Oil Blends

For years, I’ve only used conventional oil in my cars and have changed 2500-3000 miles. Now I’ve used 1 qt of synthetic and the remainder as conventional making my own blend. Does anyone know what percent synthetic is in say valvoline durablend or castrol syntec blend??? I’ve heard maybe 10% on this board years ago but does any really know/work for these companies to say how much synthetic is contained in the blends?? if it’s 10%, it would be better to buy 3-4 qts of conventional and one full synthetic and mix them yourself. Thanks in advance. Sorry to beat a dead horse again (another oil question).

Everything you ever wanted to know about oil, and more.

IMO, synthetic blend oils are only as good as the inferior ingredient. The regular oil. This is the same as adding a pint of Johnnie Walker gold label whiskey to a bottle of Canadian Club whiskey. The Johnnie Walker isn’t going to make the Canadian Club taste any better.


Yes, not worth the trouble, especially if you’re changing every 3k. I can imagine no benefit.