Panacea? Plasticizer!

The cause for a smaller or larger oil leakage is - if nothing is broken, loose or torn - practically always the same.

It is almost always a sealing ring (oil seal, Simmer ring, invented in 1939) that becomes incontinent. Such a component that only costs a handful of change, however, usually requires a lot of time and effort in replacement. Great minds quickly searched for faster ways to solve that kind of problem.

The idea of ​​repairing the case simply by adding an additive to the oil is, of course, extremely attractive.

This miracle addition has been found, but only works on 'modern', elastomeric oil sealing rings. Not on felted seals, graphite asbestos cords and similar solutions dating back to the steam era. 

The reason why oil seals give up the ghost is clear: elastomeric seals, so named after the type of plastic that make them up to a large extent, become brittle over time. the elastomers contain plasticizers, which partly “volatilize” due to continuous contact with oil, but mainly due to thermal loads.

Elastomeric seals sounds fancy, that designation simply covers most oil seals, O-rings, and valve stem seals. Those valve stem seals were the explanation of the famous 'blue cloud' in tired BMW car blocks of the past ...

DropStop, Lec Wec and other sealants contain the plasticizer Di-N-Butyl-Maleinate, which makes the elastomeric plastics on contact, like human skin does with Nivea. Like human skin Di-N-butylzinn-di(monomethyl) -maleate is less. The sealing lips that have been treated in this way swell a little, but mainly get their elasticity back and can perform their task perfectly again. "While it lasts".

The fact that various providers call it 'softening and swelling' is simply because that sounds better.

So much for the theory. We have treated a well-lived BMW R69S combination, with significant oil losses to the rear crankshaft oil seal with a dose of Lec-Wec. In accordance with the manufacturer's specifications, we added exactly 3 percent of the additive to the engine oil. In fact, the problem disappeared completely after a few days (after about 500 kilometers).

Our conclusion: If the sealing lips have a mechanical damage, a crack or something, then only a new oil seal can solve the problem. And with damaged - run-in sealing surfaces or run-in shafts, DropStop, Lec-Wec or similar means will at best mask the problem, but not fix it permanently.

Important note from the providers: use a correct dosage of the additive. "More" is not always better. Fortunately, the stuff is so heavily priced that the price has a stimulating effect on the right dosage.

But the additives are in any case cheaper than the dismantling of an engine, a gearbox or an axle and for that reason alone worth a try - as long as it concerns a leaky seal.

For the BMW in question, the 'repair' has worked for at least two more seasons. After that it was just time to get the whole block going.