Oil Additives - Are they what they claim to be? ?

[Peter Solarik]

I already placed same questionin my previous 'thread'. It got 'burried' in other unrelated subject.
Wonder whether somebody here can put some light on the feasibility of adding the Oil Additives in engines with low milege on them.
Here in Canada (Ontario) we get some nasty winter temperatures once in a while. The question:
Is a regular oil and filter change (say - 2.500 Km) sufficient to keep the engine (37.000 km on it) in good shape, or would a change to high grade (against manufacturer reccomendation), such as Quaker State, 50/50 Synthetic, or 100% synthetic provide good enough protection?
How about the Additives, which I see on shelves in our supermarket stores in large quantities and brands?
Everyone I asked, say something else.
I remeber well the 'Slick 50' fad, how the people who sold it put it into engine, than drain it completely and run the engine again withou any apparent bad consequances. Than I hear that the Slick 50 actually (due to high temperature in engine) broke down, and destroyed the test engine (of course, the TV viewers have not seen this)..
Is here anyone, who can put some more light on it?
My Buick Century 2000, I purchased in last summer with 31.000 KM on it and would like to keep it for a while. It rides fantastic!
Cost = $ 18.000 CND.
Week after I purchased it, I seen an ad in papers by other dealer, who was offering 2.002 model for two thousand less. Needless to say, that did not make me happy!
Greetings
Peter

[tman]

I change mine every 2000 miles oil and filter. The oil I empty is cleaner than the oil some people put in! You cant tell the difference between my oil and new oil!