My 21 has 37000kms or roughly 22k miles. The other day I pulled the plastic covering the radiator area to have a look around. Greater than 99% of my driving is on highway. I was surprised to find that almost half of the rad surface area was covered (partially blocked) in varied vegetation and fluff for lack of a better term. No overheat issues thankfully but I could not believe how much had been ducted into the area. I was able to vacuum it easy but will be checking more regularly. With some finding overheat conditions and summer towing it takes minutes to pull the plastic tabs to have a look and clean as needed. You might be just as surprised as I was.