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Discussion Starter · #1 ·
I am in the process of doing my test runs with the MDX because the inevitable happened where now I literally have to commute to Miami twice a week, for 16 weeks, which adds like a nice 16k highway miles. Just like the abuse and things my 2016 Nissan Rogue SL went through and had ZERO parts break, the MDX will endure the same testings, but of course, my OCD will kill me and I always keep up to date with maintenance. My current goal right now is to hit 500 miles on a single tank. Not sure how many of you has driven on both the Northbound and Southbound of the Florida's Turnpike, but for those that did, you would have noticed the Northbound is more efficient than the southbound. Also, I do acknowledge not all of us has the luxury to drive at a constant speed of 60 or have the patients to do it either. Under my testing, the variables that I can control are set to the following:

Fuel: Costco's 87 octane
Speed: 60 MPH (minimum speed in most areas w/ posted 70 MPH is 55 MPH)
Tire pressures (warm): 38 psi front, 36/37 psi rear
IDS mode: Sport
Gear: Sport mode set at 9th gear (highest for 3rd gens)
Regular cruise control ON; ACC not engaged.
Lane used: Rightmost lane (the travel lane); I ain't no karen who decides its all ight to hog up the middle lanes and left lane.
Tires: Goodyear Assurance MaxLife @ OEM specs

The range that the MDX was showing me last night was 540 miles. However, there were times the MDX showed me a range of 570 miles. Here are some data points from the live readings via the on-board computer and hand calculations:

Orlando Costco to North Miami Beach Costco:
Miles driven: 267
Miles remaining: 226
Average MPG: 28.3
Highest Average MPG on-board: 29.6 MPG
Fuel tank level: 10.068 gals remaining (based on Edmond's reference of a 19.5 gal fuel tank capacity)

North Miami Beach Costco to home (Orlando):
Miles remaining: 299 (pulled from Acuralink App)
Fuel tank level: TBA (will edit later on)
Highest Average MPG on-board: 33
Fuel level: ~ Half tank (pulled from Acuralink App)

What I don't understand since its literally the same route and road to and from Miami, why is there a discrepancy in the MPGs between both ways even though Northbound has more up-hills? If we have any engineers on board here, please explain why this occurs.

A little side note: From Edmond's website, they showed the MDX achieved 507 miles on the highway for AWD, 526 miles on highway for FWD. This is based off of the Tech package from the 2017 MDX MY. Sport Hybrid, not so much. So my data should match up to Edmond's data, IF everything works out as expected.
 

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I would also keep track of the outside temps. Around 70 degrees is the sweet spot of not needing A/C or heater(s) for max efficiency. I would also gas up the same way from the same stations of fill until "click" and maybe 1 or 2 trigger pulls until click. I would also do hand calculations instead of using the M.I.D.

I'm also want to hit the 500 mile club in my hybrid. Very difficult to do in NM with speed limits of +75 mph and elevations of 4000-8000 feet in a few hours of driving.
 

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on our last trip in our 2019 mdx hybrid one section was going over the continental divide, going westbound then two more mountain passes, speed limit varied from 80 down to 70, Made 462 miles before the "low fuel" light came on, 7 miles shy of where we were staying for the night. filled up with 17.4 gallons, 2 gallons shy of empty. 26.5 mpg. Could I have made 500? probably not but pretty close. I suspect if I had held speeds down to 70 or less it would have been highly likely. to hit 500 on say 1 gallon left= just over 27 mpg. Now the same trip in my duramax truck, no problem, going westbound our stop for the day is at 600 miles and that's where I fill with fuel because the next fuel stop is another 120 miles. But then 36 gallon tank @ 18-19mpg give nice range. Best I ever have done with the truck was when DW was driving the truck following me driving a Uhaul going 60 the whole way. 750 miles and the truck still hadn't hit the low fuel light. averaged 24mpg on that trip. Not bad for a 7500lb barn door going down the road. Uhaul took mulitple stops and used 65 gallons of gas. 11.5mpg.

