[g259fsg]

What do folk think about using OAT coolant in our cars, particularly the older ones like my 1990 214 GSi? I've read somewhere that it's not the best for classic cars and it's better to stick to the old-fashioned blue stuff.

Cheers,
Hugh

[Johnny 216GSi]

Better to stick with the old stuff - standard blue mono-ethylene glycol.

OAT doesn't mix with the old stuff so you have to properly flush your system, possibly also refilling with a sacrificial OAT coolant mix run in the car for a few miles, then drained and refilled with OAT again to be sure there's no old glycol in the mix in your engine.

OAT *may* effect seals and the like on cars that were in production before OAT had been developed.

Having said that, I've seen at least one 1994 R8 running on OAT and it didn't have coolant system problems.

I've personally considered another route - Prestone "Yellow" universal anti-freeze, as they claim it's 100% compatible with all engines and will freely mix with residual old coolant of any type and cause no problems at all. Plus it has an anti-corrosion service life of 10 years!! There's no prep involved like with fancy waterless coolants - just drain and refill with Prestone.

I may still go this route but I haven't yet. I really like the 10-year anti-corrosion guarantee, the fact it's Prestone, that it's 100% compatible with no preparation required and that it's an OEM product/part used by some vehicle manufacturers.

[g259fsg]

I was thinking mainly of the hoses as some of mine are quite old/original. When the local garage did the headgasket earlier this month they refilled with stuff that has a reddish brown colour and it smells different too. I'll need to check with them what they have used. I would probably prefer to use the blue stuff. But maybe there is nothing to worry about.

[crepello]

It wasn't from a definitive source, but I've seen it written that OAT eats copper alloys,
such as brass. The heater matrix of the earlier R8s certainly looks brassy.

[g259fsg]

This guide seems to confirm some metals are not protected by OAT so best to avoid it in older vehicles https://www.valvoline.com/en-eur/all-yo ... -coolants/

[itcaptainslow]

I’ve filled my 1995 R8 with OAT after doing the head gasket a couple of years ago. The system was flushed fully (and the engine stripped down to the block, liners, pistons & crank) so no trace of the old coolant was left.

Doesn’t seem to have any ill effect. Filled my old BRM with OAT too using the same principle-again no issue. A thorough flush seems to be the key.

[JOHNDQ]

OAT coolant attacks yellow metals so if you got a early heater matrix or radiator you might have problems wouldn't use it in pre 95 cars

[Johnny 216GSi]

I've just been dealing with minor corrosion at the front of my car. I was looking at corrosion of the top and bottom frames of he radiator and then just scratched through the metal end caps of the matrix where they're formed onto the plastic frame tanks left and right, and they're gold-coloured metal so I'm assuming brass. I've always stuck with mono-ethylene glycol so I'm not in trouble, but I'm definitely considering Prestone Yellow Universal in the future.

[g259fsg]

Have checked back with the garage about what they put in the 214 after the head gasket job. It's a reddish brown colour and smells quite strongly of organic chemicals. This is the stuff, Cooltec Ultra-long Life Coolant.
https://www.arnoldclarkautoparts.com/pr ... eeze-5ltrs .

Not sure I'm too happy using this stuff over the long term. Apart from the heater matrix possibly using copper/brass, I know for certain that the two temperature sensors and the radiator fan switch are all brass components. The radiator is made by Valeo, and looks like a stainless steel core, so probably no problem with that.

Thinking I may well flush this out and replace with Prestone or regular blue coolant.

Does anyone have any further comments?

[crepello]

I have a NOS Valeo R8 heater matrix among my spares - it's very brassy looking. I replaced
my failed copper radiator with a newer technology Valeo one. I'd say that's an aluminium
alloy core, like yours, and probably basically the same as in the later OAT-compatible cars.