This may be way off base but i have found a trend in this thread.
If i can believe everyone is trying to tell the truth about milage,it seems most who are reporting 12 to 14 mpg are Lariat owners and those that are reporting very high or very low readings have fx4 or other models.The difference is Lariat has a trip computer which is quite accurate as it does not just measure gallons into miles traveled.The other method can be a real fooler if a small mistake is made.

Mike

 

Last week, I leadfooted it back to Maryland from South Florida while towing this:



75-80 mph the whole way.

12.5 mpg for 1051 miles with a 4500 lb. boat in tow.

Something just ain't right with that pretty Yellow Screw. Don't give up on her yet.

 

YellowFX4Screw,

I have put 7000 mi on my truck already!!!

I live in Chico, CA where I think we use Ca winter gas. I always fill up a Chevron, not usually at the same station. The temp here is 30-50 in the winter.

I have an 04 Screw 4x4 5.4 with a 3.73 lsd

For the first 5K I was getting city/highway 15/17 mpg and I don't drive easy. I changed my oil to mobil 1 syn 5w-30 thinking it was the right oil (stock is 5w-20 syn). Now I am getting 13/15 mpg. Needless to say I'm going to use the right oil next time!

The sticker on my truck quotes 14/18 mpg. In smaller print it says the EPA reports show 11-17/15-21 mpg. I'm sure anything within 10% is normal.

If your numbers are correct then you got a problem! Your warranty should cover this. Do not trade in your truck! Your dealer is being a pain in the a$$. You either need to put your foot down with the service manager or you need to go to another dealer. Imo they need to fix the problem. Also there are lemon laws that will ensure that they fix it.

Hang in there

 

Is it possible that your speedometer/odometer is off? If so, any type of calculation is suspect.

I would try to verify that it's accurate before going any further.

 

It won't make up the difference, but the front push bar on your truck is a wind trap. Wind resistance increases exponentially with speed so it is a much bigger problem at 65 than 55 mph. It does not explain such low numbers, especially the city driving, but it might help if you are so desperate to get an mpg increase. Maybe it is a combination of factors (wind resistance, cold air, bad gas, odometer problem, ethanol?, etc). Good luck. I would hate to see you take a loss on a trade in of thousands of dollars. It would take several years to make up the difference in gas savings unless you buy a Civic.