I have noticed on the press releases of the new 911 Black and previously for the 911 GTS that the published figures are 19 city and 27 highway.

Our owners manual simply said TBD so I never considered this before. Not seriously. But this makes me wonder. We consistently get 17.3 in a mix of city and freeway *** rural highways. On other cars, including exotics, I've seen results somewhere above halfway between the manufacturer's city and highway numbers, so I doubt it is my driving style causing low mileage results. But this is our first Porsche.

What are others seeing? Does the S regularly deliver less than the advertised 19 mpg? Or is it possible to have a tuning issue causing high consumption. Offhand, I can't see what it would be with a DFI engine running under near total computer control, but we're in the last year of our warranty so if something is going on, I'd like to find out now.

Any thoughts?

Gary

 

I get 27mpg on the highway - sometimes 28. 27 is easy - 28 takes really consistent speed. I have only tested this at the higher end of typical highway speeds. Can't say if 55mph or anything in that area would do better or worse.

In the city, I have not really paid much attention in a good while. Seems like I could get anywhere from 12-20 depending on how I drove it - with manual shifts, I was not nearly as efficient as the computer on auto.

 

I'm getting pretty good mileage, although I haven't done a detailed check. Having said that, I didn't buy the car to save gas, I bought the car because it's a Porsche, a sports car. If I'd wanted a fuel mizer, I would have bought a Prius, or a VW deisel Jetta... or maybe not..

I'm a pretty simple guy, when it needs gas, I fill it up.

 

Don't believe the ratings, they are done inside a vacuum with no wind, hills, or other real world influences (like turns). They are just a benchmark for comparing one car to another.

 

my commute is a mix of 45mph roads and 65 highways. Not much stop and go. I average 21.5-21.8 depending on the season.
For full highway drives, I can get 25-26.
Autocross and event weekends gets me 12 mpg

 

I average ~15 mpg in daily driving. My C63 got roughly the same.

I had a MINI Cooper S and never saw above 21 mpg, so my driving may be suspect.

 

Although I have an 05 C2S I may have something to add. I track my mileage religiously using www.mymilemarker.com. Although there are loads of factors for calculating why your mileage may be lower than others, mine is defined by the amount and type of travel I do. 90% of my driving (so almost every time I drive) is city and under 5 miles. The most wasteful time in gas usage is while your engine is cold, and since I don’t get out of that state more than once a week I waste tons of gas. The ECU gives a richer formula when the engine is cold to prevent knocking. Over a nine month period and 3,682 miles I have averaged 14.2 mpg.

 

Yeah, and back in 2004 when the '05 997S came out the EPA ratings were 20/25. I get about 15-18 mpg on average - live in the city so a lot of stop and go. When I do roadtrips with all highway, I can get 27 mpg!

I also wondered if there was something wrong with my car during the intial months of ownership. I'm coming out of an '04 S2000 also EPA rated 20/25 but I'd drive the hell out of that thing and couldn't get much worse than 20 mpg!

Anyways, sounds like my car/driving is inline with everyone else...

 

Combined 20/22 depending on mix, usually more towards highway. Highway 26-27.

 

My 04 WRX I drove much the same way and was always in the mid/low 20s. My 07 STi was 1 mpg better than my C2S. Your 04 S2000 was 2L as well was my 04 WRX. The STi was 2.5 and made way more power with a larger turbo and fuel injectors. These cars make lots of power and are 3.6/3.8 so it really only makes sense since they were not designed to be hyper milers.

 

I find mileage comparisons very difficult to make sense of. I find that it is so dependent on conditions, speed, and driving style, it is impossible to make meaningful comparisons. I've never got more than 25 mpg on freeway trips, but if I drove closer to 65 instead of 75 or 80, I'd likely do much better. Similarly, in my daily 6-7 mile commute to work it can vary from 12 to 19 depending on route, speed, etc.

