Buick Enclave gas mileage drops with no warning lights

[fiddleh34ds]

My buddy has a question about his car and is hoping for some insight.

He's getting some really bad gas mileage on his 2015 Buick Enclave only less than 250 miles on a full tank.
The weird thing is, there are no check engine lights or service lights on at all.

He's kind of stuck on where to even start looking. I want to help him, any ideas what could be causing such bad mileage without throwing a code?

 

[Kayleb]

Maybe put some fresh plugs or just scan it with a scan tool showing fuel trims

 

[JohnBuick]

My buddy has a question about his car and is hoping for some insight.

He's getting some really bad gas mileage on his 2015 Buick Enclave only less than 250 miles on a full tank.
The weird thing is, there are no check engine lights or service lights on at all.

He's kind of stuck on where to even start looking. I want to help him, any ideas what could be causing such bad mileage without throwing a code?

A 2015 Enclave with less than 250 miles on a full tank is definitely concerning, especially with no codes. I suggest rule out the simpler stuff first. I'd start by checking the air filter! A clogged one can really choke the engine and kill your mileage. Also check if the spark plugs are worn-out since that could cause incomplete combustion and poor fuel economy. Both are cheap and easy fixes!

After that, look into the O2 and MAF sensors. They can start to fail and throw off the air or fuel mix without being bad enough to trigger a check engine light. A bottle of MAF cleaner is a good thing to have on hand. Also, how's the exhaust? Any unusual smells? A clogged catalytic converter is a less likely but still possible cause.