they told me it's all wrong and I don't need to change the oil every 6k miles
Tell them to go back to eLearn and print out whatever mystical document they've read that says you don't need 6k oil changes. They won't be able to, of course.
You could, if you like, print out a copy of page 17 of AGP esseesse supplement I've attached below, which clearly states 10,000km (6,000 mile) oil and filter changes.
Your Privacy Choices