I have a 2004 Nissan Altima with 105,000 miles and a Nissan Pathfinder with 88,000. I just started doing maintenance myself and changed the oil, putting sythetic in both cars for the first time. They’re running fine but I’ve been reading alot about not starting to use sythetic in cars with this many miles and about how synthetic can find leaks and cracks in engines more. Should I just go back to a conventional or maybe a blend? Please help!!!
These claims, if they ever were true, are not true now. If you’re using the correct weight oil as specified in your manual, you should have no problems.
Run the synthetic oil, but monitor if oil leaks begin to occur. If they do, then come back, and I’ll explain why.
Tester, I Can’t Wait To See If Leaks Begin! Tell Me Now, Please!
Does it have anything to do with cleaning / anti-sludging propertiies or molecule sizes?
The molecules of synthetic oil are all UNIFORM in size, unlike mineral oil, where they have a variety of shapes and sizes. They are not smaller in size!
As a result, for any given weight, synthetic has much better lubricating qualities (lubricity) and the oil flows much better as well. I believe there is some truth to the rumor that synthetic oil can “find” smaller openings (leak points) than mineral oil, because it flows better.
There is no truth to the rumor, however, that synthetics have better detergents that flush out “false seals”. This quality is true if you change transmission fluid that has been left in too long. The plugged up holes (leaks)will,be opened up by the new fluid, and you may have some leaks. Again transmission FAILURE after fluid changes cannot be blamed on the new fluid. The transmission was failing already in this case.
In your case nothing bad will happen, unless your vehicles were poorly maintained to start with; I would just select the right viscosity as pointed out by others. My Nissan with 125,000 miles uses Mobil 1 without any leaks or oil consumption.