New member with 2013 Sienna minivan
 

In the last month, gas mileage has dropped from 19/26 to 16/23. Anyone have any suggestions?

tire pressure okay, lots of heat/ac use, same driver ?

We need a little more detail. Was the mileage drop sudden or gradual? Are you in an area that experiences real winter? Lower temperatures will lower the tire pressure along with other negative effects. Any recent maintenance done on the car? Change in gas station?

Sudden--within 2 weeks or so. Yes, Michigan, but we have been having unusually warm temps in the 60's and 70's. No recent maintenance. I get gas wherever, often at Sam's Club.

That's insanely low mileage for such a modern car, are you towing a small town behind you? ;)

This is Draigflaig, he's our most tactful member on the whole board. Look for this same post on pretty much every introductory member post. "Your car gets HOW BAD OF GAS MILEAGE???"

I'm in constant disbelief! Lol ;)

American mini vans are only mini compared to full size vans.

Is this your first winter with the car? Winter blend gas will return lower fuel economy. That would likely only explain part of the drop though.

I'd start with checking tire pressures. A low tire can still look full.

Check your coolant level too, a car with low coolant may take longer to warm up to normal operating temperature, when it finally does, it may then overheat causing the fan to kick in sooner and more often.