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Old 03-31-2012, 09:58 PM   #1
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Newbie - horrible gas mileage

Hello fellow boxster owners!

This month I picked up a 2008 boxster s w/ 2700 miles!! And I finally experience what fun it is driving a convertible! Was in the market for a cayman, but the wife wanted a convertible.. So far I have driven 400 miles, loving every minute, but I seem to have filled up like 3 times!! I know what you thinking, but I am not really pushing the car, shifting normally around 3-4.5k rpm and the computer is telling me I'm avg 15.6! I think it should be higher, and not sure what the issue is, I figure I ask first before I visit the dealer, any input would be really appreciated.

Mods are 19" wheels, borla exhaust.. I think that's all.

Thanks!!

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Old 04-01-2012, 02:50 AM   #2
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Gas will be among the cheapest things you put in it, I couldn't tell you the fuel economy of my 986 because I never took any interest. Keeping the RPM's up to enjoy a Porsche is going to consume fuel, I suppose if you up-shift and keep the RPM's purposely low you might eek a few more out of it. A tune up is always a good call, tire pressures, air filter, plugs could have a slight impact, then again it's not meant to be a Prius. When my pal told me his BMW K bike was far less than 50 mpg I felt pretty good about what Porsche has achieved.
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Old 04-01-2012, 03:55 AM   #3
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where were those 400 miles? open road cruising or around town/short trips? you'll get better mileage on long open-road trips over short stop and go trips. keep the RPMs up and enjoy the car. slow and steady is not the way to go in this one...
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Old 04-01-2012, 04:53 AM   #4
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I have put almost 5k on mine since Jan. Some short spirited and two 7 hour trips with wife and mileage is about the same both ways. The long easy drives are around 19-20 and other times 17-18. Computer over all says about 18.
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Old 04-01-2012, 06:25 AM   #5
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Welcome to the Forum - you can learn a lot of stuff here. 99.9% of it will apply directly to your 987, as under the skin they are almost identical. Still there are a few things (mufflers come to mind) that are not directly interchangable. You may also want to check out the Planet 9 forum, which is mostly Cayman and 987 Boxster owners. I try to stay on both.

Agreed on the mileage thing - my 986S mileage is poor because I just can't keep my foot out of it, and I still can't figure out why we have a 6th gear.
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Old 04-01-2012, 07:14 AM   #6
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My daily driver (07 Mustang conv) gives better mileage reporting than my 06 Boxster S, so my observations are based on that car, though the basic idea is the same...

I can meet or often exceed the rated mileage on that car if I drive conservatively - easy starts from red lights, keeping steady speeds instead of pushing and braking, pushing and braking all the time. I've actually hit 33.5 mpg this way with no crazy modifications. I don't idle the car unnecessarily, and I keep my speed to around 65 on the highway ( the cars sweet spot - above or below that and consumption goes up fast)

If I drive to keep up with traffic, the way people in my area go, my mileage instantly drops to 20 to 22. I don't want to think about how much fuel they're guzzling down in their SUV's and big trucks!

SO much depends on how hard/often you push those pedals.

Back to your new boxster... If it has an aftermarket exhaust, then I'd wager it has a hot chip in it too, both of which will often eat into your mileage. Then there's the way you drive it. It IS a Porsche after all! I'm not surprised by what your getting.

As mentioned, give it a tune up and see where that takes things, but I think you're about where you should be.
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Old 04-01-2012, 07:56 AM   #7
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Ixnay on the early upshifting! Lugging these engines is a death sentence for them. Keep the rpm's up and enjoy the car for many years. Screw the gas milage - if that's important to you then you may have bought the wrong car and perhap a TDI Jetta might be a better choice.
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Old 04-01-2012, 08:25 AM   #8
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Well OCZ welcome to the forum. I have a 2001 Boxster base and am currently getting around 20 mpg - that is Imperial gallon, not US gallon but that is close. Also we have cool weather still. Once spring comes and I get out in the country more than 27-30 mpg is possible. As my daughter said to me, you did not buy a Porsche to get good gas mileage. As the above poster says, keep up the revs and dont lug it. Enjoy the Boxster symphony music!
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Old 04-01-2012, 08:46 AM   #9
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I do enjoy the sound of the engine and exhaust... i have yet to turn on the radio in the car, my whole point of the original post was that, MAYBE there is something wrong with the car?? Gas mileage is not all that important to me, as my other car SUV gets around the same, but rather all things being equal... why is my rather new car getting such bad gas mileage... Its very sunny today, i'll take the top down, and try to keep up the revs and report back... I would love to keep the revs up, but in city driving is not alway convenient.. Thank you all of great inputs! :dance:
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Old 04-01-2012, 08:52 AM   #10
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1) it's a sports car, gas is the cheap part 2) I came from an Audi S4 that got 14mpg on a good day so the 16mpg I get on average from my Boxster S feels good.

