2007, 6.2l Yukon Denali

Last week I had to change the headlight lamp on the passenger side. I had to remove the air filter box to get at the darned thing. I put everything back together and everything seemed to be working just fine. Except for one little detail, the gas mileage dropped from 15 to 16 mpg to about 13 to 14 mpg. This doesn’t sound like much, but, when I towed our travel trailer the mileage dropped to 9 mpg (from around 13mpg before I touched anything). Any thoughts on what I might have done to create this situation???

Is your check engine light on? Depending on how the air intake is set up, you might have accidentally broken or unplugged an intake air temp sensor or something similar. Make sure the air intake is put together and shut properly.

You were right. I had not tightened the clamp that connects the air filter box to the air intake. Everything is back to normal. :slight_smile: