A fabulous start in the cleaning of my engine block coolant galleries. After looking at dozens of products with no solid results/proof that the product/method is superior, I went the cheap route ($20) of using White Vinegar (5% acidic). vs $200 of CLR, Evaporust, etc..etc.. A good soak and a little gentle brush scrubbing, the results are more than acceptable for my application. I will scrub more and soak a second time, but this is a good start on my classic mini engine block.. Lone Star Mini