So this is the 3rd 911 I have owned since 2007. My current 2007 CS convertible is getting roughly 13.5mps city with non aggressive driving. My previous other 911's were generally in the high 16' and low 17's. I am wondering if this is norm?

 

17 for me, mix of city highway, mostly city during the week.

 

2006 C2S 17.8mpg consistently. Mix of highway, city. No complaints

 

06 c2s. getting 19 average. mostly highway daily commute

 

Any ideas what could be causing this?

 

Mods, Manual or tip, sport mode engaged, highway/city, traffic?

 

Only mod is the gundo hack which I also had on my previous C4S. Its a manual trans and I dont use sport for daily driving. I live in L.A. so yes, usually somewhat traffic.

 

In my C4s I usually got around 17-19 mpg consistently, traffic or otherwise. I generally achieved 13 mpg while spending a day at the track. Your results seem very low for normal driving.

 

My thoughts exactly. Hoping someone here experienced the same and would be able to point me to a cause.

 

19.8 mpg for me. Not much city driving for this car I've briefly touched 26mpg when traveling long distances on the highway. It dropped down the second i got off the highway and into stop and go traffic.

I drive the car around at 3k rpm when cruising around

 

Local commute, just under 17mpg. Just did a 6hr road trip - ~23mpg @ 80-85mph. On the return trip - ~21mpg @ 90-100mph.

 

City driving I get 15-17 mpg.

 

On my C2S with Headers, exhaust, tune, 6 Speed, i barely get 11MPG city driving. My commute is less than 2 miles.

 

For sake of your car and your endorphins start taking long way home

 

You have to be careful. The poster to whom you are replying to is in GA. Driving conditions there may not be like they are in LA. I've been to LA and and driving conditions there are like no where else I've been.

Also, the GA driver might have access to a higher octane grade of gasoline. All you have in LA (and all we who live/drive in CA have access to) is 91 octane. I can tell you running 91 octane gasoline accounts for some loss of fuel economy. There is also the difference in winter vs. summer blends. This different blends of gasoline in winter vs. summer -- I think an only in CA thing -- can and does affect gas mileage.

My experience over the years is usage plays a big role in a car's gas mileage, all other things being equal, which they seldom are.

About all you can do is be sure you are buying fresh gasoline. Buy from a busy station. Buy the correct octane grade (or as close as you can get, which is 91).

Be sure the tires are properly inflated. Do not overinflate but do make sure they are inflated to the proper PSI. Buy an accurate tire pressure gage and be sure you get both sides at the same pressure.

If tire wear across the tread faces is uneven this is an alignment problem. A bad alignment that causes tires to wear unevenly is an alignment that can negatively affect a car's fuel mileage so have this alignment addressed.

The engine controller (DME) is pretty good about properly fueling the engine. It should be that's its job. If the engine were using too much fuel the DME would have to be adding this extra fuel and if it had to add too much for some reason it would flag a CEL.

In short I think your car's difference in fuel ecomony can be explained by the normal variation there is between two different cars expecially two different cars being used in two rather different environments.