Homemade thousand island dressing recipe

1 cup mayonnaise (you can use low fat if you prefer)
4 Tbsp ketchup
2 Tbsp white vinegar
4 tsp sugar
1/3 cup vegetable oil (use more to make the sauce thinner)
2 Tbsp sweet pickle relish
1 Tbsp finely minced white onion
1/4 tsp salt
Black pepper to taste