Cliffs notes: you're getting "bad" gas mileage because the pedal on the right is addictive
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Old 04-01-2012, 11:43 AM   #11
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Over the last 7 years of ownership my typical mileage looks like this:

Open highway- 30mpg
Average mixed driving- 22mpg
Track days- 12 mpg

Yes the right foot has everything to do with mileage assuming the car is properly tuned and in good working order. A heavy set of aftermarket wheels can adversely affect the mileage a lot also.
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Old 04-01-2012, 11:56 AM   #12
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Welcome OCZ. Based on the description of your driving, I'd say there's something amiss with your S. My Box gets 19 in town and 26 hwy. You might want to see if there are any codes present that can give you a hint.
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Old 04-01-2012, 11:59 AM   #13
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Quote:
Originally Posted by oczdreaming View Post
I do enjoy the sound of the engine and exhaust... i have yet to turn on the radio in the car, my whole point of the original post was that, MAYBE there is something wrong with the car?? Gas mileage is not all that important to me, as my other car SUV gets around the same, but rather all things being equal... why is my rather new car getting such bad gas mileage... Its very sunny today, i'll take the top down, and try to keep up the revs and report back... I would love to keep the revs up, but in city driving is not alway convenient.. Thank you all of great inputs! :dance:
Well I like to keep the revs up while living in the city, I am basically restricted to 1,2 and 3 gears. 4th gear I would be lugging it too much. Staying in 1-3 gears keeps me down to city speeds but I certainly dont redline it. High revs does not necessarily mean high speeds. I can understand why some folks buy tiptronic especially for the city but I do like shifting gears especially when you have a great transmission like the Boxster
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Old 04-01-2012, 01:36 PM   #14
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Originally Posted by husker boxster View Post
Welcome OCZ. Based on the description of your driving, I'd say there's something amiss with your S. My Box gets 19 in town and 26 hwy. You might want to see if there are any codes present that can give you a hint.
I've got an '01 S, and get mileage comparable to this. Unless you're really flogging it hard, or spend a lot of time in stop and go traffic, I'd agree---your mileage seems on the low side.
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Old 04-01-2012, 06:38 PM   #15
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Ok, Just got back from a 100 mile trip, to newport beach and back... What a blast, i'm actually tired.. LOL of the 100 miles, I would say 30 miles are highway miles avg 80mph, and for the 100 miles I got 17 mpg... I think something is wrong... the codes I would have a dealer look at correct? thanks for the comments.
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Old 04-01-2012, 08:17 PM   #16
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ocz...
Are you getting the info from the computer or are you filling the tank to the brim, driving the 100 miles and then topping off the tank, using the maths to calculate the mpg? Thats the correct way of calculating.
Computer generated figures can be misleading at best and damn wrong at worst....
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Old 04-02-2012, 04:59 AM   #17
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Originally Posted by oczdreaming View Post
Ok, Just got back from a 100 mile trip, to newport beach and back... What a blast, i'm actually tired.. LOL of the 100 miles, I would say 30 miles are highway miles avg 80mph, and for the 100 miles I got 17 mpg... I think something is wrong... the codes I would have a dealer look at correct? thanks for the comments.
What you are getting sounds about right. For starters, you are in an "S", not a base model. You are driving 80 mph for 30 miles out of 100. That suggests that 70 miles were city miles. Both 80 mph and city miles are notorious for bad gas mileage. Then you talk about how you had a blast, that sounds like heavy acceleration, and of course that's bad for gas mileage, too.

