Highway Fuel Economy worse than City?

[Centaurus5.0]

2011 v6 Mustang 48.5mpg. Average speed was roughly 44 mph.

http://www.motortrend.com/news/hypermiler-2011-ford-mustang-v6-averages-485-mpg-at-bristol-8104/

 

[DWZ]

This seems fairly obvious to me - why is there this much discussion? Unless something has changed, the EPA does it mileage tests at 55mph. So in order to show their best gas mileage, the car companies are going to tune their engines for peak effeciency at highways speeds of 55mph. The fast you go, the higher the revs, the higher the fuel consumption.

 

[metroplex]

I thought the EPA revised their highway testing about 10 years ago

 

[Odrapnew]

EPA Highway testing is more than just driving at a constant speed. I'm sure someone can dig up the test cycle, but there's acceleration, breaking, cruising...etc included in the Highway test.

55mph is not the ideal speed for mileage. Like shown above with the Mustang, if you're cruising at about 40-45mpg in the Explorer in 6th gear, constant speed, your mileage should be much better than EPA....but that's not really "highway" speeds.

In my 14 Sport, 70mph is right around 2000rpm. Your comparison of your XLT to the SHO is not really relevant. Different engines, different vehicles.
In the summer, constant speed of about 75mph, I typically get around 21-22MPG. I'm sure going 80-85mph will drop that down quite a bit.

 

[metroplex]

Both have the same 6F55 gear ratios except for final drive and tire size. The XLT final drive is 3.65 and is just a screamer on the freeway. The 3.5 are the same family except SHO has the same engine as the XSport with the twin turbos 2500 RPM in the XLT vs 2000 RPM in the SHO, big difference. I lose mpgs on average on the freeway versus cruising in the surface streets. I also suspect EPA test cycles are done on rollers with estimates for aero drag. The EPA highway cycle maxes at 60 mph as well briefly, which is unrealistic in Michigan and many states. 60 mph is what you can see on our large surface streets and 70 to 85 is what you reallistically see on the freeway.

But in all honesty my Fusion Sport and SHO get only about 1 to 2 mpg better gas mileage as my Explorer XLT, if that. I think my XLT average so far is 15.5 while SHO is 17.13 lifetime over 4 years of driving.

If they go to 10R80 with the 3.3 on the 2020 Explorer, the gas mileage should be much better on the Explorer since OD ratios are drastically different. Not much of a difference on the F150 or Mustang since 6R80 already has better gearing in OD.

 

[jo7hs2]

Just to chime in about the original post... With my 2018 XLT AWD, I’ve been getting consistent 22MPG highway. If I never set tires off the highway, I can maybe push that up to 23-24MPG. That’s at usual cruising speeds, not 55. Mixed rural driving works out to more like 19-20MPG. Haven’t done any city driving yet, as I don’t do much.

However... fuel economy was HORRIBLE the first two tanks of gas. Calculated, not just on the screen. The cyclone needed a little time to loosen up, clearly. Never had a vehicle get such horrible fuel economy during break in. It resolved about 250 miles in.

Also... I have noticed that, unlike my previous Ford vehicles, running the defrost (which engages the AC compressor) results in a significant drop in fuel economy. 1-2MPG on the highway. Usually, the difference was not noticeable on the highway beyond a very slight reduction in power, whereas it was noticeable in city traffic. I’m wondering if they used a very large compressor due to the extra passenger vents.

Additionally, as others have noted about temperature, and just like our Ecoboost Escape, we’ve noticed a significant drop in fuel economy when it is very cold, say below 20F. Interestingly, all my previous naturally aspirated Ford’s did not display this behavior, but the newer boosted Escape does. Clearly not a Ecoboost related matter, as our Explorer is naturally aspirated.

 

[peterk9]

If you drive 55-70 mph on a Michigan freeway, it's like stopping in the middle of a busy road. There's no way to really drive below 70-75 mph on the highways here in Michigan. Like I said, at 80 mph, the engine is screaming at 2500 RPM. I'd have to drop it down to 60 mph to stay around 2000 RPM. If I lived in Maryland or New Jersey where the highways are 55-60 mph, then yes I could see much better MPG numbers.

Had a chance to check mine yesterday as I don't get out on the highway that often. At 72 MPH the tach was almost but not quite up to 2000 RPM.

Peter

 

[Odrapnew]

Both have the same 6F55 gear ratios except for final drive and tire size. The XLT final drive is 3.65 and is just a screamer on the freeway. The 3.5 are the same family except SHO has the same engine as the XSport with the twin turbos 2500 RPM in the XLT vs 2000 RPM in the SHO, big difference. I lose mpgs on average on the freeway versus cruising in the surface streets. I also suspect EPA test cycles are done on rollers with estimates for aero drag. The EPA highway cycle maxes at 60 mph as well briefly, which is unrealistic in Michigan and many states. 60 mph is what you can see on our large surface streets and 70 to 85 is what you reallistically see on the freeway.

But in all honesty my Fusion Sport and SHO get only about 1 to 2 mpg better gas mileage as my Explorer XLT, if that. I think my XLT average so far is 15.5 while SHO is 17.13 lifetime over 4 years of driving.

If they go to 10R80 with the 3.3 on the 2020 Explorer, the gas mileage should be much better on the Explorer since OD ratios are drastically different. Not much of a difference on the F150 or Mustang since 6R80 already has better gearing in OD.

It just might be that your average freeway speeds are much higher than the EPA testing, therefore you don't see the typical highway MPG bump.
Remember, drag force increases with the square of your speed. There's about 30% more drag force @ 80mph vs. 70mph.

I don't think you can compare the naturally aspirated 3.5 V6 to the Twin Turbo Ecoboost 3.5 V6 for highway rpm The Ecoboost makes good torque at low rpm, so it doesn't need to run at the higher RPM to be more in the powerband . I'm sure the n/a V6 has a higher highway rpm to get it closer to peak torque. Peter confirmed that the Ecoboost runs about where mine runs @ highway speeds, which is more in line with the SHO.

 

[jo7hs2]

My 2018 XLT (3.5NA, 4WD, 6F55) does ~1600RPM @ 55MPH ~2000 @ 65, ~2100 @ 70, and ~2200-2300 @ 75.

 

[Odrapnew]

As soon as the weather gets above about 40F ambient, my gas mileage is noticeably better. Below 40F, even around 30F, it is just as bad as it is when it is -10F to 30F.

I wanted to comment on this as well. I notice the same thing. Same gas(same tank), same driving cycle. Once temp gets near and above 40F, mileage "skyrockets." By that I mean it's about 2mpg better. Doesn't sound like much, but that's more than 10% increase.

Sure, oil and fluids take longer to heat up when it's cold, but once up to operating temperature, the mileage should be similar.

I guess I've never noticed that in other vehicles I've owned, but I didn't track them as closely as my Sport.