Had 2 gen 6 gt4s 1st one I did 21k in the year I had it,the car was 13 yrs old then,4 x oil changes,4 x sets plugs,both front s/s bottom arms & fig 8s,the s/s was due for changing anyway,was what it cost me,seems your gt4 was unlucky having the c/cooler go, my gt4 I have now the clutch popped within 500mls what the heck,if you want a faff you dont worry about fuel economy its a fooking performance car,you dont buy a M3,Porsche,Audi RS,or the likes on mpg,people are forever asking for running cost,s from gt4 owners,do your homework when buying get a nice one it will treat you well amd always put a smile on your face,how many 10-15 year old cars can still do that today & still blow the majority of new stuff into the weeds in standard form ?? Bite the bullet get a faff