Synthetic Oil good or bad?

[oasis]

The difficulty with this subject is there is little genuine scientific testing between the two. Most of the testing I've read at different sites deals with temperatures under stress, and there is little mention on the methodology used.

In other words, even is some of these "test cases," it is difficult to know if proper scientific methods were observed.

There is a lot of opinion and anecdotal evidence out "there." To make matters more confusing, the range of conclusions go from synthetic oil is always better to changing your oil and filter is more important than any oil choice to choosing the proper viscosity is more important.

There are three 2002 VW's in our family -- each with a different engine. The owner's manual says synthetic oil for the TDI, and conventional oil for the 2.0 and the 1.8T. The dealer now says they will only use synthetic oil for all engines because of sludging problems. Our long-time shop specializing in VW's says this is bogus for the 2.0 as it hasn't been prone to sludging but not a bad idea for the 1.8T.

There you have it ... three different opinions all dealing with 2002 models.

The most prevailing opinion I have read and/or heard is do not switch to synthetic oil if your engine has X miles on it. I have seen this with the additional caveat of unless the engine had had a top- and bottom-end rebuild. (The X number of miles ranges from 50,000 to 100,000 depending on who is voicing the opinion.)

I have neither seen nor heard anyone who recommends synthetic oil for a Type I engine. Whether this is because Type I's tend to leak more or is made of magnesium or both or something else, I don't know. And as I said, what I have read has not been shown to being scientific anyway.

It would be interesting for Jake Raby to pipe in his opinion here. He may have some scientific information and even if he doesn't, I'm sure his anecdotal evidence would prove informative at the very least.

The only thing I know is synthetic oil is slicker to the feel.