We are often asked by clients whether they (or we) should use a waterless coolant. There is one supplier who appears frequently in classic car circles and who makes claims for its benefits including cooler running, lower coolant pressure, no corrosion due to no oxygen and indeed more power. Some of these claims have some truth, and some may be relevant to the Jaguar V12 and AJ6/16 engines, but we feel it necessary to put these claims into perspective, given the very high price of these coolants – typically £300 for a V12.
If these coolants were the same price as conventional coolants then we’d have no problem in recommending them, as even with marginal benefits it would make sense to maximize engine corrosion protection.
As a note, coolant is the term used to describe the mixture of water, corrosion inhibitors and anti-freeze chemicals which circulate within the engine's cooling system. Most people refer to the non-water component as 'antifreeze' but the corrosion inhibitors are just as important.
Let’s look at some of the science in these claims:
Given a system in nominal condition, then the temperature of the engine’s coolant is solely controlled by the coolant thermostat (or thermostats in the V12). All engine installations have been carefully designed by the manufacturer such that the cooling system can rid the engine of excess heat under normal operating conditions, even in hot climates. Manufacturers go to great lengths (even in 1980’s cars) to ensure reliability in both deserts and in sub-zero conditions. To avoid excessively long warm up periods in winter and overheating in summer, a thermostat is fitted which controls the flow of coolant round the engine according to its temperature. When the engine is cold the thermostat is closed, the coolant hardly circulates and so the engine heats up quickly. As the temperature rises the thermostat opens and allows the coolant to circulate to the radiator which is cooled by the fan. As the coolant cools down the thermostat closes down a bit and the process continues until the temperature reaches equilibrium at a temperature defined by the thermostat – nothing else.
To make an engine run hotter or cooler one must change the thermostat to a different temperature setting.
With this in mind, one can see that no special coolant can affect the temperature of the engine unless there is a fault in the system causing overheating beyond the capability of the system with the thermostat wide open, and even then it is not clear why waterless coolants would conduct heat away better. Overheating in road cars only occurs if the engine is producing more heat than the cooling system can dissipate. This might be due to the engine itself producing more heat than normal (virtually impossible for road cars without there being other symptoms), or the cooling system not circulating coolant well (low coolant level, failed water pump, clogged waterways) or the radiator not doing its job (radiator clogged internally or externally), or the fan being inoperative. Obviously the solution in these cases is to fix the fault, not by putting in a special coolant.
For racing cars one can expect more heat to be produced by the engine than normal, and possibly the cooling system has a smaller radiator to reduce drag and weight. In these circumstances a special coolant may help but only in ‘plastering over’ a system inadequacy or some design fault in the cylinder head allowing hot spots and local boiling to occur.
One should also bear in mind that it is not necessarily a good thing to reduce the engine’s running temperature to below the designed level. The hotter the engine the greater the temperature difference between the cooling air and the coolant, and thus the greater the rate of energy dissipation (a hot cup of coffee cools faster than a tepid one). Various other design features depend on the engine getting to heat quickly and running at the designed temperature.
Lastly, for a coolant to carry heat energy more quickly from a hot place to a cold place it must have better heat absorption qualities than water – and a range of other thermodynamic characteristics – and this claim is not made or substantiated in the waterless coolant sales literature that we’ve seen, though it may actually be the case. [As an example, many modern engine exhaust valves, which get extremely hot, often use a sodium core which, being a molten metallic element, is good at absorbing and carrying heat from the hot valve head to the shaft where it can be transmitted to the cooler valve guide and cylinder head].
The claim is made for waterless coolants that they will reduce the pressure of the coolant. We say the pressure will only be excessive if there is a fault. Here’s why:
Between the wars it was realized that the old open cooling systems of aircraft and cars limited the operating temperature inside the cylinder heads and block to 100degC – the boiling point of water. Steam is not a very good conductor of heat so the heat dissipation of a boiling water system is poor – and one loses a lot of coolant in the process. The solution was to close the system and allow the pressure to rise as the coolant temperature rose. If one increases the pressure of a liquid, its boiling point rises (and vice versa, so if one goes up high on a mountain where the atmospheric pressure is lower, water boils at lower than 100degC, so eggs won’t cook properly!). In practice, allowing the coolant to rise to 15psi (about 1bar) causes the boiling point to rise by about 30degC. So cooling systems were designed with sealing pressure caps such that the coolant could reach at least 120degC before boiling. The main effect of this was to give more ‘headroom’ for problems involving overheating the coolant so instead of boiling over (or blowing up!) the coolant could rise to 120deg at least before something had to give. This something was the pressure cap or radiator cap which is designed to release coolant or steam if the temperature rose above 120 in turn raising the pressure over 15psi. In older cars this release was a familiar sight on the roads as clouds of steam would follow an underpowered and undercooled car struggling up a hill towing a caravan! [Modern cars have fully sealed systems and any coolant expansion is taken care of by an expansion tank sealed from the atmosphere].
Again, for post-war cars this would only happen if there was a fault, and this is what needs fixing – not a coolant type change. So in summary, cars are designed to cope with higher than boiling point coolant temperature. The extra headroom allegedly given by waterless coolants is unnecessary in road cars.
It is true that fresh water contains oxygen and pure waterless coolants do not. And it is true that oxygen in the coolant can promote corrosion in iron or steel cooling system components. But conventional water-based coolants lose their oxygen in the first few hot-cold-hot cycles – like a fizzy drink going flat – and no further corrosion can take place. If one needs to keep topping up the system with fresh water because of a leak, then this fresh water will cause corrosion and scaling faster – but all one needs to do is fix the leak.
Corrosion in engines is a bad thing for a number of reasons, so anything that stops this is good. But conventional glycol or OAT coolant additives (“antifreeze”) do just as good a job for a fraction of the price. This problem is largely confined to iron block (or cylinder head) engines. Alloy engines such as the Jaguar V12, AJ6/16 engines do not suffer from serious internal corrosion, though to be fair, the iron-bladed water pump does.
Glycol coolants (up until recently the most common type) have a life of around 2 years before the corrosion-inhibitors lose their efficacy. We use long-life OAT coolant (coloured red) which lasts a good 5 years. Waterless coolants claim to last forever and if so this is a good thing as many owners do not change their coolant at the right intervals, or ensure that their garage does. However, if one loses the coolant due to a leak, burst hose, or because of maintenance (e.g. changing the water pump), one has lost £300 of waterless coolant.
Oh dear! This claim is unfounded in normal road engines unless there is some fault. The power of an engine is primarily related to its capacity and its compression ratio. There are more subtle effects from ignition timing, pumping efficiency (i.e. inlet and exhaust design), inlet air temperature and pressure and so on. Coolant type will have negligible effect. In old, badly designed blocks and cylinder heads there may be poor internal flow of the coolant, allowing local pockets of steam to occur which would occur less readily with waterless coolants, but modern engines including 1980’s Jaguar engines do not suffer from this effect. However for vintage engines it could well be a problem in which case waterless coolants have a place.
Remember that a lot of highly efficient and powerful engines are actually air-cooled (many a Porsche 911 for example) so coolant is definitely not an issue!
If your engine is overheating it needs to be fixed. If your engine is boiling over, ditto. You won’t get more power from a fault-free road engine by changing the coolant (if it did we’d be seeing dynamometer graphs proving it…). If it was the same cost as conventional coolants I’d say go for it – the longer corrosion resistance life is a real benefit, but at 10 – 15 times the price I’d say ‘why bother’?