Can you use high efficiency liquid detergent in old top loading washing machine?

Yes, it is safe to use HE detergent in a normal top-loader washing machine.

From Tide.com: "Our HE detergent is designed especially for HE washing machines - both front and top loading. If you have a non-HE washing machine (which is usually top-loading only), you can use HE detergentbut it's not necessary. It won't harm the machine but you'll notice less suds."