P38 Monkey

Well-Known Member
1997 P38 4.0SE
I thought I understood the various types of coolant...
Blue/green IAT for older cars (mine currently has this colour) - change every 2-3 years.
Red/pink OAT for newer cars. Never to be mixed with IAT. Lasts indefinitely.
HOAT (yellow?) - not sure about this one but never used it.
My P38 was imported from Japan about 3 years ago so probably could do with a coolant change.
Opie Oils list IAT diluted ready-to-use for my P38 in 1L and 5L bottles. So far so good.
Then I read the P38 user handbook.
It says IAT with OAT additives is best. WHAT?!!
It also says "DO NOT top-up or refill with conventional anti-freeze formulations". WHAT?!!
Searching this forum, it seems most people use blue/green IAT and some people switch to pink OAT after major engine rebuilds etc.
Help please....!
 
The blue green stuff was all that was available when the engine was designed. The more modern OAT came in later and it's what land rover choose because of the service interval. It still needs changing but reckoned to last up to 10 years, i think. I use the green, but i think both are ok
 
The blue green stuff was all that was available when the engine was designed. The more modern OAT came in later and it's what land rover choose because of the service interval. It still needs changing but reckoned to last up to 10 years, i think. I use the green, but i think both are ok
Yes, that is as I understand it, with the proviso that people say you can't mix IAT and OAT as it apparently forms a gel and blocks the radiator.
The P38 handbook refers to Havoline XLC which is OAT so I guess that is the one to use, mixed 50/50.
I'll switch to XLC with a good flushing out at some stage.
Might fit a new thermostat at the same time to make the flushing easier.
 
1997 P38 4.0SE
I thought I understood the various types of coolant...
Blue/green IAT for older cars (mine currently has this colour) - change every 2-3 years.
Red/pink OAT for newer cars. Never to be mixed with IAT. Lasts indefinitely.
HOAT (yellow?) - not sure about this one but never used it.
My P38 was imported from Japan about 3 years ago so probably could do with a coolant change.
Opie Oils list IAT diluted ready-to-use for my P38 in 1L and 5L bottles. So far so good.
Then I read the P38 user handbook.
It says IAT with OAT additives is best. WHAT?!!
It also says "DO NOT top-up or refill with conventional anti-freeze formulations". WHAT?!!
Searching this forum, it seems most people use blue/green IAT and some people switch to pink OAT after major engine rebuilds etc.
Help please....!
Use the orange/red one in my doozle. Thats what local indy recommended when he changed my engine 6 years ago
 
Use the orange/red one in my doozle. Thats what local indy recommended when he changed my engine 6 years ago
Thanks for that - looks like my P38 has IAT when it is best to have OAT. I'll drain, flush and refill with Havoline XLC OAT.
As ever, actual experience of people in this forum is invaluable.
 
1997 P38 4.0SE
I thought I understood the various types of coolant...
Blue/green IAT for older cars (mine currently has this colour) - change every 2-3 years.
Red/pink OAT for newer cars. Never to be mixed with IAT. Lasts indefinitely.
HOAT (yellow?) - not sure about this one but never used it.
My P38 was imported from Japan about 3 years ago so probably could do with a coolant change.
Opie Oils list IAT diluted ready-to-use for my P38 in 1L and 5L bottles. So far so good.
Then I read the P38 user handbook.
It says IAT with OAT additives is best. WHAT?!!
It also says "DO NOT top-up or refill with conventional anti-freeze formulations". WHAT?!!
Searching this forum, it seems most people use blue/green IAT and some people switch to pink OAT after major engine rebuilds etc.
Help please....!

Colours aren't consistent so make sure you read the ingredients.
 
From I've seen and dealt with yellow/green is popular with renault and older Citroëns. Pink is popular with vw group and modern Citroën and peugeot. Mercs like the blue type.. Toyota typically orange. :)
 
Otto was on pink coolant when we got him, having not long had a rad and waterpump apparently. So that is what we've stuck with and he seems fine. 4.0 GEMS V8.
 

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