I didn't know that potato salad as we know them here are mayonnaise based. I grew up eating it "German" style, which is oil and vinegar. I'm sure you can look up a recipe for it but it's mostly just boiled (or baked) potato sliced about 1/6" with onions, oil, vinegar, and salt. I forgo the onions and throw in carrots and celery but I'm sure you can vary them.

One thing I should note is it really won't taste very good with olive oil, the flavour's too strong. Best to stick to something like grapeseed or sunflower.