Tailgate on or off?

[bob k 2]

I was just wondering.

I just drove up to Maine from NJ took 7 hours and had a load of stuff in the bed (moving up here to retire) truck drove great and smooth.

now for the trip back the bed will be empty and no cover.

i was wondering if taking the tailgate off and laying it in the bed would make a difference on drag or gas milage on the way back?

just one of the things you think about on a long drive..while avoiding phone talkers and texters..lol

 

[swshawaii]

 

[Mark K 2]

I just found out that I've been driving illegally in Minnesota for 13 years. It's apparently illegal to drive with the tailgate down for any reason. I wonder if that includes the times I use the bed extender.

 

[EddieS'04]

Mark,

Maybe they let it go as long as the bed is loaded. Otherwise I would think the extenders would be banded for sale in your state. We all know Cali. is that way. If it is against their laws'. Many aftermarket products are baned there, when it comes to auto's.

Many online aftermarkets wont ship baned items to cali'....

 

[Richard L]

The Mythbusters TV show proved that driving a newer pickup truck with the tailgate up gave better gas mileage than with the tailgate down or removed.



The did a kind of wind-tunnel test with a small scale model truck in a tank of flowing water. When they added some small visible particles to the water, you could see the flow was creating a circulating bubble in the truck bed that caused the air to just pass over the bed and tail gate. With the tail gate down, there was just turbulance that created drag.



They also test drove two trucks, one with the tail gate up and the other one down. Each truck contained exactly the same measured amount of gas. On a road trip in normal traffic, the truck with the tail gate up got better mileage and went further on the same amount of gas.



...Rich

 

[Jerry Abson 3]

Mythbusters was right. I went from Maple Valley WA to Ocean Shores for some work. Before leaving, wanted to test that (before mythbusters) so filled the tank and dropped the tail. When I got to Ocean Shores, hit a gas station and filled up and recorded mileage. Then, when it was time to go back home. filled up again at same gas station (at Ocean Shores) and then headed home with tailgate up. Stopped at the Maple Valley gas station and filled up and recorded mileage.



Don't remember the exact number, but it was significant! I want to say went from 17 to 15 MPG, but knew from that day on, either my tails up or I am staying home!

 

[Richard L]

Jerrya,



I don't think your test was very scientific since going back an forth between two locations can often yield different MPG readings. This is often caused because of a lot of factors not included or excluded for the return trip. Wind direction, wind speed, elevation changes, traffic conditions, weather, temperature, etc. They all effect gas mileage. In your case you were going to the ocean shore which is lower in elevation, so your trip back to Maple Valley was uphill and that had some effect on your mileage.



In the case of the MythBuster's test, they drove identical Ford trucks, in the same direction, in the same traffic, at the same time. So that rules out wind, weather, temperature, traffic and elevation differences. The only difference was that one truck had the tailgate up, and the other had the tailgate down.



...Rich

 

[Jackson Ellis]

For mpg tests that you conduct on your own, there is another big factor that can affect your math; that meter on the gas pump. They can be horribly inaccurate. I have a 14 gallon gas caddy that I fill up to the exact same point each time i get fuel in it. Sometimes it's a little above 14 gallons, sometimes a little below. Once it was only 13.3 gallons, which could save me several bucks if I could consistently get the same pump to short-change itself, but that's not even reliable. I'd say that the pumps could be wrong on either side by about 5% for a possible 10% difference between two fill-ups. 10% is at least 1.5 mpg in these trucks. I wouldn't trust the ST trip computer any more than that either; it's calculating miles driven and fuel volume used, which both have more room for error. Plus, I believe most trip computers have a "glass half full" attitude!



For complete accuracy, you'd have to measure out exact volumes of fuel and add them to your ST after draining the fuel tank, drive the exact same route using mileage markers or GPS (rather than your odometer), and match the weather, traffic, and other factors mentioned above as closely as possible. Then drain the fuel back out and measure how much was used.



So why don't we get huge swings in mpg indicated with all these error potentials? Statistically speaking, when you have a large number of sources of error, they tend to cancel each other out instead of stacking up high or low. But take a 1000 mpg measurements under exact circumstances, and you'll get a least a few high and low measurements that make you shake your head.

 

[Richard L]

ncstatewolfpacker,

You are correct that pump accuracy can very, but most states regulate pump accuracy and require occasional inspections...especially if they get complaints that a gas station might have some inaccurate pump meters. Some stations have been found rigging their pumps with a switch that allows the station operator to remotely control switch the pump pump less gas, but show that more gas was pumped. It has happened but they are rare incidents.



Most people do not have a gas caddy to get precise fuel measurements, and that is not really that necessary for the average person to get a reasonably accurate MPG calculation.



The important part of checking gas mileage is to use the same pump to eliminate any cumulative over/under meter readings errors that might existe between different pumps.



The other critical factor to accurate mileage calculations is to not round the meter reading or the odometer reading. That means if the pump says you pumped 10.12 gallons, don't just round it to 10 gallons. The goes to odometer readings...don't round off the tenths of a mile.



The other most important thing to NOT do, is to use the Gas Gauge to calculate gas mileage. Anytime I hear someone start complaining about their gas mileage using the distance traveled on a Tankful of gas??? The odometed is not that accurate, and the gas gauge is even more inaccurate. Also, consider that you can often slowly pump 2-3 gallons more into the tank than the tank is designed to hold. People often pump 22-23 gallons into a 21 gallon tank which should not be possible. Also gas expands and contracts with temperature changes which changes the gas gauge readings. That's like trying to calculate the number of teaspoons of water in an Olympic sized swimming pool.....That is just a wild-ass guess.



...Rich