Playing it cool
QMy local motor factor has supplied antifreeze for my Rover and Imp, supposedly suitable for their Seventies aluminium engines. The label says it's OAT and contains ethylene glycol. A friend advised that OAT may be detrimental to seals and rubber parts.
Your thoughts?
Graham Scott, Rugby
Ed says
AMost coolants are based on ethylene glycol. This is the antifreezing part of the solution. In addition, there's a package of corrosion inhibitors – which is where things get confusing.
The traditional blue or green coolant that your manuals recommend has an additive package now generally known as 'silicate'. You can still buy this. Other (more recent) types are HOAT (Hybrid Organic Acid Technology) and OAT (Organic Acid Technology).
Early OAT coolants had a reputation for causing problems – but that was 40 years ago and these have been ironed out since. One caveat that remains, is that they should only be used in sealed cooling systems (i.e with an expansion tank). Older systems which have an air space in the radiator and a simple overflow tube to the ground are unsuitable, as the possible churning of air and liquid in parts of the system (especially if the water level is too low) can cause the additives to form a gel, causing blockages. Only traditional silicate coolant should be used in them. Otherwise, we think the OAT coolant you've bought will be fine. I (Ed) conducted a simple survey some years back where I asked Lada owners across the world if they'd had any problems with OAT. The Lada has a sealed system, an iron/ aluminium engine and a soldered brass radiator and heater matrix. Noone reported any issues. If you have any doubts, however, stick to what was recommended when new – silicate.