Waxoyl - Clear or Black?

[cadfael]

I'm about to take advantage of the half decent weather, and waxoyl under my 2-door Rangie (lovely job!).
I've nearly always used Hammerite Clear. But is there any difference in protection between Clear and Black?
Also, is it a good idea to add white spirits?
Advice much apreciated.

[TWR]

Hi, white spirit (N0 NO) regards the cleaning, steam clean your underside & make sure you do it well before applying under seal, black or clear & Hammerite the product is well known either way, the job providing the preparation is done well will pay results.