Check Engine Light comes on when Low Octane Fuel Added?

Hi -

Recently bought a 2001.5 Passat 1.8 Turbo.

We were not originally aware that the engine required high octane fuel, and the check engine light came on immediately after fueling the vehicle.

Once we began using high octane fuel, the light stopped coming on.

My wife filled the tank the other day, and the light came on immediately, despite the fact she filled up with 92 octane (she thinks).

Is it possible that the light is coming on due to fuel type? I've never heard of this before, but this is our first VW, and first turbo. If it is possible, I presume that perhaps the gas station was knowingly or unknowingly selling low octane fuel out of the premium tank.

Any thoughts? Thanks in advance for any assistance you can provide.

I really don't think it's octane related. Are you cramming every drop of fuel you can into the tank or stopping the first time the pump clicks off? You can have the codes read for free at most Autozone or Advanced Auto stores.

1.8t have problems with "random misfires" than can be associated with low octane fuel. It even says in the owners manual "use 92+ octane."