Mazda: RX8 engine oil, product contamination, range of tolerance

Question
Hi, my girlfriend has a 2007 RX8. We have been getting conflicting reports about which type of engine oil to use. Synthetic or conventional and which viscosity. Also we've been told the engine oil doesn't ever need changing as it uses oil so it gets topped up enough. Just change the filter regularly is adequate. Is this true and wouldn't it be a waste of time to use synthetic if it is being topped up so regulary?
We're interested in your thoughts.
Thanks
Phil

Answer
5w-20 is the standard viscosity.  In hotter climates and extreme summers a 5w-30 is acceptable.  We recommend use of conventional oil in the Rotary.  We use Valvoline as a standard.  If you keep up with your services and add as needed then conventional is the better choice fir the application.  With piston engines we certainly recommend full synthetic.

The topic has been widely debated.  Synthetic oils flat out perform better than conventional.  In the past some Rotary engine failures were blamed on synthetic oil which is unfounded in fact just speculation.  In reality synthetic oils do the same job as conventional just with a broader range of tolerance to heat, wear and break down.  Fuel and by-product contamination affects all oils.  Lack of proper attention will cause issues with any engine.

Rotary engines do consume oil as part of the secondary metering system . Conventional oils are better in this type system.  Weekly checks of the fluid levels are common with use.  In no way does this mean you don't have to change the oil it does however, mean you can extend the duration of change intervals.  It is not recommended to exceed 5,000 miles between services and filter changing.  We use Mazda or K&N filters.

Let the dip stick be your guide.  Some people can't tolerate when their oil discolors.  Some could care less.  As oil breaks down, becomes heat stressed and fuel contaminated it changes colors usually dark browns to black.  One key to longevity, don't let it get to that point and you'll be fine.  Since no two cars see the same use and different climates and geography bring different wear there is no base line standard advice beyond that to give you.

service@miatashop.com