I did a couple thorough dino oil changes on my cars, then switched them to synthetic. I don't trust those engine flush products and IMO they must put too much stress on the engine because they severely reduce lubrication. I just flush my engines with a quart of fresh engine oil at each oil change. This is really effective at getting out a lot of the sludge at the bottom of the oil pan.

I think the idea that synthetic oil will loosen up sludge more than dino oil is a myth. I really doubt synthetic has a greater ability to dissolve sludge. The difference is that it won't add more sludge like dino oil will.

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2004 VW Jetta TDI (manual)

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