gas mileage... seriously?

city driving: 11-12mpg mixed with highway: 18-20 both above are via the trip computer average am i crazy to think that porsche said its 18-26?? I dont drive the car hard (when <180 i shift at 2900-3k, when operating temp usually at 37-4000, occasionally once a day hitting 5-6k) When i'm cruising down city streets RPM is at 22-2300 ish (level ground, not lugging). When i go out for the night, drive about 20-30 miles, my tank goes down at least 1/8 maybe even 1/4. could something be wrong? am i burning too much fuel or is this normal??

Bear in mind that I have no cats, BB exhaust and an intake. I get 20mpg. Would say this is 50:50 Highway:City.

I get about 20 mpg easy in my 996 and that is not driving like a grandma. Have you checked your air filter? My Dodge Durango 5.9 R/T gets the same mpg you are getting. EDIT: I do have a Fabspeed intake and new plugs.

I pay no attention to it

Somebody keep pressing on my accelerator too much. I don't think the 2+ mile hill helps either.

I have the same problem--though my numbers aren't as bad as yours. I'm around 15 in town and 24 on the highway (which seems to be getting worse). I don't drive hard as I frequently have my daughter in the back seat. New plugs, air filter, etc. I'm wondering if there isn't a lifter that is stuck or not working properly. Can a dirty MAF cause this? I haven't cleaned this since I bought the car a year and a half ago.

don't worry too much about it, but, I use mine as a DD, and typically average 23-24mpg driving it like a "normal"car in mixed city/hwy driving...have gotten up to 28mpg cruising on the hwy....when having fun, and driving it aggressively that drops to the teens....

Sounds very low for me unless you are on the track ... I get 18 in the city and have seen 26-28 on the freeway at mostly constant 70mph 50 mile run. Mixed is normally 19-22 ish. 3.6l 6spd Have you changed your plugs & airfilter recently ? Mileage could be much worse in very cold weather (esp. short trips). If there is no CEL (for MAF or o2 sensor for example) I'm not sure what I'd check next - but i'm sure there are plenty of other ideas from the board here ....

Sounds like something isn't right. I have a Carrera 4 with Tiptronic and get 18-19 in the city. Have seen 28 on the highway in August with the air conditioner on.

I average about 18 mixed city/highway, which I think is pretty darned good for a car with 420hp. I get 28 on a level highway at 70. Honestly, I don't really care what my mileage is, but it was a pleasant surprise that it does as well as it does.

I drive the crap out of my car. Mostly city driving. I average about 20 most of the time. On the highway I get average about 25-26.

I'm usually around 15mpg mostly city driving. I'm planning to change plugs and maybe coils this summer (just rolled 82k miles on original plugs).

I average 18-20 in city/back roads not much hwy driving. I have been able to top 20 at times.

Using 6 gears helps. This is what I normally see, with mixed city driving. Take city driving and times is by 2 and that's what my car sees on the track!

I have a combine 19mpg since I've owned the car in 2004... oh and it's a Porsche 911, so no crying at the pump. Fast, Reliable, Cheap. Pick any two.

2003 6 spd. last 4 tankfuls all city-low speed back roads 21mpg on the computer, hwy 27-29 using cruise @~75

I think I get around 20 mixed driving. How often do you guys clean the throttle body? I cleaned mine when I got the car 5 years ago - does gunk build up more frequently?

19/20 in mixed driving, 25-27 on the highway if I keep it under 80... So not much. It may be heresy, but I wish 6th was geared a little higher. 3000 rpm in top gear at 80 is not really necessary. I read that the 7th in the 991 is a true economy gear.

I have a combined 21 since I bought it. I have done 26 and 27 mpg on long stretches of highway doing between 65 and 70 mph. I averaged 25 on a trip from Atlanta to Illinois.

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So far, I've lucked out and my car has been all three for me! (I suppose the "cheap" part is relative...) I average around 19mpg for daily driving, 24mpg when I spend a lot of time on the freeway. This is calculating using the miles driven/gallons to fill up method, but the dash is pretty close usually.

