Americas Why all the fuss about fuel economy?

[LeeroyJ]

I'm extremely skeptical about both the mileage reported by the onboard computer, and the mileage reported by people on this and other forums. If you add anything that negatively impacts airflow or adds weight, you are likely negatively impacting your fuel economy. A roof rack, roof top tent, lift, larger and/or wider tires, MT's instead of AT tires, external moley panels, bull bar, extra lights, sidesteps/sliders, etc. etc., they all impact MPG negatively. Your average speed for a trip will also impact MPG, in an exponential fashion (or at least not linear). Add a headwind, climbing altitude, colder temps, etc., and there can be some major differences in one drive to the next even if you haven't changed anything on the vehicle itself.

All that being said, I wouldn't expect an impact of 30% for adding a low-profile roof rack. You need more data.

In addition, the only accurate way to measure MPG is to first fill the Grenadier and record the mileage. Then drive. When you fill up again, you know accurately how many gallons you used and you can subtract the new mileage to figure out how far you drove. In my experience my real economy has been substantially less than what the computer shows me getting.

This is why for me, the Longranger extended fuel tank is my most important mod.

 

[Zimm]

I am looking for feedback on what kind of a fuel economy hit folks have taken from mounting different kinds of roof racks.

I mounted four INEOS Grenadier: DualTrack™ Low-Profile Roof Rails from DVAmechanics on Saturday and then drove about 120 miles yesterday, most of that distance at 70 to 75 mph. The fuel economy appeared to be reduced by approximately 30% (I will start a more controlled test when we hit the road again tomorrow). This probably explains why the onboard software caused the fuel bong to go off when I had only used 15 gallons (usually it goes off closer to 19 or 20 gallons down). (I filled the tank yesterday to confirm how far down the fuel level was.)

I didn't buy a Grenadier to save the planet and gasoline is cheap, but even with those givens I am not happy with what appears to be a dramatic reduction in range (something which appears to far outstrip my ability to compensate with the rear mounted jerry can support I am trying to figure out how to install).

I really want to believe my problems are caused by something else; I had not driven the truck more than a very few miles since having my 20,000 mile (second) service check at my dealer a week ago so I am desperately hoping it's their error. For what it's worth, the roof rails are really quite elegant. They have an extremely low profile (3/4 inch height increase) and seem to be incredibly adaptable. While my arthritic hands could have done without the tighening (and loosening and retightening) of 64 different sized hex screws, the overall product fits well, looks good, and appears to be almost infinitely adaptable -- it's also eminently affordable if you're willing to do your own assembly. But this isn't a snap on / snap off design: removing the four bars (even without disassembling them) will require removing 32 of those hex nuts and (for this old man) a good hunk of time.

My fuel economy was a pretty consistent 14 to 15 miles per US gallon before I mounted the roof rack. I should have a more precise sense in a couple of days what it is now.

You realize, even if your number is solid, which it isn't, but let's just say it is, this has NOTHING to do with the grenadier. The shitty aerodynamics of roof rails and whatnot, do not impact any car any more than any other car the same product is put upon.

 

[Guvnor]

I'm extremely skeptical about both the mileage reported by the onboard computer, and the mileage reported by people on this and other forums. If you add anything that negatively impacts airflow or adds weight, you are likely negatively impacting your fuel economy. A roof rack, roof top tent, lift, larger and/or wider tires, MT's instead of AT tires, external moley panels, bull bar, extra lights, sidesteps/sliders, etc. etc., they all impact MPG negatively. Your average speed for a trip will also impact MPG, in an exponential fashion (or at least not linear). Add a headwind, climbing altitude, colder temps, etc., and there can be some major differences in one drive to the next even if you haven't changed anything on the vehicle itself.

All that being said, I wouldn't expect an impact of 30% for adding a low-profile roof rack. You need more data.

In addition, the only accurate way to measure MPG is to first fill the Grenadier and record the mileage. Then drive. When you fill up again, you know accurately how many gallons you used and you can subtract the new mileage to figure out how far you drove. In my experience my real economy has been substantially less than what the computer shows me getting.

This is why for me, the Longranger extended fuel tank is my most important mod.

Don’t forget the trip computer is showing MPG in IMPERIAL gallons NOT US gallons that are approximately 20% larger. Do the maths and you’ll find it’s more or less 15 MPG as declared by Ineos.

 

[Zimm]

Don’t forget the trip computer is showing MPG in IMPERIAL gallons NOT US gallons that are approximately 20% larger. Do the maths and you’ll find it’s more or less 15 MPG as declared by Ineos.

US trucks are set to US gallons not imperial.

 

[Tenac]

US trucks are set to US gallons not imperial.

I would hope so or that is some half A$$ stuff. lol

 

[LabRat]

US trucks are set to US gallons not imperial.

You sure about that? The + and - for cruise control certainly isn't in MPH.