[T3] Injector gas leak into engine oil?

[J. Jonik]

Re/ 71 Std Sqbk:     Slight smell of gas but not a wet hose to be found anywhere.  

Suspicion is that an injector may be leaking gas into engine oil.
  Hard to tell if oil at dipstick smells gassy.


Any trick to test injectors for possible leakers?

And, any way to assure that any replacement injectors (salvaged from long gone cars) are ok?    Some oldies have been kept sealed in jars...no drying out. 


 Or should we just change up to New Injectors (from our local VW shop) every five years?