After a rough winter ride up the Alcan Highway and rather full service in November at approximately 77,000 miles, I have since been getting VERY poor gas mileage. Perhaps the mileage readout on the PCM might not be accurate. Have any found the PCM miles-per-gallon or kilometers-per-gallon accurate and reliable?

P-Dealership changed oil & filter, air filters, spark plugs and serpentine belt and PCM valve which broke due to brittleness AND one ignition coil towards the back of the engine. What should I do? What parts might be suspect?

Do I need to repalce all of the ignition coils? Are there better spark plugs, for instance, those used in the CT-S that might be helpful? Might I have a bad sensor? Or a poor setting?

The best gas we have up here is 90 Octane. Either Chevron which I almost always use or I could switch to nitrogen enriched Shell. Our gas in winter is oxygenated and costs more than any other state in the USA.

Mine has no mods--yet. It is sill under warranty as it was one of 507 Porsche CPO vehicles sold last year. I have been planning to keep it entirely stock* for a possible long term investment.

I thought of an EVOMS air intake system. In part, because I can buy mesh covers for that pair of venturi air intakes and if those aren't enough, I can put some finer mesh filter material over them when the volcanos errupt.

We have several volcanos accross the inlet. Volcanic ash is messy and can destroy an engine. I've thought of this as a prevention messeaure because if I am far out of town when one erupts, it is too late to act {Order parts, get them and install them} and up here it is best to be prepared. *The EVOMS could easiliy be removed to retore this CT to stock.

I really don't want a loud ride but I have heard that others with Secondary Cat by-pass and/or certain primary Cats (i.e. 100 cell) have more power and better fuel economy.

All winter I have been getting between 8.9 to 12.8 MPG city and 12.8 to 13.8 highway. My SUV is garaged and heated to about 60 degrees F. So, I am not losing gas during long warm ups.

OK, I put my foot in it once in a while (And I pay for it!) but I can't get my MPG up no matter how easy I drive. I'm not too happy with turbo lag but certainly the power helps when towing.

Thanks in Advance

 

the number 1 cause for me is my darn lead foot. I average about 10mpg with my mods. It's been that way for me all along. You pay to play.

 

Yes, I guess it is wishful thinking on my part to get more MPG. Which mods do you find most effective? How about your diverter valves?

 

I have Fabspeed tune, Fabspeed bypass pipes (sound is perfect-not to loud but a true muscle car sound) and cold air intakes. My foot is in it every take off, I drive it very hard, my honest city average is 14.5 and highway @ 80-90 is right at twenty?? Sounds like something else might be wrong???/

 

rather than trying to modify the vehicle, find out what porsche states is the estimated mpg for your cayenne, then bring in your actual numbers to the dealer that serviced it.
I've read 13/18 city/highway for a turbo. if you are getting 15-20% less than that it should be an indicator to the service guys that something could be wrong.
maybe all the coils are cracked, or maybe the service guys didn't even replace the one coil correctly.
you should be able to get your cayenne to baseline fuel performance without adding mods.

 

I typically average 13-15 around town, and 18-20 on the highway, and have gotten 20+ on a couple of road trips. I have secondary cat bypass, magnaflow mufflers, EVOMS filter boxes, and typically drive it lightly spirited with terrible Colorado fuel at 5,000'+. I have found the PCM display to be a bit "optimistic" at times with its display.

 

wow! 18-20 hwy?? How I would love to have that!

 

If you live in the middle of nowhere and your hwy runs don't involve much other traffic then 18-20mpg is possible. I took a drive out of the city and got over 20mpg on some stretches with the cruise control set. In my normal commute, I average 13.5mpg with about 90% of my driving on the hwy. It is the stop and go that gets ya on these 5000lb trucks.

 

THanks! Great response. Are the cold air intakes the EVOMS?

Yes, I think I'd be in the dealership soon to see if they can adjust anything or find anything wrong.

 

You are absolutley correct: I need to get a baseline. Something basic may be wrong. I'll visit the dealer Tuesday and try to consult with thier P-mechanic.

 

It could be your gas, anytime I run something lower then 92/93 Octane my 05 Turbo runs like crap!!

Im currently getting around 440 miles to a full tank of gas....which puts me in the 18-20mpg range.....all mods minus new turbos and driven very hard....

 

 

In Alaska our high octane is only 90!

I have used almost exclusively Chevron but today I filled up with Shell nitrogen enriched--but it's still only 90 octane. That's the best I can get short of buying NAV gas.

Gas up here is expensive. Regular 87 octane costs $3.33. My gas today cost me $3.52 a gallon.