Ford ranger

I bought a ford ranger in 2020 August at Basil green Ford. It hasn't reached 36000km. It then started smoking and powerless and never started again. I called the dealer to tell them about the problem and they told me to bring the car. I did that with my own money. The car was? "fixed" and I collected it on the 13th of March 2023. I drove less than 150km after collection. On the 15th March 2023, it gave me the same problem and I got stuck in the middle of the road. I called the AA and they took the car to Casey Ford as it was the nearest Ford dealership. I then received a call from the service Manager telling me that the diesel is contaminated and I have to pay +-R30 000 for it to be fixed because the warranty can not pay for it. My question and confusion is : How can the diesel be contaminated meanwhile it is the same diesel it had when it went to Basil green Ford, I never added any because it was full tank when it went. I was also amazed when the manager told me that the diesel is contaminated before it was even tested. Another confusion is that how is that my fault because I buy it from a registered garage. How can warranty not pay meanwhile it is still under warranty?

Ford cannot be trusted because they are not reliable and they don't care about their customers.