I Am Not So Dumb

The other day @ petrol station after pumping oil, my friends mum was there but she wanted to pump ron 97 on her car. The pump that I used only had ron 95 and diesel. Check out what happen after that :

Mum : I very worried now.
JT : Why?
Mum : I don't know if you pump diesel into the car.
JT : Where got?
Mum : Because over here is written diesel.
JT : I pump the yellow wan la.
Mum : Then what is the difference between green and yellow?
JT : Pricing?

I mean I won't be so dumb to pump diesel on my car. Both the cars at home runs on ron95. I guess when you don't reload your oil, this will happen.