Mileage in-town vs. highway

I think it's hard to generalize and the EPA's ratings prove that. They may be useful for making comparisons between competing car models, but beyond that, as they say YMMV. I have noticed that both our Gen 2 and Gen 4 cars get their best MPG under what may best be described as heavy traffic conditions, where there is a lot of slowing down and speeding up, but not too much time actually standing still. That would probably not be considered either true highway or true in-town driving. While it is a fact that the ICE shuts off a few moments after the car comes to a stop to save gas, I don't think the car can achieve its best fuel efficiency if it is just going from one stop light to the next and then sitting for a few minutes. If that is what you are considering in-town driving, I don't think you would ever be able to match highway driving MPG, unless of course your highway driving consists of going 80+ MPH.

 

definitely the epa protocol. if you could duplicate it, you would get their results. the biggest problem from my point of view is, 'city' could mean a lot of different things, and highway speed. try driving 80.

 

I noticed if you have decent stretches of road in the city where you can hold a constant speed, it gets really good mileage. If it's a lot of short stop and go, it sucks.

SM-N950U ?

 

I think the EPA cycle was more of an suburb than urban stop and go. When I had my 2005 it always got great mpg in the suburbs of Nashville, getting 50+ mpg with over 200k miles. The highway was a different story, it got in the mid to low 40's. And that was with setting cruise to 70 mph. Never knew why it didn't get better on the highway, I was always trying things, like spark plugs, fuel additives, tire pressure, but at the end of the day, that car is still in the family with 320k and running everyday! So it doesn't matter too much but I thought I would share.

 

There is a road in my town that I use to go to my studio. It's 35 mph and flat. When the temperature is decent, my gas engine shuts off on that road, and I usually end up with a 75 or 80 mpg estimate on the consumption screen for the 5 minute block that contains that stretch.

SM-N950U ?

 

Must depend on what you consider in town vs highway, I drive 15 miles on 35mph roads to get anywhere so my in town milage, well with the gen2 was 50-60mpg while my highway mileage was well below that, vs the OP whose in town driving is in Minneapolis, stop and go I imagine.

 

I live in a small town, but work in a large town. Luckily, I'm on the far reaches of the city limits where money of the stop and go thins out.
Highway mileage, I get better mileage traveling east. Besides a trail wind, I also am going lower in elevation ever so slightly. According to google, it's a total of 76ft, lol, but I can see that it makes a difference in a 50 mile drive, per the display in the prius

SM-N950U ?

 

My experience has pretty much been the same but I can see where the numbers are coming from. On the open highway running between 65 and 80 mph I average 43-45 mpg. The roads locally are mostly 45 mph but with lights and stop signs. That usually nets between 39 and 42 mpg. On the freeway in fairly heavy traffic, though, the car really shines. Running 35-55 mph or stop-and-go without actually coming to full stops most of the time the car delivers 48-50 mpg. I suspect the EPA city testing averaged out reasonably close to those conditions.

 

Hard acceleration hurts mileage pretty badly. Late braking is even worse. I get about 50 mpg on the interstate at 70 mph and about 70 mpg in the city where limits are in the 35-45 range with occasional stops. On the suburban roads where the speed limit is 60 mph and I have to stop once or twice per mile, I get well under 50 mpg. All that would be without plugging in. A Gen 2 will not be as good, but the ratios should be similar.

 

Tom,

You live in MN, it is cold there (here actually) and lots of AC use in the summer. Cold engines and lots of AC burns more fuel because the Prius will run the engine hard to supply cabin heat even while stationary; something nearly no other vehicle does.

Also, MN does not have the high freeway speeds of TX for example, so 10 MPH slower = less average fuel used per mile.

 

i think you have answered your own question. we don't know the test, and ymmv

 

It is an artifact of an EPA labeling system that was designed for a different generation and type (traditional non-hybrid) car, and includes empirical fudge factors. Under the calculations used from about 1985 until at least 2015 (I haven't kept track of 2016+ changes), the City number was discounted only 10% from its corresponding CAFE test cycle, while the Highway number was discounted 28%.

The tests use driving cycles that match almost no-one's actual driving. And people driver faster and accelerate harder now than with the smaller engines back then.

The cycles are described in Section 1 here:

CleanMPG.com: Beating the EPA - The Why’s and How to Hypermile
Section I - History and methods of the EPA’s Fuel Economy estimates

 

The tests are done with pure (ethanol-free) gas too, fwiw.

 

They don't even measure fuel volume at all, but instead measure just the tailpipe emissions, and compute backwards from there. This allows them to use any reasonably appropriate fuel, and the EPA has expanded the formulas to allow computational adjustment back to some reference fuel formulation.

Considering how many times the labeling scale has been adjusted downwards, I'm not so sure the pure gas vs E10 issue is all that relevant anymore. Yes, it is a 3% difference, but the other adjustments and fudge factors and scale downgrades are larger.

 

It's the automobile manufacturers doing the testing still, is it not? Following the criteria (hopefully), but still, a classic case of the fox guarding the hen house.

 

All the tests assume the Prius engine is warmed up. It can take 2 - 3 miles for that to happen. Fuel economy on short trips in a Prius is horrible. If your city driving is when you first start your trip, the mpg will be much worse than highway with a warmed up engine.

 

Yes, and several manufacturers have been caught raiding the hen house / lying on their test results. They've had to retroactively reduce the numbers, and compensate the customers.

For Euro rating tests, they don't even have to lie. The looser test rules and tolerances leave more room for the makers to push up against limits and bias tests, and they have pushed it to an art form.