The flat 4 continues to amaze me.
At 80 mph any GM small block is running at 1900 rpm with a  700 R-4
trans.
The VW at 80 is running at or around 4600 rpm.
This is mind boggling.
 It is a flat opposed engine though and evenly balanced in the way they
run.
Figure for a longevity factor I would think that 4 grand or maybe even
4200 would be safe to run all day long without overstressing the engine.
And your looking at about 70 to 73 mph.
That's pretty much where I max the engine out for cruising, and seems to
have not caused any long term damage.
Not for 98,234 miles worth anyway.

RC