I have a 97 CC Sport+ 4x4 318 Auto and I've gotten 10 city/ 13 hiway since
the day I bought it. You should expect with bigger tires and the same gear
ratio to lose gas mileage. Your truck has to work harder during
acceleration and going up hills. Also, you have a 3 inch lift, that's more
wind drag. I have dual exhaust on my pickup as well, and it didn't change
my mileage any.
Chris Ryan wrote:
> Hey everyone, my name's Chris, long time reader, first time poster. I
> own a beautiful Black '99 CC Sport+ 4x4 318 Auto. I've added a GoRhino
> Grill/Brush Gaurd, Westin Side-Step Bars, WAAG Tail-Light Gaurds, GTS
> Blackouts F & R, 180 TS, K&N Drop-in, Modified the intake to the stock
> box, Champion Truck Plugs, Flowmaster 2 chamber, Extang BlackMax
> Tonneau, Rancho 3" lift, 32x11.5 BFG AT, running premium most of the
> time, with currently around 18,000 miles.
>
> I love everything about the truck, except the one and only problem I've
> had with it since I brought it home. It gets 9 city/14 hwy. Up until
> around 10000 miles it got 14 city/19 hwy. The only mod that I did around
> that time was add the Flowmaster, and I wouldn't have thought that
> would've brought the milage down that much, if at all. I've had it to
> all three of my local "5 star" service centers a total of seven times
> and I got at least as many different answers, none of which helped or
> was even acurate in my opinion. The explainations ranged from that it
> was normal milage, to something about the sensors needing a certain
> amount of back pressure and the addition of the Flowmaster changed that,
> to the inch larger tires. It's obviously not normal, the inch larger
> tires should produce the same if not better mpg, I'm not sure about the
> Flowmaster though. For economic reasons I didn't change the diameter of
> any of the pipes, I just swapped out the stock muffler for the
> Flowmaster. Would that have anything to do with it? I guess my next step
> would be to start hunting for a leak, she sleeps in a garage and I've
> never noticed a fuel odor, so I doubt that's it either. I also thought
> I'd put a presure gauge on the test port on the fuel rail and make sure
> I'm getting proper pressure from the tank to the injectors. If I get no
> results from that I might try putting an OEM muffler back on, but I
> don't want to do that. She runs like a champ though, that's really the
> most confusing thing, I'm constantly dusting stock trucks and cars of
> all makes and models, and I can leave a nice trail of rubber behind when
> I heat the tires up. So it doesn't seem like she's starved for fuel or
> leaking any, but she sure gobbles it up.
>
> Any suggestions or comments would be greatly appreciated.
>
> Chris
> Portland, OR
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