This product is a high viscosity low friction mineral oil which has been specifically formulated for worm and other types of steering box.
Tested by Rolls-Royce and Bentley engineers who have reported outstanding transformation in steering characteristics.
https://www.millersoils.co.uk/wp-content/uploads/2019/11/Vintage-Worm-Steering-Box-Oil.pdf
https://www.millersoils.co.uk/wp-content/uploads/2019/12/7921-1.pdf