Car Mechanics (UK) - - Instant Expert -

‘Coolant’ in this con­text re­fers to the so­lu­tion of an­tifreeze and wa­ter that trans­fers heat around and out of the en­gine and its as­so­ci­ated an­cil­lary parts. You can buy readymixed types that you can just pour in straight from the bot­tle, but con­cen­trated fluid tends to be more cost-ef­fec­tive, es­pe­cially if you main­tain more than one ve­hi­cle. Most car man­u­fac­tur­ers rec­om­mend a 33%-50% mix of an­tifreeze and dis­tilled/deionised wa­ter, but check your hand­book and work­shop man­ual for the cor­rect con­cen­tra­tions.

While the cool­ing sys­tem ap­pears not have changed very much, the chem­istry be­hind mod­ern coolants has be­come im­mensely so­phis­ti­cated. One of the main rea­sons for the change was to in­crease drain in­ter­vals, but the down­side is that newer coolants can cor­rode cer­tain met­als that were used in older en­gines. IAT (Inor­ganic Ad­di­tive Tech­nol­ogy) is the tra­di­tional ‘uni­ver­sal’ coolant, com­mon to many pre-1995 en­gines. Typ­i­cally, these re­quire drain­ing every other year. OAT (Or­ganic Acid Tech­nol­ogy) types pos­sess longer drain in­ter­vals – typ­i­cally every five years – but are in­com­pat­i­ble with yel­low met­als, such as brass or cop­per. HOAT (Hy­brid Or­ganic Acid Tech­nol­ogy) an­tifreeze in­cor­po­rates both OAT and IAT el­e­ments for more re­cent en­gines. This aims to ad­dress scale for­ma­tion on hot spots and en­hance wa­ter pump seal life, as well tack­ling wear pro­moted by cav­i­ta­tion. Check your hand­book care­fully for the rec­om­mended coolant type. If only a car maker part num­ber is sup­plied, con­sult a cred­i­ble af­ter­mar­ket sup­plier, who should be able to iden­tify a com­pat­i­ble af­ter­mar­ket al­ter­na­tive. As cer­tain coolants are in­com­pat­i­ble with cer­tain en­gines, be ex­tremely wary of mar­ket­ing claims from com­pa­nies that their ‘uni­ver­sal’ prod­uct can be used on every ve­hi­cle.

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