| Notes From a X-Country Trip
- Click HERE for Original Thread
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| mccvii |
Last week I took the X out for a road trip from Central TX to the Florida panhandle. Here are some results for your enjoyment.
Car was loaded with 5 average sized people ranging in weight from 105 - 180 lbs and associated baggage / accessories for a week trip. All luggage was stored inside the vehicle for the outbound leg of the journey.
The road from TX to FL is mainly flat aside from the occasional rolling hill. AC was blowing between 65 - 70 the entire trip; cruise control kept the car 75-78mph (where possible). We hit minimal traffic along the way so we we able to maintain steady speeds.
I decided to rotate between 87 & 93 every other visit to the pump. Shell & Mobile are my first & second choices. There was a slight MPG improvement using 93 vs. 87. The 93 average as reported by the trip computer was 23.3 while the 87 ran at 23.1. I was able to test this over a couple of refills and the results remained very similar regardless of grade. I was very pleased with the overall economy of the fuel given the extra weight the vehicle was carrying.
On the return trip I decided to purchase a roof mounted cargo container to help us transport the 'stuff' we had acquired along the way. I found a 20 cf model of carrier that mounted directly onto the factory MDX roof rails. I loaded the carrier with most of our luggage and left the cabin for our spoils.
As you might expect, the cargo carrier drastically cut into fuel economy... What I hadn't expected was the impact the the various fuel types would have on the fuel economy. The first tankfull of 93 octane averaged 17.6 MPG @ 70-75mph set by cruise control. The second fill with 87 octane returned a whopping 15.7!!! Similar conditions, minimal traffic, mostly flat, 70-75mph managed by cruise control. I figured it had to be a fluke so I selected the same 87 octane at the next fill. This leg of the trip was late afternoon & early evening so we required less AC to keep cool. Again, the 87 averaged 16.2 as reported by the nav computer. To verify, I had taken note of the mileage at each refill and my manual calculations did seem to correspond to the nav computers calculations with little variation. The next morning I still had a about 1/4 tank of 87 left so I ran it out and refilled with 93. The 93 returned 17.4 MPG for the next tank. Since I can't leave well enough alone and because I like annoying my wife... I decided to try a partial fill with each as I met the last couple hundred miles of my journey. The first stop I put in $10 worth of 87 and saw 15.8. I put in $10 of 93 and recorded 17.4.
I am convinced that this is not coincidence. Oddly enough... I recall my sales person tell me that he always used 93 octane except when pulling his boat. My experience seemed to indicate the opposite. I gather from this experience, the VTEC engine prefers the higher octane when carrying a load. I do believe that I felt less strain while climbing with the 93 vs. the 87. The tach reflected my feelings as it indicated engine speed at various points of the climb. The car did seem to control speed with much less effort while running the 93 fuel with the added aerodynamic load.
I calculated that based upon a 1.5 MPG increase, the full tank of 93 octane would return about 29 (19.2 * 1.5) additional miles more than a tank of 87 octane. 87 Octane gas sold for about $1.75/g with 93 coming about $.20 higher.
At these prices, a full tank of 87 would sell for $33.60 with a full tank of 93 selling at $37.44 for a delta of $3.84 per tank.
Recalling the 29 mile increase with the 93 octane and the 16mpg average noted with the 87, it would take about 1.75 gallons more of the 87 octane to travel the same distance. At $1.75 /gallon, 1.75 gallon of 87 fuel would cost $3.06.
So... At the end of the day, the cost savings of burning 87 gas vs. 93 in an MDX with a over the roof cargo container and 5 adults was about $.80 per tank. quod erat demonstrandum...
Gee, that was fun!
*Disclaimer - these results are unique to me and may not reflect variables introduced in other environments or under dis-similar conditions; ergo... Individual results may vary! |
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| eurohazard |
That is an awesome post........you are more anal than I am. And I mean that in a good way! Haha.
It does make sense that the MDX's good gas mileage,when compared to other SUV's, is because of it's low coefficient of drag. Adding a top carrier increases the drag massively. Still many SUV owners would kill to get 17 MPG at those speeds with 5 people in the vehicle. |
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