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  #1  
Old 08-03-2014, 11:42 AM
1985 190d
 
Join Date: Nov 2006
Location: canadian border vermont
Posts: 481
Could I lose 8mpg with a bike rack?

Just back from a trip to Maine. 5 hours across on secondary roads, mostly under 60 and a lot under 50. A/C on the whole time. Really a great trip for a 30yo car as the likeihood of getting trapped in standing traffic is nil, and anyway, who wants to sit in a Honda Fit for 5 hours one way?

We were three grownups, with luggage (so heavily freighted) and with a rear mounted bike rack hanging off the trunk. My mileage appeared to be around 27mpg. I have never gotten mileage so low-- its usually around 34-35.

Just how much drag is a bike rack anyway? Should I charge my wife extra?
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  #2  
Old 08-03-2014, 11:59 AM
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I don't think the bike rack is the culprit. You've cited many factors which reduce mileage. Were you going up and down a lot of hills as well?

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'95 E300D, 425K
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  #3  
Old 08-03-2014, 12:00 PM
funola's Avatar
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Did a fuel leak develop on the trip?
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  #4  
Old 08-03-2014, 12:09 PM
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I don't know how well it translates but I have heard that every 100-150 lbs added tends to take 1mpg off, so with 4 adults and their luggage I'd hardly be surprised at that mileage. With my roof rack I lose about 2mpg on the highway.
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  #5  
Old 08-03-2014, 12:15 PM
1985 190d
 
Join Date: Nov 2006
Location: canadian border vermont
Posts: 481
Doubtful on the fuel leak since no odor of fuel and I have both belly pans installed.

But lots of hills, lots of downshifting.

Im usually careful about not resetting the trip od but some kind of record keeping malfunction may be to blame. I also had to refill with a truck nozzle and the display on the pump was unreadable. I had to accept the credit card receipt as gospel.

But a bike sideways to the wind cant be good for mileage.
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  #6  
Old 08-03-2014, 12:31 PM
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FYI When driving from KY to FL in my 87 300SDL I get 30 mpg with no bike rack and 22 mpg with rack with three bikes - all other things being equal. This is 70 mph on (almost) all interstate. I assume wind resistance. It's surprising. This car gets 25 overall.
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  #7  
Old 08-03-2014, 12:50 PM
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Top Gear did a show on wind resistance. I wish I could recall the two cities they cited but the overall premise was that you would save money by having a bicycle shipped by rail rather than by using a bike rack.

Mercedes designed a very aerodynamic car after the Box Fish.

It has a very low drag coefficient, I want one.

The extra weight will also reduce your MPGs and might have made you nose high, tail low increasing wind resistance.

Sounds like the trip was fun and should be done again without the bicycle rack. Report your results back
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  #8  
Old 08-03-2014, 01:05 PM
t walgamuth's Avatar
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I would put it mostly to the bike rack. Weight is not much of a factor on the highway and could even increase it by lowering the car.
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  #9  
Old 08-03-2014, 02:35 PM
1985 190d
 
Join Date: Nov 2006
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Quote:
Originally Posted by Ancient Benz Guy View Post
FYI When driving from KY to FL in my 87 300SDL I get 30 mpg with no bike rack and 22 mpg with rack with three bikes - all other things being equal. This is 70 mph on (almost) all interstate. I assume wind resistance. It's surprising. This car gets 25 overall.

That's my 8 mpg on the nose. And your experience eliminates major variables. Roof rack or rear rack?

Since I have full body pans I dont think wind resistance is much altered. But trust me-- with 76 hp at your full command, you can tell when there is one extra person in the car, let alone two!

I was treated well in Me: At one point we parked along the road to hike into the woods and when we returned there was a message on the car from someone:
"If you are broken down, call me-- I am a Benz owner too! If not, nice car!"

I called and turned him onto peachparts. He had a 59 ponton, a 300sdl, and a 240d.

Last edited by vtmbz; 08-03-2014 at 02:42 PM. Reason: addl info
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  #10  
Old 08-03-2014, 02:59 PM
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My coworker would routinely lose 8-10mpg by having his kayaks on the roof of his Subaru and a couple bikes on a carrier on the back....
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  #11  
Old 08-03-2014, 03:00 PM
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Quote:
Originally Posted by t walgamuth View Post
I would put it mostly to the bike rack. Weight is not much of a factor on the highway and could even increase it by lowering the car.
X 2

It's the bike rack.
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  #12  
Old 08-03-2014, 03:03 PM
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Mine is a rear rack. Also, I forgot to mention that this happened more than once.
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  #13  
Old 08-03-2014, 03:14 PM
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A rear rack will cause drag too because it interrupts the flow of air off the rear of the car and can create a suction.
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'15 GLK250 Bluetec 72k - mine - (OC-75,000)
'89 420SEL 166k - mine (OC-167,000)
'01 E320 Wagon - 157k - mine (OC-160,000)
'17 Metris(VITO!) - 5k - wifes (OC-10k)
'01 E320 - 166k - Dad's (OC-165,500)
'07 E350 Wagon - 127k - dad's (OC-126,500)
'01 SL500 - 47k - dad's (OC-47,000)
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  #14  
Old 08-03-2014, 03:18 PM
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Quote:
Originally Posted by t walgamuth View Post
I would put it mostly to the bike rack. Weight is not much of a factor on the highway and could even increase it by lowering the car.

I don't think it should be discounted if the drive was lots of hills and up shifting as the OP mentioned. It's likely a combination of both.
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  #15  
Old 08-03-2014, 03:46 PM
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I've never found hills to affect mileage much. you pull them and then coast down the other side.
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