I thought the C4 tank was smaller.

 

Imperial Gallon - I love that!!!

 

still skeptical...
Stock numbers at the time were 17/25 mpg.
That perfectly apes mine, and I'm lowered w/ stock intake (just like our C4 in question)

...and a K&N intake resulting in a near 50% bump in mileage?
Them's some mighty lean fuel flows in a 964.
But who knows? Maybe you've got one of them freak 'golden' engines off the assembly line.

 

Porsche 917, there's also Imperial;

threads
nautical mile
fluid once
pint
quart
hundred weight
ton

and the Imperial gallon is based on measuring.............. 'Ale'(beer)! Which I believe was the first thing the founding fathers asked the natives for when arriving at Plymouth from Plymouth.

 

My brother's Corvette (a 7.0 liter C-06) at 70-75 MPH turns over at 1500 rpm. My 90 C2 is turning 3,000 rpm at the same speed. Both are getting 25 MPG. We need a taller gear to get the RPM's down to 2,000 at cruise speed and, maybe, reach 30 MPG.

 

THOUSANDS of cruising miles in my '92 C4 from '98-'02 when I didn't tow and would run up to Thunderhill or down to Buttonwillow or Willow Springs. About as untaxing a freeway ride as you could get. 75-80 was my cruising number, usually got right about 23 US miles per US gallon.

Now my friend's '92 C2 targa would get about 25 the couple of times I took it on similar trips.

 

On a recent trip from KS to NC, I got a solid 25 MPG with the A/C running almost all of the time. Not sure about tire pressures, but airing the tire up, not using the A/C, and slowing down from my 75MPH avg speed (GPS confirmed including road construction traffic) would have probably bumped me into the high 20's.

 

Just returned from a 350 mile round trip, yesterday and got 23 mpg running 80 most of the way. I've tracked my mpg since owning the car, and mpg is 17-19 city, 23-25 hwy. If i get too sporty, the numbers fall a little, but it's very consistent.

 

I think the guy had a break-through idea and put air in his tires!.....yeah, that and the fact that all of his driving is downhill.

Anyone even attempting to get that mileage should have their keys taken away from them, and in some cases it appears that their calculators are also suspect.

 

I forgot to add that I have a cat test pipe so, that might help. Just a weee bit

 

Just to add some German Autobahn numbers, I just did a trip to my uncle (200 miles) pretty much flat out and I did around 12 mpg's - but it was a hoot!!!

 

No way, and no way a K&N filter makes a difference at economy cruise. The throttle plate is barely cracked, and all the pressure drop in the intake system occurs there. Perhaps the tire size was lowered so that the odometer reads a lot of extra miles not traveled.

I have seen 25 - 26 MPG, GPS verified, running 80 MPH on the freeway using 93 octane pump gas. Tires were new, inflated to spec, and engine was in fine state of tune but all stock.

 

When I bought my 92 C4 and drove back from Cali to Seattle I was getting 420-430 miles per tank and I was averaging 85-100 most of the way. Thats about 27-28 miles per gallon with the top down.

 

Hard to believe... I get 16-18 around town, 25-26 highway...

35!? wow...

 

Porsche odometers and speedometers are 5% optimistic even with new tires. Correct for those errors, and you are back in the 25 - 26 MPG club. I hate my GPS, but it tells me the truth about both speed and distance traveled. My instruments exagerate both.