Are there mods to your engine because my engine is all stock and it runs fine on regular gas ?

 

I usually run the DIC on the Avg MPG average display just to see where I'm at with a tank of fuel but that isn't where I came up with my 31.65 MPG gas mileage figure.
At each fillup I reset trip odometer 1 to zero. I keep a log book in the glove box (learned this from my Dad who was a USAF pilot). I've been doing it since I bought my first new car in 1972.
I log the following:
Date/Mileage/Item/Cost/Remarks
I do this for everything I do to a vehicle including each tank of gas.

For fillups in the item column I write "Gas" then put the # gallons it took in parentheses. Next to that I log the miles from the trip odo (I have verified that it is in fact accurate).
A typical refueling log book entry would look like the following:
2/1/13 50001 Gas (14.95) 356.1 $48.72

So when I say I got a 31.67 MPG highway tank it was computed by dividing the number of miles driven on the tank of fuel by the number of gallons taken at fillup. In my case, this is a no bullsh*t, mathematically computed average of a tank of gas on a road trip. Did the math the way Mrs. Smith, my 5th grade teacher taught me how to do it. I got this mileage driving through Illinios, Kentucky and Tennessee. I had the top up and A/C on and the cruise set at 7 or 8 over the posted speed limit. On the trip through Illinois the speed limit was 65 and I had the cruise set at 72. I was running 32 psi in my front tires and 30 psi in the back tires.

I've gone to this level of detail to attempt to explain to you that this is true scoop, and despite your comments to the contrary, nobody here is blowing smoke up anyone's backside regarding the mileage capabilities of these cars. So, if you want to pick apart those of us who are stating they are getting great mileage with their C5s and you are not, you might want to take a look at why you're not also achieving those numbers.

Remember, your actual mileage may vary......

 

Depending on where I am when I need gas, I run either Mobil 93 octane, Sunoco 94 octane, both with 10% ethanol, but with a dosage of Lucas Oil's "ethanol neutralizer". Or, I can also access a "private label" 91 octane, with 0% ethanol. And in all honesty, the cars seems to run the same, no matter what's in it....

 

Jet engine fuel (if I could get it). Hotter the better.

 

Umm, Jet fuel (JP4, JP5) is nothing more than highly refined kerosene, despite what Wile E Coyote seems to believe

 

Mine is totally stock under the hood.