One show on mithbusters had a test with the tailgate down on one and up on the other,useing f-150 thangs,filled the tanks on both ran highway,with speed control on both....supriseeeeeeeeeeeeee...out of fuel first, the one with the tailgate down.

Seems that with the gate up the air hits the back of the gate and creates a vortex which make the air hit the rolling vortex and go over the back of the truck. With the gate down there is no vortex created thus letting the air hit the downed gate causing more drag.

 

I had the same experience with my Ford trucks and a high rise cap. I still own a high rise cap (doesn't fit my Dodge though). When I removed the cap mileage headed back up. I believe there is a turbulence created that could be cured with a spoiler diverting air down the back window of the cap ( like the old station wagons used to have). I never could find one to fit my cap, so I never got a chance to prove my theory.

 

Just a question but what are yall getting on average for a full tank of diesel highway/city auto/6speed.

Not trying to hijack the thread but just trying to make my decision on wether to get an auto/6speed

 

What someone found a way to make a CTD run on cheap GAS? Oh my [sm=escape.gif]

 

Depending on my foot, 575-620 per tank with the auto/3.73 gears.

 

My last three non - towing tanks have been 19.5, 19.3, 19.4 mixed driving, taking it easy.

 

Now that the weather is changing,mine will go down due to having to warm up three gallons of oil in the morning.
Some where around 17.4 combo of city hwy.
monday leaving for 650 mile each way trip,just a reminder my Ram hangs arourd 2000 rpms on the road,but when its go time,plenty of punch left.

 

I must have something wrong with my cummings. Understand this is my first Oiler. I've been stuck on Chevy gasser for the past decade, and just upgraded two months ago. I have WAY Too much black smoke, and hand calculated MPG is less than 17 with 90% highway, flat road, no wind, and no towing? Any ideas before taking it to the shop? I just bought a used 2006 Ram 2500 CTD 4X4 QC, Bullydog w/ outlook, Air-Raid intake, 4" Cat-Back no topper or cover, current odometer reading 21,560 miles. I thought these things are suppose to run more efficient than gasser? I'm in the south, and run Low-Sulphur. I don't dog on it, and tried multiple settings on bullydog (Stock vs. 75%/Performance settings).????????????

 

First off it's a CUMMINS, loose the "g".

I have read that intake and exhaust mods will lower MPG, I'm all stock. How much air do you run in the tires? I run 70# rear, 65# front. At what speeds are you running on the highway? At 60 my mileage gets better, at 65 it holds where it is, at 70 it starts going backwards, at 75+ it drops like a rock. Are your air and fuel filters clean? Are you getting good quality fuel? All these things have an effect on mileage. Then the biggy how hard you stick the pedal when you take off.

 

Pardon the spelling, but intake is clean, oil just changed, not sure on Air Pressure, but I do run 315/70/17 BFG AT. I normally stay around 70mph, but here in Texas Speed limit on Highway is 70, so that equals 75mph in my book. I have the Bullydog with outlook to adjust for tires, so running at 75mph I'm still below 2K RPM. Fuel is Low Sulphur from the local Gas pump, so no mom/pop gas up shop diesel. I'll have to check on the fuel filter, it only has 21K miles, and I don't know when it should be changed, and probably more important what to replace stock/factory filter with?