What would happen if i put synthetic oil in my old car?

well its not that old.. its a nissan altima 98


its been using regular engine oil for a long time. what would happen if i use synthetic oil? someone told me that it will damage some plastics and cause leaks, then its gonna clean the sludge in the engine and the oil will be dirty in a couple km....





should i continue using regular engine oil or should i switch?What would happen if i put synthetic oil in my old car?
i disagree with your answers








if your putting synthetic in a older motor your going to be having a faster flow rate.








if you want to properly do this.





for your next oil change ie ((uses 5 quarts, use 4 quarts conventional and 1 SYNTHETIC, then next oil change use 3 quarts conventional then 2 SYNTHETIC, and so on,





this is the proper method AND STAY AWAY FROM ANY SORT OF FLUSHES%26lt; ENGINES FLUSHES%26lt;TRANS FLUSHES, it removes :Particles that helps sealing to be properWhat would happen if i put synthetic oil in my old car?
if you been changing your oil every 3k, and you don't have any oil leak. you don't have anything to worry about. changing to synthetic will not fix anything that's already wrong but won't make anything go bad either.
It may well clean up the old engine...if sludge is keeping the oil from leaking at some of the gaskets you could experience some oil leaks...but you should get better mileage and the engine should run cooler.
you can safely switch to synthetic oil in your application