Yep and the oil (as time goes by) that is being sent back through the intake will also settle in the intercooler, I put about 20ltr of unleaded fuel through my old 3ltr patrol intercooler once just to get the gunk out that had settled in there, and all the gunk on the intake manifold aswell,, made a big differance when it was cleaned though,,, Will be tackling the D40 after the 30000k service this time,,, Are the D40 intercoolers easy enough to take out does any one know