Camper top killed my gas mileage

200lbs shouldn’t lower mpg that bad, full time up like op have mentioned should help

 

I do drive very conservatively because I do a lot of long distances and want to keep my gas expenditures down.

What do you mean by a tuneup?

 

Here’s an example from a trip I did over the summer, just to show I’m not exaggerating. I averaged 24.4mpg over 83 miles. You can see the odometer is the same in both photos. Traffic got bad after that so MPGs dropped below 20 for the next leg of the trip. My speedometer is calibrated and 100% to account for my larger tires.

 

This.....what is a tune up?

there are only a couple things you can do.

make sure your filter is clean.
change spark plugs at the proper interval.
make sure you are running the proper weight oil in engine, trans and diffs. (if its too thick, will decrease mpg)
tire psi.
alignment.

thats it. nothing else to tune up that will affect mpg drastically.

 

I don't buy it. Shell weight is somewhat negated by eliminating the poor aerodynamics of the tailgate. For argument's sake, I'll give you - .5 mpg, max.

 

I don’t remember there being any mpg change when I added my shell last summer.
Maybe something else is going on and it is coincidental to the shell.

 

I'd think the aerodynamics would help improve, or stay steady at current MPG not decrease it.

 

There is an easy way to figure this one out OP! Take the shell off and see if your mpg's return to what you were getting before buying the thing.

I know they are a pain to remove/install, but that will definitely tell you if it's the weight of the shell "tanking" your gas mileage.

 

Maybe your computer is wrong. Start with a full tank reset your tripometer then drive for 200 or so miles and refill the tank and do the math.

 

It ain’t the shell. 200 lbs would have a very minimal effect on mpg. If that was the cause then 2 passengers and 200lbs additional equipment plus shell would put you in single digits mpg. Also figure your mpg the right and accurate way. Fill the tank, drive x number of miles, fill the tank again. Divide gallons used into miles driven = accurate mpg. Do not trust the truck’s electronic calculations. After a couple tank fills and you calculate the mpg accurately then let us know the mpg. If the mpg is still crap then you need to find the real reason for the crap mpg. - dirty MAF, needs tuneup, low tire inflation (I doubt it since the tire pressure unit would light you instrument panel, could be your driving habits or dozens of other things.

 

What Sprig said, do your own math.
I know if I stomp the pedal to get on highway or passing somebody my screen will show low mpg for a long time before it catches up to how I'm driving. Therefore I pay NO attention to what the screen says.

 

I have no cap/shell on my truck and am getting 15.7 mpg now due in part to winter gas blend, freakin' cold temps, and short trips.
Come nice weather and summer blend gas I will easily get 20+ mpg doing the same short trips. I have a '16 long bed with 68,000+ miles on it.

So: winter blend gas, cold temps, trip distances????

 

I get 22 with a stock 23 Sport

 

if you think regular maintenance/tune-up is expensive, just imagine if you had a less reliable vehicle!!

With 63500 miles, you are probably due for spark plugs, engine air filter, oil change and other things… why would you not do the maintenance?

 

OP, This. A full tank ~108 lb reduces your mileage, a nearly empty tank ~6 lb increases your milage. Do a couple complete tank fills and empties till the light goes on, and this will also vary your average driving conditions.

Also, tire pressure. Especially rear. After basic mileage test as described above, change only one variable at a time. You're +200 Lb constant to a ~700 total load capacity. Add a couple PSI above the door stcker spec.

Also, the stock leaf springs are weak as fuck. This will take its toll, and the ass end will start sagging. It probably did a little when you put the cap on. You could remove your cap and measure ride height with a full tank. Then put it back on and measure again. That will give you facts. As the ass sags, so the grill stands prouder, reducing aerodynamics. Trucks are built with rake for a reason. Load it up and the rear end sinks. That plus low tp adds together to increase aerodynamic drag and road friction.

So many things. Ignore the electronic "features" and focus on the physics, is my recommendation.

 

Something is definitely wrong or you do a lot of idling/short trips.

You should be getting 17-19 easily on winter gas.

 

If you think that's bad, try doing this.....

 

Well it’s like having a passenger in your truck. That definitely doesn’t affect MPGs

 

BINGO!

I added a fiberglass topper and Decked system at the same time, and of course immediately saw the sag and felt the bumpstops. At first I thought I was crazy after adding an Icon leaf pack (stage 3), I was thinking my MPG's would be worse. Nope, I noticed on the way home it had not only better highway manners (from not porpoising and bottoming out) but it seemed I no longer felt like I was driving in to the wind,,, the aerodynamics were better with rack back in the truck.
In the end- I suspect the weak rear springs sagging affect aerodynamics more than some may think.
OP's truck isn't sagging as much, but is defiantly showing the affects of the added weight.

OP a 50 mile trip isn't a good test,, run a few tanks with similar situations.

 

I’m getting like 12.5 mpgs