[CROSS CANADA WITH 8]

Thanks to all of you for your helpful suggestions.

I went out today and did a fairly controlled test with the car top carrier on at various speeds, and then off at exactly the same speeds. I thought you would all be interested to hear the results.

It was about 50 degrees, cloudy, with no rain and lower than average wind (for NS). I had to drive to the testing area, so I was able to fully heat up the engine before I began. I drove between two exits that are about 7 miles apart. I set my cruise (which stays dead on) at a starting point and never touched the gas or the brake once until I reached the ending point. Then I turned around at the exit and did the same thing in the other direction (getting a very consistently different result because the return trip was uphill). Then I averaged to get a round trip result.

Here are the results:

Average MPG.

Speed -----Without ----- With --- Percent
----------- Carrier ----- Carrier --- Change
60 mph --- 35.4 mpg -- 32.2 mpg -- 9.0%
65 mph
70 mph --------------- 27.5 mpg
75 mph --- 28.25 mpg - 25.3 mpg---10.4%

Comments:
1. As you would expect, at higher speeds, the
carrier has a greater effect at higher speeds.
2. Speed is a bigger factor than the carrier.
- Slow 15 mph w/out carrier improves mpg 20.0%
- Slow 15 mph with carrier improves mpg 21.4%
- Slow 5 mph with carrier improves mpg 8.0%

Cost for 10,000 miles with gas at $3.25/gallon

Speed -- Carrier -- MPG -- Gallons -- Cost
- 75 ----- Yes ---- 25.3 --- 395 --- $1284
- 70 ----- Yes ---- 27.5 --- 363 --- $1180
- 60 ----- Yes ---- 32.2 --- 310 --- $1007
- 75 ------ No ---- 28.25 -- 353 --- $1147
- 60 ------ No ---- 35.4 --- 282 --- $916


So…
What difference does it make to remove the carrier?
- At 75 mph, it saves $137
- At 60 mph, it saves $91

What difference does it make to cut speed if I use the carrier?
- Cut speed from 75 to 70 mph; save $104
- Cut speed from 75 to 60 mph; save $277

What difference does it make to cut speed if I am not using a carrier?
- Cut speed from 75 to 60mph, save $231

What difference does it make to cut speed and to remove the carrier?
- Remove carrier and cut speed from 75 to 60mph; save $368
- Remove carrier and cut speed from 75 to 70mph; save $230*

*The last of these is a reasonable estimate as 70 with no carrier was never measured.