Is the likes of g12 coolant just normal anti freeze ? Is it oil based, reason I ask is because when filling up solar panels with glycol which is antifreeze, ive always got some left and need to fill up my coolant, so could I just use this, as its its just anti freeze. Or is g12 and other anti freeze products made more engines ? This is stuff is like £1 a litre rather than the £12 /l of g12!