Yes, cheap is definitely relative.

Almost all of my driving is local (no highway) and I average 17-18mpg. When I do get out on the highway the mileage greatly improves. TO the OP, unless you are launching from every light (doesn't sound like you are) something isn't quite right. I think it's Durametric time for you.

According to the PCM "mileage since HH:MM" setting I'm getting 17-19 on my daily commute, but if I switch to the "Onboard Computer" or "Continuous" reading, it's 16.4. The only sure way is to top off the tank, drive it until it's under 1/4 or the warning light goes on, then top it off again and do the maths. I've always found that to be more accurate (and usually lower, unfortunately) than the onboard gizmo in any car. What really kills the mileage is idling. Mine seems to drink at stoplights like a dog who just chased down a rabbit.

i'm def going to take it to my P-mechanic to clean out the air filter, MAP, and see what he says about this terrible mileage

2002 C2 6-speed. My daily driver, average 50-60 miles per day 1/2 hwy & 1/2 city. I average 23.5 to 24mpg fill up after fill up. And the answer to your next question: YES! I do drive like an old grandma. But I do step on it once in a while!

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It sounds like your mileage is pretty typical if you are getting 18-20 in mixed city/highway driving. It's not an economy car.

My trip computer shows a city average of 18 MPG. I averaged about 6-7 MPG on the track this past weekend!

26 on the highway, 19 around town, 8 around the track.

I would not trust the trip computer. Fill the tank and check your mileage the old fashioned way to make sure.

Without cussing.........I think a lot of the good mileage numbers are guys running NON ethanol gasoline. My whole ocean locked islands is forced by law to use the meth addicts ethanol. What I'd like to know is if there is anybody using the ethanol getting good gas mileage. The highest octane here is 92 and a local report said the 92 here is lower than 92. I believe this since my mileage is lousy. There is also the factor of a hwy mile markers actual mile is .8 mile on my odometer. So I should actually add 20% to the miles before dividing it by the gallons pumped.

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You have the same results as me. I really do not worry about the MPG on it.

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All gas in Chicago contains ethanol. Over 90% of it outside of Chicago contains ethanol. All of my mileage numbers are based on ethanol blended gas.

nope....all gas in CT is 10% ethanol... BTW....this is one of the things I love about this car.....run it to redline all day at the track, and get econobox mileage on the way home.....

On the last 115 miles computer said 21 mpg. No highway back roads and city driving.

I daily drive 74 km per day, an almost 50:50 split of city and highway. I drive on the hard side of average - similar to the OP's description of his own style. consistently average for the car is 13.3 litres/100km = 17.7 mp(US)g

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All I can buy is 91 octane with ethanol in it and my 02 Boxster gets (just this last tank) 24.3mpg in mixed (though mostly highway) driving. My 03 Turbo gets around just on either side 20mpg in similar driving. Whether the mpg is 19.something or 20.something depends upon how mpg aware I drive. On the highway/open road like on a long road trip the Boxster's mpg will climb to 27 or 28mpg while the Turbo's mpg can climb -- if I'm very very good -- to around 25mpg or 26mpg. In both cases the car's speed average approaches the posted max. limit for the highway so the car's averaging 75mph or thereabouts. I do not have an instantaneous mpg readout in either car but in an 06 GTO (6.0l 400hp (larger engine but similar output as my 03 Turbo) which had this feature under hard acceleration the mpg number could drop to 5mpg. OTOH in 6th gear at around 1500 rpms the mpg could climb to 30+mpg. (In the Turbo if I really give the engine the whip the gas gage needle sinks as I watch it. That engine can inhale some gasoline.) If the CEL is not on and there are no other signs of any engine problems I'd say your driving is the cause for the lower gas mileage. It doesn't take much idling, in town driving with stop/go driving, or hard acceleration or even climbing grades to see the fuel consumption go up. And once up then one has to drive even more conservatively to compensate and that's often hard to do. Sincerely, Macster.

yea no CEL light, no engine problems that i'm aware of. thanks for the replies... now reply to my radio needs please! haha

very hard to find non-ethanol fuel anywhere! I think there is a total of 3 stations in the whole state of washington that sell it, it was a little easier when I lived in Georgia, I noticed about a 15% difference in mileage with non-ethanol fuel

Clean maf Fuel injection cleaner O2 sensors Air cleaner

Yah thanks guys. I've been slacking only using chevron gas to figure I was cleaning the injectors. Of course it is a new engine.....hmmmmm. Yah rings need breaking in I guess. The MAF is going to get sprayed down soon I guess. Where's the O2 sensors?

