Why do some cars leak oil from the rear engine seal, and others don't?

After owning several mercedes, I've realized that they have all had an oil leak. But, along came my current W124 E420 1995 with a mere 147,000 miles and there is no oil leak.

I can actually park on my concrete driveway, without leaving a stain.

Well, my question is simple. How do I keep it from developing a leak?

Special oil? No jack rabbits from red lights (me like the power of 8 cylinders)? Or what?

Thanks for the suggestions. I want to keep this gem clean and dry.

__________________
Thanks for the help
Bill Fisher

'86 560SL (186K) - Now a 'classic' : Registered as an Historic Vehicle
02 E430 in the stable
'14 LS460 (Lexus)
- - - - -
'95 E420 (198K) found a new home
'99 E320 (80K) (gave it's life for me as we hit a bumper)
'95 E420 (231K) Sold to a happy buyer, new to Mercedes
'90 300E (65K) Sold to an Mercedes Lover
'92 190E (215K) - retired to the salvage yard
'93 500SEL (214K) - Moved to another family, still runs like a young pup