Underseal or Waxoil?

[NigelA]

If there are crevices where there is rust I generally spray WD40 first on the basis that being very thin by comparison with Waxoil it will probably go further by capillary action. I then follow it, quite quickly, with Waxoil in the hope that the presence of the WD40 will help the Waxoil go further into the crevice/s.

Underbody I mostly favour black Waxoil except where it is going to be beaten-up by what is thrown back by the front tyres, then I prefer the Hammerite. But does the Hammerite underseal have equally good anti-rust properties?

Thanks in advance for any helpful comments.

[Brianmoooore]

Never, ever put bitumen based cr*p on an E30. It makes future painting impossible, and after s few years will harden, begin to lift, trap water, and quickly turn the underside into orange powder. This stuff is intended for bridge dodging Transit vans and similar.
E30 underseal should be polyurethane based, and its not cheap.
Waxoil is used in cavities and other hidden places, and can be encouraged to flow right in by the careful use of a heat gun.

[NigelA]

Many thanks, Brian. Prompt and helpful as usual. Much appreciated.

So are you also saying, if you don't want to use a heat gun, not to use WD40 to assist Waxoil into the cavities?

[Brianmoooore]

White spirit would be a cheaper alternative to thin waxoyl, but the trouble with that is that it won't only just run in, but will run out again, leaving a very thin film. A heat gun will get the waxoyl as thin as water, but then, with the heat removed, it's back to a thick wax again in seconds, and stays put while the solvent evaporates.

[NigelA]

Thanks, Brian. So sensible, when you think about it.

[sprocketman]

I would suggest Dinatrol Hard Wax for the undersides of vehicles,apply either waxoyl or Dinatrol cavity wax first (for rustproofing purposes) then the hard wax over the top.
It dries to leave a lovely finish and is not like underseal/shutz where it will dry out completely and allow water underneath!!

[pnd]

mix waxoyl with old engine oil to thin it.

[NigelA]

Many thanks, sproketman and pnd for your helpful contributions.

[RobWill116]

If you don't want to use a heat gun, heat up your waxoyl by placing it in a tub with boiling water for 15mins. And do the same with your schutz gun to make sure it doesn't go thick as soon as its sprayed through. Always works for me