My rule of thumb: if you're not in the teens, you're not driving it hard enough like it should be.

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+1... i get about 18.4 50/50 high way and rather annoying city driving.

I do quite a bit of city driving, and usually stay in the 2-4k RPM range, and average around 17.5-18 MPG. On the highway, I'm around 25ish. She's a '99 with 80k miles on her. Obviously, only premium, and we have the 10% ethanol mix here as well.

In all honesty, city driving is so varied with so many different variables. So just because you are getting low mileage doesn't necessarily mean you need to panic. A more consistent data point would be for example traveling on the highway with your cruise control set to 70 for a decent stretch and see where you net out. If you're nowhere near the mid 20's at least, something is definitely wrong.(not to account for hills/mountain areas)

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Chevron gasoline is a good gasoline. There are other brands equally as good. Given regular usage of a quality brand of gasoline the fuel system -- from tank to injectors -- and the intake/engine combustion chambers from the valves thorough the chambers and the O2 sensors and even the converters -- should be free of any gruesome deposits. If a sub-par grade of gasoline was used for a while before you switched to Chevon, there can be build up that just Chevron gasoline (with 'Techron') alone can't remove. If this is suspected to be the case, a bottle or two of Techron can be used to remove this build up. Then from this point on regular use of Chevron (or a comparable gasoline) can keep the deposit build up down. Use Techron according to instructions and I like to arrange the use of this so after the last tank is down to say a quarter of a tank or less remaining fuel, change the oil/filter. Cleaning the MAF... sigh. I have driven tens of thousands of miles and have cleaned the MAF in my Boxster just 2 times. Once when I suspected it being dirty (or something) and being the cause of engine symptoms that proved to be a bad AOS. I cleaned the MAF over a white paper towel. There no signs of any dirt. And this was after nearly 80K miles of being in the intake. Stock air intake system with properly spaced out air filter changes. The other time when I suspected again the MAF might be 'dirty' but this time the cause of the problem (after I replaced the MAF) to be a leaking oil filler tube cap). But again at this cleaning the MAF was not dirty. As for the O2 sensors, leave them alone unless error codes point to one or more bad ones then replace the bad ones and drive on. Oh, I have put on nearly 80K miles on my Turbo and I can't even tell you where the MAF is, let alone have I bothered to clean it. Be careful you don't overreact to what appears to be gasoline consumption that is well within an acceptable range, though a bit higher than you might like. Gas consumption is like oil consumption. Engines vary a bit in how much gas they consume, how much oil they consume. Also, drivers contribute to this variability too. Someone always gets better fuel consumption under the 'same driving conditions' and someone will always report less oil consumed 'under the same driving conditions'. They are of course I'm sure passing on accurate info. But this doesn't mean your car's junk or even needs work because its numbers are a bit different. Sincerely, Macster.

