Knowing that this is one of those 'everyone has a favorite' kinds of topics, oft with strong opinions, I'll start by saying I've had good luck with Rustoleum's offerings + Waxoyl on my MG, and am leaning in that direction for the underbody and primers for the paintwork on my XJ6.

That said: I certainly am no body guy, and would like to investigate a range of options.

I open the floorboard, so to speak, and ask if anyone has a particular under-body paint, or rust inhibitor writ large, they like and would recommend for the XJ6 themselves?

 

Depends on whether you are going to do a full restoration or touch up some areas.

Important rule is get as much of the rust off as possible, cut out and weld any holes back to solid metal. Clean thorughly and dry using a heat gun.
Preperation is at least as important as the products you use to protect against rust.

Some good advice here Home - Rustbuster

I've used POR-15 but you have to be careful to read the instructions and follow them exactly. Good for areas where you cant clean rust thoroughly but not loose rust. If clean metal then Metal ready is a must.

Epoxy primers are also excellent on bare metal or where you need to put it over a rust converter.

For underseal the bilt hamber or dinitrol products are better than waxoyl IMO.
Ditto for cavity wax.

 

another option: oil-based spray undercoating, it doesn't dry, always stays "greasy" or "gooey". Just spray it wherever you need.

 

A consistent 'applicable' oil type has it's appeal: I'd be incentivized to go under every year and hit the grease certs too.

 

anybody remember Ziebart? they used to drill holes and insert a sprayer which would dispense oil-based rustproofing, it smelled like hot tar. I wonder what happened to them.

 

They still have one near our house. I had them treat an old e150 'beater' van to limp it along. I think their failing is that, over time, the tar solidifies and chips off.

 

Hi, just a thought as I will be doing something similar in the near future. A friend of mine (30 years ago) sprayed heated vaseline and his van was perfect 20 years later. (haven't seen him since)
I was thinking of using anti-seize, that nasty silver stuff cleans rust and protects and never comes off, even under heat.