I got an old clunker I drive to work in everyday, and leaks and burns about 1/4-1/2 quart a week and I just keep dumping havoline in. I found chevron supreme at a doller store for $2 a quart and I am paying $2.76 a quart for havoline, first is chevron supreme any good? and will it hurt to just start mixing it in with the havoline? I do 6k oci on the truck changing the filter at every 3k