Now all that said, if one can make 500 miles once, does NOT mean one can make it again on the same route again or on a different route. There are just to many variables that affect mileage. I pretty much assume that based on our driving I need to have a spot to fill by 400 miles on the highway and about the same in town. Once i get close to those distances I can decide when and wear to fill up.
 

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What I don't understand since its literally the same route and road to and from Miami, why is there a discrepancy in the MPGs between both ways even though Northbound has more up-hills? If we have any engineers on board here, please explain why this occurs.
There is more to this than tire pressures, constant speed, and inclines, although those are among the factors that have the most significant impact on efficiency. Other things like drafting can contribute largely, too. Who knows, maybe driving uphill in 9th gear is actually less efficient than doing the same grade in 8th. Outside of the things you can control, there is too much variability around you that you may not notice having an effect.
In an uncontrolled environment spanning 250+ miles, the conditions are constantly changing. A head wind or tail wind of 1mph can have significant influence over a distance that long. Assuming you have zero wind (impossible), changes in temperature and humidity contribute to aerodynamic drag and combustion efficiency.

Looking at the equation for drag: D = Cd * A * .5 * r * V^2
In your tests Cd, A, and V remain constant, so the drag on the MDX changes based on the density of the air. Air is less dense at higher temperature, and is less dense at higher humidity (molar mass of water vapor is LESS than that of air).
In reality, the slight changes in density due to temperature and humidity will be less noticeable than reducing velocity by 1mph because the velocity is squared.

Engines on the other hand perform better in cold, dry conditions. Cold air is more dense than warm air per unit volume therefore it has more potential energy to give during the combustion cycle. More oxygen = more power for the same given stroke. If the air is humid, some portion of that volume is occupied by water molecules rather than air. Because water has higher heat capacity, the water vapor acts as a heat sink, absorbing more energy from the combustion and reducing in-cylinder pressure. More water in the air = less power in the stroke.
More reading on engine parameters to consider:

We can open up a whole can of worms and break down each possible scenario mathematically but it's not worth anyone's time. These are just two examples I can think of but how significantly they actually influence your observed efficiency would be nearly impossible to determine considering how variable the environment is and how many assumptions would need to be made regarding the engine performance.
 

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Someone has too much time on their hands. As has been stated, too many variables. Daytime driving vs nighttime driving? Cooler at night.
 

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Discussion Starter · #7 ·
500 is doable. Still have at least 4 gallons left. Max range according to the MDX is 570 miles. I can confirm this once I fill up after class.

Someone has too much time on their hands.
More like last minute change from online to in-person, with a 250 mile commute one-way.
 

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Discussion Starter · #8 ·
My MDX has dethrown my record holding 2016 Nissan Rogue SL fwd at 520 miles. Now at first place with 526 miles with 17 gals used. Idiot lights popped up while I was literally pulling into Costco.


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If you want record fuel economy would you not use comfort mode in drive? Looks like you’re doing pretty good as it is.

As to different fuel economies each way, roadway surface roughness would also have an impact. Portland Cement Concrete vs Asphaltic Concrete as well as jointed vs continually reinforced PCC.

Since you’re in Florida, I presume the departure and destination locations are roughy the same elevation (say within 100 feet elevation of each other)? Over here on the left coast when I travel a couple hundred miles from sea level to about 4000 feet on the high desert I’ll get lower fuel economy one way vs the other due to the elevation difference (amount of work the engine has to do, work being a force over a distance). Average air density over the trip each way presumed to be about the same.
 

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Discussion Starter · #10 ·
If you want record fuel economy would you not use comfort mode in drive? Looks like you’re doing pretty good as it is.

As to different fuel economies each way, roadway surface roughness would also have an impact. Portland Cement Concrete vs Asphaltic Concrete as well as jointed vs continually reinforced PCC.

