Possible Petrol Scam?

Just wanted to say that I'm not in anyway accusing the filling station of any misconduct and am just stating facts as witnessed by me.  

Since the insane petrol hike at the beginning of this month (post here!) I decided to change to premium 91 in order to keep my petrol costs down.  I drove up to the filling station today afternoon and asked for 'x' KD worth of premium petrol.  Now halfway through pumping, I noticed that the attendant was filling my tank with super 95 instead and called him over to point out the mistake.  He immediately stopped pumping, but demanded that I pay for the petrol that had already been pumped into my car.

Though I really shouldn't have been asked to pay for his mistake, I thought fair enough.  That is until I expressed annoyance over the error and the attendant started explaining that regardless of what octane level I chose, all three types were in fact the same price.  For example, when I ask for 4 KD worth of petrol, regardless of the type, I would still get my 4 KD worth and wouldn't have to pay any extra amount.  Huh?  Did the attendant really think I was that dumb?  A clueless impressionable woman driving up to the filling station all by her lonesome self?

It was at this point that I demanded to speak to the manager.  Now, the manager spoke very little to no English, however he seemed to understand all too quickly what had happened and told me that I didn't have to pay for the error.  This made me suspicious, and it got me thinking that this might be happening all too often.  After all, unless you were watching what type of petrol was being pumped into your car, you would be none the wiser.  You'd just pay the amount you'd asked for and be on your merry way. 

Honest mistake or perhaps intentional?  I guess I'll never know.  But it sure pays to be extra vigilant when you're at a filling station!

UPDATE:
Here's a useful fuel guide by KNPC if you're confused about what type of petrol your car needs.