Yes that's correct. HOAT is the latest incarnation and has less potential contaminants within its solution that can cause corrosion as it ages. There are three classes still available IAT, OAT and HOAT. If you mix HOAT with OAT because that''s all you have to hand you should flush the system fairly quickly and refill with OAT or HOAT. HOAT lasts longer in the vehicle, 7 years or 1000,000 miles. OAT 5 years and IAT 2 years. Never mix IAT with an OAT variant, That's the old green stuff.
HOAT was extremely expensive when it first hit the market but now generic options are available and careful shopping will get you the higher spec option for not much more than OAT.
I have never seen and original fitment rad with a broken drain plug but have heard others report it. So, just reporting on my experience. If perhaps they were replaced and over tightened to much this could be a cause. I don't know!... They are plastic, metal socket though.
Ford product should be Fomoco, however Motul do have the identical product. Not made by either company just marketed under their own brand name.
John, It won't help to drain the heater matrix out as the heater pipes enter through the heater box and are really the highest point other than the header tank. I do it the way I have explained trying not to yank at the plastic components which can only become more fragile as the years pass and having to refit a thermostat or possibly replace what was a functioning item. This leaves only clean water retained in the system with the minimum of tap water which can hold corrosive or scaling properties.
Last edited by sewin; 22/10/25 11:05 AM.