For frame of reference, my car is an 08 base model and I get 23 around town and 27 on the highway ... but the base model has a smaller engine and I tend to drive a little slow. Also 60-65 mph will use a heckuva lot less gas in ANY car than 80 mph. And even I can easily drag my own gas mileage down into the teens with a heavy foot, trust me.

I think if you try driving 100 miles at a steady 60 mph, you'd probably get 25 even in your "S" model. I suggest you do that test before you go to the dealer. The $$$ you pay the dealer to "fix" what ain't broke would buy a lot of extra gas.
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Old 04-02-2012, 07:23 AM   #18
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You may want to have the car checked out by someone other than the dealer) to see if the ecu has been tuned for the exhaust it has. It's possible that it hasn't, and that could affect mileage for sure. You do have to accept that the car's not going to be terribly efficient, and the ill effects of driving the car like an economy car at low rpms ae not worth squeezing out a few more mpgs. If the car needs a tune it could help you gain a few mpgs and smooth out the fuel map. The car's fun, for sure, but like others, I don't go beyond 3rd gear in the city, and I don't use 5th (or 6th in your case) until I'm above 70mph. My old base gets a pretty consistent 20.5 mpg, by my own calculation, not the car's, with mostly city and turnpike driving, but it's a much smaller engine than your 08 S, even if it's from an era of much lower efficiency compared to today's cars, that still likely plays a part.

If you can, try to make your next long trip mostly highway, and try to bring it down 10mph on the highway to 70mph. 10mph makes a huge difference in fuel economy no matter what you're driving, trust me.

You may also want to try filling up with the high octane from a few different gas stations and see if there may be a brand that your car likes more than another.
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Old 04-02-2012, 09:47 AM   #19
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Originally Posted by johnsimion View Post
What you are getting sounds about right. For starters, you are in an "S", not a base model. You are driving 80 mph for 30 miles out of 100. That suggests that 70 miles were city miles. Both 80 mph and city miles are notorious for bad gas mileage. Then you talk about how you had a blast, that sounds like heavy acceleration, and of course that's bad for gas mileage, too.

For frame of reference, my car is an 08 base model and I get 23 around town and 27 on the highway ... but the base model has a smaller engine and I tend to drive a little slow. Also 60-65 mph will use a heckuva lot less gas in ANY car than 80 mph. And even I can easily drag my own gas mileage down into the teens with a heavy foot, trust me.

I think if you try driving 100 miles at a steady 60 mph, you'd probably get 25 even in your "S" model. I suggest you do that test before you go to the dealer. The $$$ you pay the dealer to "fix" what ain't broke would buy a lot of extra gas.
I dunno...yours (OP) still sounds low to me. For my quoted highway mileage (~26 mpg) I was doing 80 or better much of the time. (I was on I80 in Pennsy...I started out a little slower than that---maybe 75---then found myself being passed by semis that were doing at least 80. I sped up accordingly ) I didn't use the car's computer readouts---my calculations were based on actual gallons pumped and miles covered.

Your car IS equipped with a bigger engine, and weighs in over 100 lb heavier, but I'm guessin' part of that is offset by tweaks resulting in improved efficiency. And Husker's Box is pretty similar to yours...
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Old 04-02-2012, 09:54 AM   #20
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Originally Posted by johnsimion View Post
What you are getting sounds about right. For starters, you are in an "S", not a base model. You are driving 80 mph for 30 miles out of 100. That suggests that 70 miles were city miles. Both 80 mph and city miles are notorious for bad gas mileage. Then you talk about how you had a blast, that sounds like heavy acceleration, and of course that's bad for gas mileage, too.

For frame of reference, my car is an 08 base model and I get 23 around town and 27 on the highway ... but the base model has a smaller engine and I tend to drive a little slow. Also 60-65 mph will use a heckuva lot less gas in ANY car than 80 mph. And even I can easily drag my own gas mileage down into the teens with a heavy foot, trust me.

I think if you try driving 100 miles at a steady 60 mph, you'd probably get 25 even in your "S" model. I suggest you do that test before you go to the dealer. The $$$ you pay the dealer to "fix" what ain't broke would buy a lot of extra gas.
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