Radiator Coolant

[UK6]

Hello fellow Bristol Enthusiasts.
I write to you seeking advice on what is the best coolant to run in my old 400 motor. I have just had some minor corrosion repairs effected to my cylinder head and I would like to keep my cooling system healthy.
At present I plan on running demineralised water with perhaps a cupfull of good old soluble oil courtesy of the liquid component of "Bar's Leaks" - I won't tip in the solids.

Are there any better options out there?
I am definately not going to run glycol mixtures.

Regards,

Brett B.