Here's a video of the Mercedes-Benz Metris USPS vans. They need 91 AKI (premium) gasoline. Actually, that's common with turbocharged vehicles these days. A Chevy Equinox also needs 91 AKI.

https://youtu.be/X7DOQTYeuK4?t=92

My BMW's need 91 AKI, but they only sell 93 AKI in Bubba County, Floriduh. So, I make my own 91 AKI by blending 2/3's 93 AKI and 1/3 87 AKI. That saves me $3 to $4 per tank, about $900 over 100k miles.