Originally posted by 286 NSX:
i stay away from synthetic because local shops say it wears down your rings a lot faster. only use it if you need it, like in turbo cars, supercharged, where the temp is high. rotaries aren't allowed to even use synthetic. mazda doesn't warrenty it. same issue, it wears down the apex seals. and this is a fact.
That is actually not correct. Synthetics are significantly better lubricants than standard oils. Nothing will wear more with a synthetic. They are also significantly better at high temperatures than regualr oils, which will break down under exterme temperatures. In fact, the only applications where synthetics are not as good are those where the mechanical design relies on a certain minimum level of friction to function. For example, putting a synthetic trans oil (Redline, for ex.) in an old syncromesh transmission (old Alfa, for ex.) may cause it not to work properly because the syncros need a bit of friction to function.
There used to be a sort of 'folk lore' among mechanics that you should use regular oil to break in a motor, becuase synthetics are so slick the motor will not break in properly if you use one right from the start. This is obviously not true, and every major auto manufacturer will agree if you call and talk to a tech advisor.
The issue with Mazda rotaries is not a problem with the apex seals. It is really due to the type of oil pickup that Mazda uses in the rotary engine. Their engineers do not feel the pickup will work as well with a synthetic; hence the warning. I had a detailed discussion about this issue with a Mazda factory engineer when I was racing first gen RX-7s back in the days of dinosaurs (they won the SCCA GTU class for almost a decade straight, by the way). After consulting with them, I ran Redline in all of my rotary race motors with no problem.
I personally believe that Redline is the best synthetic, but I use Syntec in my cars because I think it is nearly as good and is more readily available. In most of the independent magazine tests of synthetic oils, Mobil One consistantly does very poorly. Even so, it is the most popular synthetic. Go figure.
Sorry to blab on so long about such a simple subject, but it is something I researched pretty heavily back when I was roadracing seriously.
[This message has been edited by David (edited 13 February 2001).]