2000 Denali Fuel Economy

**a338566** · 03-06-2008, 04:54 AM

I recently purchased a 2000 Yukon Denali w/ 5.7 vortec and 120,000 Miles. I was anticipating about 14 MPG, but am only getting 11.5 to 12.5. My driving is about 50/50 when it comes to highway/ city. Also it seems to have either noisy lifters or a spark knock i cant get rid of. As with all used cars i buy, i have already switched to synthetic oil, flushed coolant system, new plugs cap and rotor, and had the fuel injectors (system cleaned). Any ideas or is my expectation of 14MPG out of whack?

Thanks in advance.

**Wesman** · 03-06-2008, 11:54 AM

Originally Posted by a338566

I recently purchased a 2000 Yukon Denali w/ 5.7 vortec and 120,000 Miles. I was anticipating about 14 MPG, but am only getting 11.5 to 12.5. My driving is about 50/50 when it comes to highway/ city. Also it seems to have either noisy lifters or a spark knock i cant get rid of. As with all used cars i buy, i have already switched to synthetic oil, flushed coolant system, new plugs cap and rotor, and had the fuel injectors (system cleaned). Any ideas or is my expectation of 14MPG out of whack?

Thanks in advance.

Try doing Seafoam. Buy a can at your local auto parts store, and feed it through the brake booster line with the engine idling. The engine will stumble, stall, and make lots of smoke, but it will clean out the combustion chambers real nice.

The fact that you are getting spark knock tell me that there's probably some carbon buildup in the cylinders thats causing detonation.

***Ed Blown Vert*** · 03-06-2008, 12:10 PM

And I was thinking of getting rid of my Envoy for a Yukon.

**Wesman** · 03-06-2008, 02:24 PM

Originally Posted by Ed Blown Vert

And I was thinking of getting rid of my Envoy for a Yukon.

An newer one I assume?? Obviously the newer LS based engines are going to get better fuel economy than the old 5.7L SB, probably somewhere in the mid to high teens, depending on how you drive.