SOOOO many factors go into observed gas mileage. I drive from Jacksonville, Florida to Cleveland, Ohio round trip at least once a year. It is 930 miles each way. Jacksonville is a coastal city and thus is essentially at Sea Level and very moderate temps year 'round. I average 23.8 in mixed daily driving here, 93 octane, quality gas. Measurements on Florida flat highway road trips can see 27-28 mpg average, with short distances over 30 mpg (highest ever 5 mile stretch measurement is 33.1 mpg on a section between Jax to Daytona, and repeatable, both north and south, every time I drive it, which is about a dozen times a year). Cleveland is at 800 feet above sea level. In between the two cities is the Appalachian Mountains with the highest highway passes approaching 4000 feet above sea level on I-77. The trip up is fairly flat until I get to Columbia, SC. I usually refuel just north of Statesville, NC either direction. I always think I should get the best mileage for my trip on the flat, low altitude southern leg. That is NEVER the case, whether I am driving the 996, the 2007 Civic, or the '05 Jeep Grand Cherokee with HEMI. I ALWAYS get better highway mileage on the NORTHERN half of the trip which is all mountains and hills - often by 10% better mpg . I always drive on cruise control and I don't hot foot on the interstates. Different gas in those northern states (all of the gas I buy has 10% ethanol)? Long downhill grades exceed the long uphill grades in the computers calculations (same grades on both directions)? Regional variation in gas mixtures work better in my car up north? And what is so unique about that one section of I-95 between Jax and Daytona (for one thing there are no highway overpasses on that section)?

I usually fill up with Chevron or Shell. We have 93 octane, 10% ethanol in Houston. Today I filled up at a Valero station. I don't know about the mileage, but dang if the car didn't feel peppier. I don't know if it was the gas or just the fact that it was a glorious day and I had a light schedule and took the afternoon off for the first time in 3 months. Regardless, I have noticed that certain additive packages in different brands seem to make a difference. My 335 definitely did better on Cheveron. I'll try the Valero again to see of my initial impressing holds.

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Yep, absolutely identical to what I get. No complaints at all, really. I don't think the ethanol is an issue, but whether or not it is oxygenated, does. When I get gas well outside of populated areas, mileage and pep is always improved.

15mpg peppy city, not many lights, not sure on hwy, for some odd reason I get I-29 confused with the Autobahn. 3.4 tip btw.

If somebody knows how to leave a light slowly like a regular car can you please tell me?

I just completed a looooong roadtrip from NYC to Chicago and back. Got ~27mpg. All the way on I-80, cruising at ~75-80mph (plus occasional bursts :P) and small drives around Chicago I used 93 octane fuel (~64 gals. and ~1650 miles). I'd say not bad at all for a performance car

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Pretend your naggy mom/wife/girlfriend/grandma/daughter is in the passenger seat and you don't want to listen to her complain about your driving.

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Get a quote on a new clutch and a new set of tires. Sincerely, Macster.

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. I do it all the time in my Accord, but I take you meant in the Porsche... Never occurred to me to try. I guess that wasn't very helpful. Oh and 21.8 in 10% ethanol infused mixed driving. I've checked the computer 2 or 3 times it's always been very accurate.

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I'm very curious what you think. A Valero just opened and it nearly abuts my driveway. I put it in my Accord and Ranger. I've been reluctant to use it in Babette, the Targa.

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Pac if I want to I am able to leave the clutch out slowly and when I feel it engage I hold the RPMs at 900. The car moves smoothly and slowly off the line. I also have a new clutch which helps.

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Valero is not a top tier gas. Here's a link to a list of top tier gasolines: http://www.toptiergas.com/retailers.html I read -- where I have forgotten -- that Varlero's refineries are designed to refine a lower grade of crude oil which of course costs less money to buy, and gives Valero greater flexibility in what crude oil it can use, but lower grade of crude oil costs more to refine and yields less gasoline per barrel of crude. Now I realize that this doesn't necessarily mean Valero gas is bad gasoline because it starts out with lower quality (less 'sweet') crude oil base stock. But unless it has changed, that it is not a top tier gas means I do not use Valero gas in any of my cars and I'm probably not gong to. Sincerely, Macster.

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Thanks for the link. I was surprised Sunoco was not on the list. Given a choice it's what I put in. Your correct about Valero's capabilities. In addition i have read they are the only U.S. refiner which can refine the lowest grades of oils Those capabilities also make them the largest refiner in the U.S.

2000 996 19 city 29 hwy top closed. N/A but not stock. Oh and I calculate my mileage based on the amount of gas I put in the car vs the trip mileage counter, which I set to zero at the gas station at each fill up.

