Engine coolant slightly low when cold - problem?
The different OAT coolants have varying chemistries to specifications set by the manufacturers of the cars.
OAT coolants can cause damage to some materials in your cooling system, specifically natural rubber seals. OAT coolants also lack the initial surface coating capabilities of older Glycol based chemistries. The benefits of the OAT range are in the long service life they offer as the chemicals in the coolants don't degrade as quickly.
The downside is that they offer less protection against cavitation in low pressure environments, and can eat seals.
Aftermarket OAT products cover themselves by specifying ages of car that they can't be fitted to.
If your car needs topping up, it is best to use the same brand and specification of coolant, however, if that isn't feasible, OAT mixes with OAT, and Glycol mixes with Glycol.
OAT and Glycol DO NOT mix.
If you need coolant to top up, stick to a known, large brand as they will have done the chemistry to avoid lawsuits. Read the bottle and check your car is in the age range.
I use Comma Super long life red
Because it is a:
5 Years Longlife Protection.
Protects against freezing and overheating.
Ethylene glycol based concentrate.
Silicate free with Organic Acid Technology.
The product recommended for the car is X30 which is a similar product, but more expensive:
Ethylene glycol based antifreeze & coolant with OAT (Organic Additive Technology) inhibitors. Protects against corrosion, overheating and freezing. Typical service life of up to 5 years. Safeguarded with bittering agent to help prevent accidental ingestion.
Each to their own.
The Comma superlonglife red is £16.99 for 5 litre of concentrate and the X30 is £25.99 for 5 litres.