Just want to share. I unfortunately filed up my Polo with unleaded fuel instead of diesel!

Luckily I've noticed it before starting up and after towing etc. got it drained and they reasured me there will be no damage. Let's hope! Back at the filling station the manager showed me a New 'Dieselsmartcap' that are on the market. It replaces my current Diesel cap. Its orange and purple in colour and some sort of gimic prevents me from opening it by hand. The only way to open this cap is to take the DIESEL nozzle, put it into the cap and release it with a turn of your wrist. The diesel nozzle is already in your hand and you can just go ahead and fill up.

I got more info on their website: Dieselsmartcap.com

Wish I had it earlier!