My first inline motor,  a 1.8l from a cabriolet, had no oil/coolant heat
exchanger.  When I changed it to an ABA 2.0 liter block, I ran it for a
while without that cooler, reading the part was "weak" and prone to fail..
   But my oil temperature was going higher than I wanted, so I installed
the stock cooler, opting to not believe that it won't fail, like many
others seem to do. And...it was easy and I had one.  It did the job,
bringing my normal oil temperature down by about 15 Degrees, F.
  Mine failed, and it makes a big mess, just for starters.. I was amazed,
going on you tube, at the sheer number of videos dealing with oil in the VW
coolant from failed stock coolers... Wish I'd looked at U-tube before I'd
put that peice into my van...
   The floor of my shop has a nice slick oil-shine right now... kerosene
mopping tomorrow.
  Ugly mess, but it could much worse..