An easy answer is “yes it is a waste of $$, & time." Anything you add to you're engine oil is a waste of money that would better used to buy new oil and your most likely doing more harm then good. If you're oil needs something more or a boost of something extra - use oil that is formulated for that. In mixing additives is an exact science and you most likely will not be able to get it right by mixing yourself. The chemical reactions can be all over the place. 20 parts of A and 20 parts of part B does not always make 40 parts AB now add heat, wear metals, pressure differentials, moisture and possibly coolant or/and fuel plus the reactions of what ever your adding. Whew, I get dizzy just thinking about all the possibilities. (none of them are desired results) The best thing I think you could do is use ultra high particle filtration to improve the cleanliness of your oil. 3 part abrasion does the most damage and makes more particles and so on & so forth. Or you could just change it. Sometimes I will use a low viscosity diester oil with an offline beta3/200 filters to circulate in my engine, drain and fill with a quality motor oil. This is to clean it but that’s about it. Never run your engine with out the proper oil.