MyEmily

I think something is wrong with my P-Car. Crappy mileage!!! After having the oil and fuel filter changed, my mpg went south!!! I used to get 16's in the city and 21 on Hwy. Now I'm getting 12's in the city and 19's on the highway. Same 91 octane gas, same driving habits, what's could have happened? Insights...

PS, got new tires too..

Betternotbigger

Tyre composition and/or tyre pressure. Can make 20% difference

Ecky993

Off subject..from a UK based owner.
Do you really use 91 octane in your 911 ?

My 993 likes 97/98 but will run OK on 95 !! With a reduction in performance!!

rijowysock

We use Ron+mon/2. So our gas numbers are a
little different here than UK.

Porsche says use 93. But in some states 91 is the highest that can be bought.

Giacomo

On pure highway driving you should be getting in the 27 mpg range, at say 75 mph.

I get mixed city/highway of around 21 mpg and pure city, others report 15/16 mpg, but I've never done a full tank in the city.

Jim 'n' SC

Somethings not right. No way you should be getting 21 on Hwy.

Dave07997S

91 (r+m)/2 = 95 RON...

93 (r+m)/2 = 98 RON

If I really baby the car, never exceed 3k rpm I can get 17 city in the car and 25 hwy. Once you dig into the throttle though that goes way out the window.

dave

MichaelL

27 mpg on the highway seems very high. I never had instantaneous values over 22-23 mpg. Mixed driving generally 15-17 mpg, never close to 21. Strictly heavy traffic/around town can be 12-14 mpg.

RonCT

Bad gas or different tires? You mentioned you got new tires, but are they the same Porsche N-specification you had? I've read where Porsche and their OEM tire makers have been working hard at lower rolling resistance compounds to enhance MPG. I would assume that if you use a "different" non-N tire, you could see reduced efficiency.

I think I have about 7k on this 09 now. Overall MPG is about 21 combined with about 50/50 city / highway. I see a peak of low 30s on the highway.

JMAGOLAN

With 35K on the odometer of my 2006 C4S Cabriolet, I typically get around 17 MPG around town (limited highway driving) and 23 to 25 MPG in mostly interstate driving. I did exceed 30 MPG a few times driving from Raleigh, NC to Denver, CO last summer for the PCA Parade, with mostly 26 to 28 MPG on that trip (all interstate driving). I would be concerned with numbers like yours, too. Have your mechanic check to be sure you don't have a loose sensor wire (speculating here) or some other problem. Good luck and please let us know how it turns out.
Jerry

yemenmocha

Always 16 mpg for the tank. Lot of spirited driving and very little highway "cruising".

RollingArt

I get about 19.5 mpg combined driving.

Sounds weird your mileage went down like it did.

What kind of tires were installed? Seems like the most likely culprit.



Phil

Edgy01

Sadly, we in Kalifornia always take a hit on fuel and mileage. We pay the most for gas and only get 91 octane. As a result, our mileage is worse than that experienced by someone in another state. The only variable that seems to be the culprit may be the tires. Pump up the pressure a bit--but not so they're harsh.

JW911

There's a setting in your PCM that you are supposed to reset when you install new tires. I believe it has something to do with the new tires' being slightly larger in diameter due to being unworn. I don't know all the particulars about this, but I would check it out.

Ironically, I just installed new tires recently and had forgotten all about this. But just today I was scrolling around the PCM and stumbled across this new tire reset feature. Come to think of it, my average MPG is 2 or 3 less than usual lately. Hmmmmm. Check it out...

MyEmily

Thx...I've got new PS2 and took it on a long trip. Mileages is improving, maybe it's brand new tires. LOL! already got a screw on it. Luckily, it's brand new! No through puncture.. Anyway, will test out the mileage again this weekend.