Here Are 15 Of The Most Closely Guarded Secrets Only Two Living People Know

10. WD-40, the garage staple has a formula so tightly guarded that it has been inside a bank vault for 50 years

WD-40 is almost used for everything – from cleaning to greasing to polishing machine parts. The formula to this popular industrial solvent is kept in a bank vault for the past 50 years and has been taken out only twice. And just like the KFC spices, the product is mixed at 3 different locations in the country and then it is passed on to the manufacturers, just so that no one gets the complete formula of the famous product.