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You aren't very specific on which type of a roof mounted carrier you are talking about, or what year model/engine setup you have in your Q7, which would inform the members to provide some response that is relevant.
FYI, I have the TDI engine, and just the roof carrier bars alone nets me a loss of 1-2 mpg off my normal average mpg. I took them off yesterday even though I like how they look on the car...not worth the noise and loss of mpg when not in use. I took a picture of them mounted, so I can look at that pic all I want, or even make it into a screensaver, LOL! But they are most definitely not going back on car until I will carrying something on them.
Last edited by '10Q7TDI_Prestige'; May 26, 2022 at 05:23 PM.
You aren't very specific on which type of a roof mounted carrier you are talking about, or what year model/engine setup you have in your Q7, which would inform the members to provide some response that is relevant.
In general, anything added above your roof is highly exposed to wind drag, then there's also the weight added to car when loaded, etc. If you're talking about the cargo box clamshell-type like Audi sells, then yeah, a 15%-20% drop sounds extremely reasonable, as you use a carrier box when your car is fully loaded otherwise + the added drag. If you are talking about a mesh tubular, or wire style cargo roof rack that is basically just a framework or 'shopping cart' on your roof to put stuff in and secure it, then the loss in mpg will depend on how well you load the car and secure the load/streamline it, etc., as well as how it is designed with/without aerodynamics in mind.
I'd start by considering what I need the carrier to do for me: How often will I need to access it? How much weight and what type of items will I be carrying? Am I willing to leave it mounted on the car when not in use? Where will I store it when not in use? Will it interfere with parking my car under cover/in garage, over terrain (campgrounds) etc. How will it affect my mpg/handling/load balance of car? What's the best option for what I need it to do and to make my life/trips easier, not harder?
FYI, I have the TDI engine, and just the roof carrier bars alone nets me a loss of 1-2 mpg off my normal average mpg. I took them off yesterday even though I like how they look on the car...not worth the noise and loss of mpg when not in use. I took a picture of them mounted, so I can look at that pic all I want, or even make it into a screensaver, LOL! But they are most definitely not going back on car until I will carrying something on them.
bc I don’t believe there will be much difference in increased fuel usage between a gasser and diesel… And I doubt I’ll find someone with the same exact model roof rack I’m looking at
I’m just looking for some real world data to see if the 15-20% loss is really true.
But if it helps you , I have a 2013 Stage 2 Malone tuned/deleted TDI and looking at the long slim/more aerodynamic type of cargo boxes vs the bulky brick looking ones.
but will gladly take any real world date from all Q7 owners.
I have a Yakima Rocket Box. Older model very thin and long. It’s more aerodynamic. At Highway speeds , ( 70- 75 mph) I only see about 2 to 3 mpg fuel efficiency loss with it. At current fuel costs, about $2.00 per 100 miles. Pictured on our first TDI Q7 several years ago.
Last edited by J. Patterson; May 30, 2022 at 03:16 AM.
UPDATE: Just read a recent Consumer Reports article (updated 17 June, 2022) on stretching your fuel usage, which covers aero drag from bike carriers/roof bars/roof boxes, as well as quantifying expected loss of mpg at higher highway cruising speeds, etc. It's an interesting one-pager.
Audi Recreates Crazy-Looking Speed Record Breaker From 1935
Slideshow: Audi has recreated one of the wildest machines of the pre-war speed-record era, reviving a streamlined V16 racer that originally exceeded 200 mph in 1935.
Roof Cargo Boxes and MPG loss
