i cant figure out why but my mpg is dropping in my 02 silverado. its got a 6.0 in it, which i no eats gas. i was getting 13-13.5 and now im getting about 11. im not romping on it, and i changed my oil recently. any one have any idea what could be the cause? i noticed black on the inside of my exhaust tip, which im pretty sure means its burning more oil than it should? byt correct me if im wrong

 

I will share some of my experiences from my 1990 silverado.....

2005: Rebuilt engine...MPG 10-10.5 using cheap gas
2006: After usng 9 octane for about 8 months
2007: Dropped to 10 MPG...did a tune-up and injectors cleaned...back to 11-12 mpg
2011: Same issue as in 2007
2012: I am now getting 12-12.75 mpg on average

can't say for sure why..but my plug wire for port # 6 was melt (tune up mech did not zip tie plug wires) bad cap as well. It as determined that my # 6 port is getting 50% less compression (they say i ned a new engine again)

Anyways...they jery rigged my truck somehow and reset the timing, I have less power...but better gas mileage