"
OAT" stands for something which I can't remember! The technical term is
G11 and is
usually pink in colour (as per your pic). Supposed to last 10 years before needing replacement (though who is comfortable with the idea of 10 year old fluid in their car? not me...) OAT uses relatively modern chemically engineered additives. As a GENERAL (and I can't stress that enough)
2001 onwards cars use OAT. Introduced as it works very well with aluminium engine blocks.
"
IAT" also stands for something which I can't remember
Technical term is
G10,
usually blue. Lasts 2 to 3 years before needing replacement. Is made predominantly from naturally occuring/easily obtainable silicone_something. As an equally GENERAL rule of thumb, IAT/G10/blue is used for
pre-2001 cars.
You have to get the correct one. You absolutely 100% can not mix the two types. In theory, though Daniel had a bad experience, it should be perfectly fine to mix two different brands of the same type (i.e. Halfords OAT/G11/pink & something else OAT/G11/pink)
As getting the correct type is so crucial,
it will almost certainly say in the vehicle handbook (no longer have a 182 so can't look, sorry!)
which type you need. Go with whatever that says tbh!
Completely irrelavent to us Renault folk but maybe of interest none-the-less, VAG have gone off & decided there is a need to invent G11+, G11++ and G12 which have yet more rules about what you can and can't mix. This stuff is generally only available from VAG and apparantly VAG will come to your house and assassinate you if you put standard G11 and not their special +/++/12 stuff in your engine. More not-actually-relavent-to-your-Q-but-coolant-related-info is that you can generally use OAT/G11/pink in older engines that originally took IAT/G10/blue if you drain & flush the entire system and start from scratch - though why you wouldn't use the correct type is beyond me.