is making a $15K bet that longer oil changes will do no harm to your engine with this system. They stand nothing to gain if they win, and lots to lose. They wouldn't use a system like this if they weren't confident in it.

Complete DISagree here! The only way you're going to see a MPG loss with a plugged air filter is if there is a serious restriction preventing the engine from getting enough air. That's why we have a restriction gauge, as it actually measures this! IMHO something as subjective as a visual inspection is nowhere near as accurate as the gauge designed to measure such things. Could be nearly black, but if air is still flowing through it there's nothing wrong with it!

[QUOTE=ruschejj5. Try using the motor craft fuel additive/ cetane boost. Could be time for this especially since your gut is pointing you towards the fuel. If you filled up with some kind of bio blend which is popular in the mid west it certainly could be the issue.[/QUOTE]

I always used this product in every tank, and I believe that's why my fuel efficiency was consistently better than most.

Means that there is less O2 going into the engine due to the reduced density caused by heat and displacement caused by the humidity. Which means that most N/A engines simply would make less power in such conditions. I'm willing to bet that these engines can compensate for temp with higher boost to make the same power, which would lower efficiency. Because it would take more boost to make the same power. I think you have something here, Joel!

 

fuel...fuel...fuel...I can easily see 2 mpg difference from tank to tank...in fact, last night I fueled the truck up by my daughters before delivering her truck. I usually see 19 to 20 on the trip computer on this trip...last night it was 22.5. It was 90 degrees outside, climate control set on auto at 72 degrees and 70 mph on the freeway parts of the drive.

I drove Melissa's truck on the way up. It was steady at 19 mpg. Deb was driving our truck and I do not know what she was seeing for mileage. I must say I was nicely surprised by the great fuel mileage.

Regards

 

Thanks for the info.

Rick, I have seen upwards of 21mpg max but thats about the peak. This is with driving 60mph on country roads and no AC. Is the gear ratio in the truck you reference 3.31 by any chance? I have 3.55's and 20" wheels so that may account for part of the difference.

I have not been running my truck in idle much at all. I avoid this at all costs due to past history with EGR and injector issues on the 6.0 and 6.4. Whether or not this is warrented I don't know, but I would like to err on the side of caution. That having been said, however, I usually will use the remote start to fire up the truck before I jump in - it just doesn't sit there and "idle" long before I jump in, maybe 2 minutes at most.

On a side note - my remote start only works about 1/2 of the time. I think it is a range issue more than anything. My aftermarket remote start I had in my 2010 worked a LOT better.

I know the sensors and gauges on the truck are there for a reason, but particularly this first oil change I want to get that done asap. The oil life may still have another 5000 miles in it but I want to flush the engine. My opinion is all the new parts are wearing together and there could be elevated levels of wear material in the oil as a result. I'd feel better getting it flushed out. I am also sending in a sample to Blackstone Labs.

As to the tire rotations - I am tuned in to this. I've read a lot about the tires wearing out (20" michilins). I have been paying attention to the wear of the tread since day 1 and my front tires have started a tad bit of a "wedge" pattern (the level of the lugs is slightly angled). I will be reverting to tire rotations when I do my oil changes.

 

I love the radio humor!

 

I think it could be the fuel also. My brother is a complete mpg freak. He started buying cheaper diesel and his mpg dropped significantely. He sooned realized he couldn't afford cheap diesel. He hand calculates every tank. Noticed up to 4 mpg difference.

 

That may very well be. The tank on my truck is so big I end up running for a good while on it. My driving is also not all identical so by the time I am ready for a fill up I can't correlate the change in mileage too much according to fuel alone.

 

If it were me I would not complane. I only get 13 or 14 mpg, and a lot less when pulling. I have a lot of other issues to deal with until I can check it out.

ken