we called it burger sauce at the little mom & pop place I used to work at and the owner would make it by the bucketful. She used a gallon of mayo, 2 c mustard, 2 c sweet relish and 4 c ketchup. We used it on burgers & reubens, people requested it for fry dip or to dip pattymelts.

I go with 1 c mayo, 2 tbsp mustard, 2 tbsp relish and 1/4 c ketchup. Stir and chill a few hours to let flavors blend.