Today's synthetics are tested to make sure they don't damage seals so unless your seals are really worn out I wouldn't worry at all about switching to a synthetic. Synthetic oils are vastly superior to their petroleum counterparts. They have more consistent viscosity, they flow better in the cold, they hold up better under heat and pressure, they don't deposit sludge, they have better detergency, and they don't evaporate as much. The only disadvantage is they cost more, but as with most things you get what you pay for. Beware of fake synthetics like Castrol and a few others who advertise Group 3 hydrocracked oils as synthetic. As far as I know the only real synthetics are Mobil1, Amsoil and Redline.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

So many peoples do not know many things & talking very loud.
So many articles about Oils - or go to Yahoo - Google & look read.
Synthetic Oils are best - if your engine cannot hold mean you run down & need rebuild. Save on Oil pay for repairs.
Up to all who want on own believes what is best.
Amsoil is # 1 & no body can tell - I used on my cars.
190D - 900 000 km original engine.

Totally different products.

http://www.bobistheoilguy.com/moly1.html