I was asked if I wanted an engine flush for an extra £33. I asked what this was and was told they flush out all the oil... I filled my diesel Jaguar XF with petrol - do I need to have the whole fuel ...

I was asked if I wanted an engine flush for an extra £33. I asked what this was and was told they flush out all the oil... I filled my diesel Jaguar XF with petrol - do I need to have the whole fuel ...