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Originally Posted by Skruffy
Well, I don't know what the heck is wrong with my daily driver. I have a 97 C1500 with a 5.0 liter and when I'm on the highway 75-80, I only get a little over 14. Now, before I bought new tires I was getting a little over 15, but still, I don't see how my mileage could be so much less.
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were these tests done "back to back"? a different fuel blend can make a difference. the fuel suppliers change the blend quite often. even going to a different station can make a difference.
for the record I used to have an '80 K20 with a 355, 0.120 domes, 74cc heads, Crower 00210 cam (I forget the specs), weiand stealth intake, stock HEI with Hypertech coil and both heavy springs and no vac adv., and a HIGHLY modified Holley 4776, 31-10.5-16.5 tires, 3.73 gears and a Muncie SM465 trans. I got between 17 and 18 MPG @ 75 MPH. oh, BTW, I was running 14* initial and 91 octane Amoco silver. it was a wonderful combination, at 60 I was at about 1/2" throttle and the engine just wanted to run away (if you know what I mean).