Ok, might be a stupid question, but does it hurt anything if I mix both regular 87 octane and premium 93 octane?

My truck runs on 93, so when I get gas for that I will typically take gas cans and fill up the HHR with those since I get a Kroger Fuel discount. Since I currently have 3/4 tank of 87 octane, will it hurt to top it off with 93?

no mixing higher octane to a lower is not a problem

Cool...thanks! I didn't think it would hurt anything, but I just wanted to be sure.

Ok, might be a stupid question, but does it hurt anything if I mix both regular 87 octane and premium 93 octane?

This is how to get mid-grade gas. The gas stations do it for you when you purchase the mid-grade gas.

So on another note, how is it that there are 3 different grades of gas at a station, if they only have one tank underground? How is it that one truck full of gas can be separate grades in the same truck, which all go down to the same tank, and come out of the same pump?

First, stations don't have one tank. Depending on the type of station they either have 2 tanks and blend the gas at the pump or they have 3 tanks and just stock 3 different octanes. Take a look sometime and you will see metal covers in the ground where the tanks are and they will be painted different colors to indicate what tank is which fuel.

As for the tanker truck, it doesn't have 1 tank in it. It has multiple tanks with multiple blends.

Ah, ok. Wouldn't have guessed there is more than one in the truck though. I've always wondered that...

Look at one sometime and you can see multiple valves on the outside for them to drain from. Sometimes the driver will actually connect multiple hoses at the same time depending on how the truck is rigged.