 

Jaunting around town - plus I never shift before 4k and always have the Sport button On - I get about 12 mpg! Sure, in 6th on the highway loafing along, the car will show 25 mpg +. Normal, spirited driving, the mileage is horrible.

 

Well, we always talked that way, we hotshoes I mean, but it was never completely true. The 'city' value requires starting with a cold engine and making 23 stops over a period of 31 minutes for an average speed of 20 mph (32 km/h) and with a top speed of 56 mph (90 km/h). For the 'highway' value, the engine is warmed up and no stops are required. They must average 48 mph including a top speed of 60 mph while covering a ten mile distance. After that, they adjust the city value down by an arbitrary 10% to make it more realistic, and the highway value by 22%.

That certainly isn't my pattern of driving, but neither is it coddling the car. Nearly one fifth of the city cycle is mandatorily spent idling. Nevertheless, people who really care about their fuel economy didn't use the value just to compare possible purchases. They wanted to see those results by God and be damned to the liars that gave them a car that wouldn't do those numbers with their own personal style of driving. So the EPA changed things as of the 2008 models.


They added three new tests that go into the overall mileage rating.

1. High speed, quick acceleration cycle. An eight mile loop that lasts ten minutes and includes 80 mph as top speed and four stops, followed by acceleration that is not Porsche class, but certainly brisk for most cars. They must manage an acceleration that is about like a 0-60 run of seven seconds. (8.46 mph per second, for all love. Wonder how they arrived at that value?) The overall average is still 48 mph as in the 'highway' number, but with those four stops in eight miles, that's a pretty stout average. The ambient must (or can? or does? I'm not sure...) range from 68°F (20°C) to 86°F (30°C). Not what we call hot in this neighborhood, but not optimized for fuel economy either. The engine starts warm and the air conditioning is off.
2. Air Conditioning Cycle. They bump the required ambient temp to 95°F (35°C) and go through a cycle that is about like the city cycle on steroids. More acceleration, higher average speed, and what have you.
3. Cold Weather Cycle. Drop the ambient to 20°F (-7°C) and repeat the standard 'city' cycle.

None of that will push the results into the category of an enthusiast driver when we're driving enthusiastically, but honestly I spend most of my time driving more conservatively than the Honda Civics and SUV's around me. If I didn't, I would halve my time for each run, but average one ticket a week. As I said, my usual results with performance cars in my typical driving cycle have been mileages a little above the point halfway between 'city' and 'highway' numbers in the past. In other words, I should be doing a little better than the new EPA value that combines those original tests with the three new ones.

Until the 2012 models come out, manufacturers can use data from the old test cycles, but it goes into an elaborate set of equations that predict the result of the new tests. With their high-technology culture and their consulting role to other manufacturers, I imagine Porsche already has the capability in house to do the new tests, so their cars should be showing results based on the actual new tests. The waiver helps companies that need the six years look ahead to make the capital outlay the tests require.

I think we can consider the "overall average" value to be reasonable even for sports cars as long as we're talking about our normal driving. That is, our "God I wish I'd had time for a cuppa coffee but I gotta get to work" style of driving.

Now on track days...

Gary

 

Well, sure. As you say, I'd be driving something else if the absolute mileage mattered to me. What concerns me is the car may have a problem that is showing in the fuel mileage.

Gary

 

This may be closest to my driving pattern, Alan. When I say 'city' here, I'm really talking about averaging forty to fifty mph while not stopped at lights, and the lights are pretty well spaced. I fooled around a little bit today, resetting the mileage figure every time I changed conditions. I never saw better than 23 mpg on the freeway at 70 mph and couldn't get a decent figure for town because a traffic accident changed conditions, but it looked like 12 was where it wanted to settle.

If I confirm that in more usual conditions tomorrow, I'll start looking for a condition to blame because our 2009 S models are reported as 18/25 with a combined value with the new tests of 21 mpg. Even allowing for enthusiasm, I expect to see a value within ten percent of that newly computed 'combined' value, and I more like twenty percent lower.

Gary