Modern Vespa

When I fuel up the HPE, I select and pay for premium, 93 Octane. But I wonder how much premium gets into the tank. I imagine the residual fuel (most likely Regular, 87 or 89 octane) in the hose and pump from the person who last used it comprises a large portion of the fuel that ends up in my tank.

What do you think?

We've been around the block a few times on this here. There have been some estimates on how much regular you might get on a shared hose, but I've concluded there isn't enough to worry about. Could be a concern when topping up, but on a nearly empty tank, nothing to lose sleep over.

You could check the pumps for premium being the last transaction.

I found 3 gas stations in my area that have separate nozzles for ethanol free 91 octane (BP and Amoco stations). Definitely not everywhere and I had to actively seek them out. I tend to frequent those stations.

According to Dr Google, hoses retain between .2 and .33 gallons. If you do the math, you're averaging about 90 octane if you fill 1.7G of 91 octane + residual 87.

OP said they get 93 octane so it would be about 92 assuming 87 was the last fuel pumped.