2018 5.0 Highway MPG

[millhouse]

That's an assumption on your part. In my ~8000 miles since buying my 2016 GT last November, I've seen computer numbers as high as 25 to 26 mpg. Most of my local driving averages upper 21's to low 22's. All of my manual calculations have averaged around 1.5 mpg less, give or take, than what the computer says. So your assertion that the error will increase with speed and larger mpg values does not prove true by my experience.

Like Houston Kid said,

He's taking a margin of error for a much longer duration at much different operating conditions and applying it to a much shorter duration with completely different conditions. It's not an assumption, it's bad science.

You are correct and by that reasoning the error factor would be less fir the 32 mpg test because that was based on a speed of 60 mph. The 17.3 mpg average was based on city driving approx 80 miles slow speed cpu avg of 11 and highway driving the remaining milage at speeds up to 130 mph with an avg around 75 thus increasing the error according to your logic.

https://www.sciencebuddies.org/science-fair-projects/science-fair/steps-of-the-scientific-method

"Test Your Hypothesis by Doing an Experiment: Your experiment tests whether your prediction is accurate and thus your hypothesis is supported or not. It is important for your experiment to be a fair test. You conduct a fair test by making sure that you change only one factor at a time while keeping all other conditions the same."

All you have determined is that for the driving conditions that yielded a 17.3mpg average that you have a measured vs calculated delta of 1.5mpg. Again, applying that to a steady state test at 60mph is bad science. Also, naturally speaking, as your speed increases...so will the deviation of your mph and mpg. You are also relying on the MPG to be accurate for all of the acceleration and deceleration which should not be included for your steady state tests.

If you want to do a much more accurate test, fill up....gently accelerate on the freeway, run your 20+ miles, gently decelerate at the exit with a gas station near and fill it back up. It's possible you'll still be off by 1.5 mpg, but don't assume that your previous test is accurate for steady state conditions.

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[Houston Kid]

Prove it otherwise not to be accurate.

If you don’t like the test do your own and disprove the results. Easy enough.

Have you ever driven and tracked the milage in a 18 with the A10 and 3.15 rear end?

 

[millhouse]

Prove it otherwise not to be accurate.

If you don’t like the test do your own and disprove the results. Easy enough.

Have you ever driven and tracked the milage in a 18 with the A10 and 3.15 rear end?

I don't need to prove anything...but you cannot run a transient condition, full tank test and reasonably expect the numbers to be the same as a short term, partial tank steady state test. I mean...again, you can...but you'd be wrong in doing so. If you still don't understand why, I don't know what to tell you. :shrug:

 

[Houston Kid]

Nor do I because the numbers speak for themselves.

The numbers can be taken anyway you want to based on interpretation. Like most unscientific tests.

I have never claimed the numbers were anything other than what they are.

 

[millhouse]

Nor do I because the numbers speak for themselves.

The numbers can be taken anyway you want to based on interpertation.

I have never claimed the numbers were anything other than what they are.

Again, you aren't understanding. I'm not doubting your ~ 1mpg difference...you just can't apply that long term transient test to a short term steady state test.

All you've shown is that in mixed driving with a shitload of variables that your final measured results were within 1mpg of the calculated results. It has nothing to do with what would happen in a short term, steady state test.

I could do 100 WOT 1/4 mile passes and find my calculated vs measured delta. You cannot reasonably expect the results however to apply to cruising on the highway at steady state. It's an extreme example, but in essence....what you're trying to do.

 

[Houston Kid]

I completely understand what you are saying and do not dispute the unlimited factors but considering we, well at least not I, am not a scientist. I am completely satisfied with the 22 mile numbers adjusting with a error 1.5 mpg.

So at this point we are going to agree to disagree.

 

[757DRVR]

Just checked milage figured the old fashioned way.

578.8 miles driven using 22.2 gallons. 26.07 MPG. My computer registers 27.0.

 

[GT-SV]

Just checked milage figured the old fashioned way.

578.8 miles driven using 22.2 gallons. 26.07 MPG. My computer registers 27.0.

Nice long trip. What were the typical crusing speeds (mph)?

 

[MaxHedrm]

I'm at 20.6 avg mpg calculated as of my last fill up at 875 miles. My best fill up was 21.8 on a road trip.

As a side note, it seems the car's calculation on every car I've tracked it (a couple Fords, a VW, & an Audi) is consistently optimistic by around 1 mpg. You'd think they could get this right, so they must not want to.

 

[Deleted member 33561]

Your MPG is hard to quantify except to drive your car on a trip and then calculate the actual mpg. That does not mean you will get the same mpg next time on the exact same trip. Take an example of a "low" pressure area over your trip. Say you are on the east side of the low pressure area going North. The "low" can give you tail winds of 20 mph with gust to 35 or more which will give you great mpg. lets say you turn around and make the trip back to where you came about 10 hours later and the "low" has moved on further to the east. You can now have the same tail wind conditions because you are now on the West side of the "low". ("Lows" have a circular wind counter-clockwise). This will give you great mileage for the whole trip that you may never repeat again. Of course the exact opposite effect is also possible (headwind in both directions).
(If you're getting 30 mpg in your V8 Mustang, you're not driving it right.)

 

[757DRVR]

Nice long trip. What were the typical crusing speeds (mph)?

It's actually a week and a half to & from work. About 90 miles round trip. Highway, but stop and go for 25% of the time. When you can go full speed the flow is 75-80 MPH.
The route is 90% interstate and 10% city.

Denver traffic is horrible during what should be called "crawl hour" instead of "rush hour".

;)

 

[hinch]

It's actually a week and a half to & from work. About 90 miles round trip. Highway, but stop and go for 25% of the time. When you can go full speed the flow is 75-80 MPH.
The route is 90% interstate and 10% city.

Denver traffic is horrible during what should be called "crawl hour" instead of "rush hour".

;)

Don't say that you'll put me off moving to the area at some point this year

 

[LOEzell]

I just completed a 106 mile drive on the Natchez Trace Parkway from Clinton, MS to just outside Eupora, MS. Driving a constant 57-mph (speed limit is 50 but the Rangers give a little slack), I averaged 31.7 mpg according to the vehicle computer. I realize the trip computer seems to error on the high side and my speed supports fuel mileage. However, I am pleased with 31.7 mpg in a 460-Hp, 5.0 L V8, 10 sp, top down.

 

[wireeater]

With my spirited driving. I have an average of 18.9 for 3400 miles.

 

[88lx50]

Trip computer is telling me I got 26.4 mpg on a 180 mile highway trip to the Ford Nationals in my GT manual convertible. Not sure how accurate it is, but considering fuel usage, it sounds close. Most of the trip was 85 mph.

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