How to make a DIY car wash liquid

What’s a good ‘recipe’ to make car wash liquid at home?
I have used this product for a while and was happy with it. The interwebs suggest:

1/2 cup dishwashing liquid
1/2 cup baking soda
1 gallon warm water

However having never made a car wash liquid am unable to comment if this is going to be effective. What is an effective, tried and test car washing liquid recipe? I don’t want to be waxing after.