Processing a Variety of Crude Stocks As an independent refiner, Valero does not drill for oil. It purchases a variety of feedstocks and is able to adjust its feedstock mix based on market conditions. http://www.valero.com/OurBusiness/Pa...rBusiness.aspx Making Products from Gasoline to Asphalt Valero’s refineries produce gasoline, diesel, jet fuel, asphalt, petrochemicals, lubricants and other refined products. Key to Valero’s success has been its ability to upgrade and expand refining operations to produce high-value, clean fuels from a wide variety of crude feedstocks – two-thirds of which come from discounted feedstocks. Valero acquires crude oil from producing leases, domestic oil trading centers and ships delivering cargoes of foreign and domestic oil. Heavy sour and residual oil; medium sour oil; and light sweet and other oil each represent about one-third of the feedstocks...

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+1 My wife has a 2010 Subaru Outback. When she drives it to my folks house (120mi secondary roads round trip) we avg ~19mpg. When I drive we avg ~24mpg. Same roads, same gas, same time of year. She has a heavier foot on gas and brakes.

Yesterday driving to San Jose (300 mile round trip), I managed 27mpg. And this included thrashing the car around the street, but mostly highway miles. Another thing I noticed after the rebuild is while cruising on the highway the temp gauge pretty much stays at the 180 line (or just slightly below). with engine coolant temp around 174.

That 6th gear is magical and really helps propel the car into the mid to upper 20's on the highway. I'm glad I have it.

You guys don't know much about the gasoline refining and distribution business do you? The primary difference between brands of gasoline is the additive packages the different retailers use. Gasoline is a commodity and is traded extensively to meet supply and demand. Chervron and Shell don't refine all the gas they sell. I know for a fact that Valero sells a lot of what they refine to other retailers including Chevron and Shell. The retailers all put their own additive packages in before shipping it to the retailer. What you are really saying is that you think Valero Retail's additive package is inferior to Shell or Chevron. I don't really have an opinion on that. I personally think they are all safe for our motors. All that said, I will probably keep buying mostly Shell because it is the closest station to my house.

I get 22 mpg average.

I get better mileage in my 6.0 liter Cadilllac Escalade. LOL http://rennsportsystems.com/letstalk...twin-ignition/

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Well if thats normal, then mines normal. I always seem to be putting in over $40 worth of juice. A couple of times a week. I don't really check my milage or statistics.

checked mine again, 23-24mpg hwy @75mph. can get 17mpg in town if I want to, but I don't want to, 15 mpg way more exciting.

12mph is better again hehe

Just did a round trip Rockford, IL to Des Moines IA and back. Avg. of 26.4 for the trip and that was some driving at 80 to 85.

i think that it's just my car, loves to suck gas. I drive like a freakin' granny shifting at 3500 and driving at 74mph in the freeways to save gas i still get the nasty low mpg

I have gotten as bad as 9 and as good as 28, depends on how your driving...

I kept getting around 8 MPG for the past couple of days... Then I realized driving on the track between 5k-7k RPM didn't help my gas mileage much. Fortunately for the 75 mile trip home I was back up to about 24 MPG.

Over 17,000 miles my computer says 18.4, awesome. If it was any better i'd be worried. No, I never zeroed it, not once.

I just had plugs, coil packs, and O2 sensors replaced. Picked up about 2 mpg in both city and highway driving. Go figure.

Driving up to Thunderhill raceway in some traffic and some deserted areas, I got 26.5 on the way up and 27.5 and the way back (less traffic). On the track I got 12.5. I wasn't pushing to hard as it was the first time taking the car there. But all that being said it didn't buy it for the mileage.

Just returned from a Seattle to Portland trip for a track day followed by a couple of work days in the Rose City. The combined hwy/city part averaged 20mpg with about 75% of that being highway miles. I burned 7/8 of a tank of gas on track day and got about 9mpg pushing as hard as I could go.

avg. 25 mpg workaday commute 50 miles roundtrip 40 of which is highway

I've gotten 24 MPG on a long day of cruising with top down and 50 MPH nominal speed on secondary roads.