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Old 04-26-2008, 04:21 PM
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babymog babymog is offline
Loose Cannon - No Balls
 
Join Date: Jan 2006
Location: Northeast Indiana
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There is no difference to seals between synthetic and dino oils.

There are advantages to the synthetic oils, some feel it's worth the extra expense, some don't. I run it in all gearboxes, hydraulics, and engines, I like the stuff and have been running it almost exclusively for 30years. Never had a leak increase or start as a result of synthetic oil use.

If it leaks on syn oil, Mercedes' official stance was (might still be) that you have a leak, and syn oil will likely get through it in larger quantities as it doesn't thicken to molassis levels when cold and stop leaking the way that dino oil does.

The myth started back in the 70s, when the original formulations of synthetic oils didn't contain enough compounds to swell the seals equivalent to dino oils. Old seals without the elasticity to make up the difference would be prone to leakage when switched to syn oil. Same problem that we now have with ULSD and o-rings in injection systems.

Later formulations of syn oils (late '70s - early '80s) had the additive packages tuned/tweaked to emulate dino oils with similar seal swell rates, so this myth is out-of-date by about a quarter-century. Still, people like to be against anything just to have an opinion, so detractors of anything are easy to find.

Buy and run the oils you want. If it leaks with syn oil, switching back to dino oil will restore the leak/seal to what it was before switching according to Mercedes-Benz The Star article ~ 2002.
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