My 99 suburban 1/2 ton with 5.7 is getting 10-11mpg, city or highway. It has a 3"lift, but my friends with the same lift get 16mpg's still. I have a cold-air intake, a Superchip performance chip, I have tried setting the chip to economy and performance, neither help mpg's in the slightest, I have a performance muffler, a new high-flow catalytic converter, a new fuel system (the $1000 complete spider-shaped fuel delivery thing), complete new tune-up with performance wires and plugs, a fresh fuel filter, fresh belts, EVERYTHING! It runs great, but seems a little lacking in power, maybe its normal to lose significant speed going uphill, but most of all, I haven't gained so much as a 1/2 an mpg with all this stuff. Every fluid in the truck is fresh, it runs cool around 140, but 10mpg's! HELP!
have the same problem?
Wednesday, March 24th, 2010 AT 5:44 PM