Very low mpg, help plz

[Mike689]

Hello I just bought a 01' Boxster S about 2 weeks ago. I changed the oil a few days later and I drive at around 3k rpm. I'm still only getting about 16 mpg and I drive mostly on the freeway. Am I doing something wrong or is it the car? and how do I fix it? thanks!

[JayG]

Did you have a PPI done before you bought it?
Is it running properly?

Changing the oil has very little to do with MPG. Yea, maybe a little impact, but...

What RPM are you shifting at?
Are you in 6th gear at freeway speeds?
how fast are you going
uphill? downhill?

Also without pics, the car is not real

[Mike689]

Originally Posted by JayG

Did you have a PPI done before you bought it?
Is it running properly?

Changing the oil has very little to do with MPG. Yea, maybe a little impact, but...

What RPM are you shifting at?
Are you in 6th gear at freeway speeds?
how fast are you going
uphill? downhill?

Also without pics, the car is not real

No PPI. I'm shifting at around 3.2k and I use 6th gear on the freeway. I'm driving at around 25 using 3rd Downhill also. I'm driving around 70 to 80 on the freeway.

[JayG]

was the MPG better before you changed the oil?

[Mike689]

Not really sure I didn't have it long enough and I only filled the tank once.

[BYprodriver]

If your check engine light is off & in working order, (insure it is on when you 1st turn on the ignition switch) it may be injector or sparkplug related. Put injector cleaner in gas tank & then fill tank with Chevron premium. This is designed to clean fuel system & combustion chamber in cylinder heads. The debris that is cleaned can get past piston rings into the oil sump so you should change oil soon after that tank of gas is gone. Replacing the sparkplugs should improve efficiency also. Search this forum to decide which oil to use.

[Mike689]

Originally Posted by BYprodriver

If your check engine light is off & in working order, (insure it is on when you 1st turn on the ignition switch) it may be injector or sparkplug related. Put injector cleaner in gas tank & then fill tank with Chevron premium. This is designed to clean fuel system & combustion chamber in cylinder heads. The debris that is cleaned can get past piston rings into the oil sump so you should change oil soon after that tank of gas is gone. Replacing the sparkplugs should improve efficiency also. Search this forum to decide which oil to use.

The check engine light is ok and I changed the oil almost 2 weeks ago. I used Mobil 1 0w-40. I also have lucas oil injector cleaner I can use, I don't know why I didn't think to put some in the tank. I haven't been using chevron gas though it's expensive. Since I got the car I've been using arco 91 premium.

[BIGJake111]

Originally Posted by Mike689

The check engine light is ok and I changed the oil almost 2 weeks ago. I used Mobil 1 0w-40. I also have lucas oil injector cleaner I can use, I don't know why I didn't think to put some in the tank. I haven't been using chevron gas though it's expensive. Since I got the car I've been using arco 91 premium.

What's your elevation? Can you not get 93?

[BYprodriver]

Originally Posted by BIGJake111

What's your elevation? Can you not get 93?

In CA!, that's more illegal than pot!

[BYprodriver]

Originally Posted by Mike689

The check engine light is ok and I changed the oil almost 2 weeks ago. I used Mobil 1 0w-40. I also have lucas oil injector cleaner I can use, I don't know why I didn't think to put some in the tank. I haven't been using chevron gas though it's expensive. [B]Since I got the car I've been using arco 91 premium.

[/B]

Bingo!!

[Mike689]

Originally Posted by BYprodriver

[/B][/U]

Bingo!!

Does it really matter that I'm using arco?

[BIGJake111]

These cars can get anywhere from great mileage to low. If you are in 6th on the highway and mostly doing highway driving the mileage should be better than 16 though. I notice a significant difference when going from city to highway driving in the boxster, a much larger difference then any other cars i drive.

How are you factoring the mpg? Does your car have a computer or are you figuring your mpg manually?

[Mike689]

Originally Posted by BIGJake111

These cars can get anywhere from great mileage to low. If you are in 6th on the highway and mostly doing highway driving the mileage should be better than 16 though. I notice a significant difference when going from city to highway driving in the boxster, a much larger difference then any other cars i drive.

How are you factoring the mpg? Does your car have a computer or are you figuring your mpg manually?

I've been doing it manually. Even with city driving I don't think it should be 16mpg.

[911monty]

Mike; Are you smelling fuel around your car? Any leaks? You should have a CEL lit if that much fuel is being unburnt in the engine and your Cats should be glowing red! Why are you shifting at 3.2k strange engine noises? I would wonder if an exhaust valve is stuck open, but like I say your cats would not like it. NOT those cats!

[Mike689]

Lol I don't have 93 in my area and I think CA it doesn't go over 91. It shouldn't matter though because the engine has the octane knock sensor thing right?

[JayG]

No, I use ARCO gas sometimes and it is not a problem
Mostly I put in VONS/Safeway or Costco and its 91 octane. Other than a few odd places, 91 is the max around. There is one station that has 100 and its around $9.00/gal. Its in a very wealthly area and there are lots of supercars there

Lets not make this in to a What Gas should I use thread

In my 04 S I get around 18 city, 20 mixed and 28 Hwy
I have a reasonably heavy foot and generally am 10-15 over the limit

That is all based on the onboard computer

[particlewave]

3.2k is really low. Keep your shifts between 4k-5k+. At about 5.5k, that engine really sings.
Even with that said, you should be getting better mileage.
My 2.5 gets roughly 20 city, 25+ highway, even on 91 octane.

[Mike689]

Originally Posted by particlewave

3.2k is really low. Keep your shifts between 4k-5k+. At about 5.5k, that engine really sings.
Even with that said, you should be getting better mileage.
My 2.5 gets roughly 20 city, 25+ highway, even on 91 octane.

On 6th gear going 65mph the RPM is around 2.5k. Should I be using 5th gear then?

[911monty]

Originally Posted by Mike689

On 6th gear going 65mph the RPM is around 2.5k. Should I be using 5th gear then?

Yes; Listen to your engine and feel the pressure you are using on the throttle. The engine will communicate back to where it wants to run. You will have much better results. I have driven my 2.5 into So CAL down the 215 rarely using 5th gear and have gotten 32 calculated freeway. I believe you are so low in RPM the knock sensor is retarding the ignition timing. Try keeping at 3.2k +. I don't think your plugs are an issue since you just bought car so had to pass CA smog. Of course new plugs are always good.

PS; I used to have an air cooled 911 with weber carbs hat would load up below 3.5k. This was during the famous 55mph speed limit days. I used to have to shift constantly between 2nd and 3rd that car really hated that speed limit. Now at 90 Yahoo!

[Mike689]

Originally Posted by Fintro11

how is your air filter / tire pressure?

The tire pressure is fine I checked it 2 days ago. I should probably change the filters though.

Originally Posted by 911monty

Yes; Listen to your engine and feel the pressure you are using on the throttle. The engine will communicate back to where it wants to run. You will have much better results. I have driven my 2.5 into So CAL down the 215 rarely using 5th gear and have gotten 32 calculated freeway. I believe you are so low in RPM the knock sensor is retarding the ignition timing. Try keeping at 3.2k +. I don't think your plugs are an issue since you just bought car so had to pass CA smog. Of course new plugs are always good.

Damn I'm such a newbie lol. I've driven a manual car before but it wasn't a sports car and this my first car with manual. So I've been lugging my engine for like 3 weeks I hope I didn't screw things up too bad.