Since you’re in Florida, I presume the departure and destination locations are roughy the same elevation (say within 100 feet elevation of each other)? Over here on the left coast when I travel a couple hundred miles from sea level to about 4000 feet on the high desert I’ll get lower fuel economy one way vs the other due to the elevation difference (amount of work the engine has to do, work being a force over a distance). Average air density over the trip each way presumed to be about the same.
Elevation isn't consistent within the state. However, I can only replicate this on FL Turnpike. Not on I-95, I-75, US-27, US-41. I believe it has to do something related to the characteristic of each major road. That 520 miles was also achieved on the Turnpike too.

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Discussion Starter · #11 ·
I think my MDX is now challenging me. 600 miles???

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Gas is cheap there. Just wondering what would happen if you ran into a traffic jam? There is a reason it’s called an idiot light.
 

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Discussion Starter · #13 ·
Gas is cheap there. Just wondering what would happen if you ran into a traffic jam? There is a reason it’s called an idiot light.
I actually did ran into a traffic jam on the Palmetto expressway (only highway other than 75 and 95 that isn't a full blown toll road). My range did drop a little bit. Now if I had been in a traffic jam when those lights turned on, I would actually exit off and find the nearest shell or Wawa.

Orlando area Costco is 10 cents cheaper.

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my experience from 30K miles is that at least on my 2019 hybrid the mpg readout is optimistic, usually by at least 0.5mpg, and hence the range is optimistic as well. And do you REALLY want ti run the car to completely empty? low fuel comes on with 2 gallons left= approx 40-50 miles.
 

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It is good to know you have around 2-3 gals in reserve with DTE under 35 miles. My 11 MDX had a 20 gal gas tank; but, it would take 23 gallons if I wanted to top it off. I did that once to see how big the fuel tank+reserve was with my 11 MDX DTE under 10 miles.
 

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Discussion Starter · #16 ·
Just did my hand calculations, and there is a 1.3 MPG difference. Not much of an issue, but I'm glad that I still hit over 30 MPGs in this tank. However, I will attempt a 2nd run later on, but with using 93 octane, and from Costco (unless Shell lowers their prices).

It is good to know you have around 2-3 gals in reserve with DTE under 35 miles. My 11 MDX had a 20 gal gas tank; but, it would take 23 gallons if I wanted to top it off. I did that once to see how big the fuel tank+reserve was with my 11 MDX DTE under 10 miles.
Reserve for the 3rd gens is like 1 gal? At 18 gals, the needle is literally near that red E line or more like the bottom part of that needle is touch that red line.

my experience from 30K miles is that at least on my 2019 hybrid the mpg readout is optimistic, usually by at least 0.5mpg, and hence the range is optimistic as well. And do you REALLY want ti run the car to completely empty? low fuel comes on with 2 gallons left= approx 40-50 miles.
I haven't ran the MDX below 1 gal remaining yet and I don't have plans to do that. I did ran my 2016 Rogue constantly to empty and that vehicle's fuel pump didn't gave out at all. I lost track of count on how many times I let that tank get down to 0.1 gals remaining. I can say, modern cars can take abuse well but if the owner doesn't maintain the vehicle, then obviously things will fail.
 

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Elevation isn't consistent within the state.
Elevation in Florida is extremely consistent, more so than anywhere else I can think of, and it's consistently hovering close to sea level, which means high air density compared to higher altitudes, which means more efficiency and power. The highest natural point in Florida is only 345 feet. I routinely climb higher than that just on my daily hikes around here (San Diego).
 

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I go from 4900 feet from my house near the Rio Grande to +7000 feet in the 35 min drive to my in-laws in the foothills in ABQ.
 

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Discussion Starter · #19 ·
Ight. Ya boii doin the run again, but with 93 octane. Initial observations... no difference than the run on 87 octane.

Tire pressures: 36 psi fronts, 35 psi rears.

Route: Florida's turnpike

Fuel station: Costco North Miami Beach


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I figured there might not be a difference in mpgs in 87 -vs- 93 Octane at steady hwy speeds at sea level. You are probably using under 100 hp to maintain 60 mph. You might see different results in higher altitudes, hilly/mountainous terrain, higher interstate speeds of +80 mph, or hauling a heavier load when the MDX needs that extra performance from 91-93 octane.
 
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