Question:
I keep hearing conflicting requirements for oil on the RX-8. I have personally heard from ppl that Mazda Service Dept's are saying different things when it comes to oil viscosity for the Renesis Engine. One Service Dept. says to use 10w30 oil in the RX-8. They said 5w20 is not recommended for the rotary, and the manual should be changed . He said to stop using 5w-20. Another dealer used 20w-50. We all know that the manual says 5w-20 for the American version. But The European version recommeneds 10w-30 in the owners manual. What
is true with all of this?

Answer:
In regard to your inquiry, Mazda does recommend using 5W-20 engine oil for your RX-8. Mazda recommends this lighter oil for all of our vehicles because it meets the corporate average fuel economy. However, using 10W-30 engine oil will not cause any damage to the engine. Please understand, Mazda does not recommend using synthetic oil for your RX-8.

 

They're still not recommending synthetic. I thought they had a change of heart regarding synthetic oil.

 

Depending on who replies to your email, you'll hear different things. No offense, but this has been covered about 50 times, and I'm not being a smartass!

 

Here is the corporate line on why they don't "recommend" a synthetic.......Pg 1.

 

and Pg 2.

 

The above is a Mazda Australia document, obviously......and although they import and sell 5W-30, we in Australia can use a heap of other weight oils......

Gomez.

 

I do business with Mazda remanufacturing and their HEAD GUY for engine rebuilding will SCREAM AT YOU when you ask this question. Believe me, he screamed at me, and we're friends.

NO F**KING SYNTHETIC OILS!!!
They have not studied synthetics to find out which ones burn properly with oil injection for rotor seals. I have seen engines that had been run on synthetics that didn't burn, believe me, you don't want to do this to YOUR engine!

 

So the answer is.........in my case I drive in 100 degree temperatures all the time.....living in the desert southwest of the United States......I was told the RX runs hot...I was told the 5w-20w is the only oil I should use.......does anyone know if any other weight would be better in the assisting of cooling the engine.....right now if I drive in these temperatures any where from 10 minutes on (regular driving and highway) when I get to the destination, I cut the RX off and the fan runs for about 10 minutes tops.......

 

Hello,

With the heat you are talking about you should be using a 5w-30 or a 5w-40. It's a little thicker but will the hot weather it will balance itself out.

FYI--to veryify my tip run a sreach on oil and you will see the same advise.

I wish we had that type of weather here in Toronto.

 

Synthetic oils have something called "esters" that can cause seal problems. But, oils tend to evap, not burn per se - at least in piston engines. This is how one does have an oil film inside the combustion camera (i.e., because it does not burn). The rotary does run hotter though.... I think the best oils are the mineral ones from Europe. The mineral ones in US are inferior also at high temp and evap a lot - so I bet that most of the "missing" oil evaporated instead of being used in the chamber :o)

Anyway - did anyone actually try to use synthetics? I recommend Mobil 1 Full Synthetic. What material is actually the trouble seal in the new engine? I assume it is not metallic.... wonder how it holds at those temperatures in this case. Is temperature in the chamber higher than for diesel? VW diesel in Europe change oil every 15000 km (10000 miles). The new GM engines (and Mercedes - but they started to advocate Mobil 1 Synthetic after a law suit) with oil monitors indicate up to 20000 miles lifetime for gas engines. In this frame - the old 3000 change interval seems off. The 7500 by Mazda is closer to the range. Motor oils came a really long way in recent years!

Just my $0.02.

 

First info makes sense: the motor oils in Japan are closest to European standards, not US. So it make sense to import from there.

But - why is it 5W30?!? The manual for the car asks for 5W20! There is no "official" explanation there. One would be that a 5W20 with desired parameters cannot be made using highly refined base stocks (JP and EU uses increase viscosity Group II+) because it is too viscous (US uses Gr I, which are less viscous but evap more and oxidize/degrade easier).

The more strange statement is about decanting the oil. I never heard of such technique used for motor oils. All components should be soluble, if not it would block the filter! They could use filtration to fasten the process - but still, what is the solid material in there?!? I would be reticent to use such a weird quality oil, as there is no perfect decanting unless one waits years and years....

Again, my $0.02

 

Now just hoooooold the bus...........Mazda Australia import the oil from Japan in 44 gallon drums. They then "decant" it (just pour it....) into Castrol containers for resale. I'm just glad it isn't at the same mark-up as their accessories.......

And it's 5W-30 'cos we use that here....or 5W-20, or straight 40 weight, or 10W-50.....etc. Search through my recent posts, I included a pic of the oil specs page from the Australian RX-8 Owners manual.....

Gomez.

 

Nope - only the North American RX-8 manual specifies 5W20. The official Mazda requirement for everywhere outside of North America is 5W30, as specified in their owners manuals (scans have been posted many times). There was an official Mazda e-mail about this (in response to a question that one forum member sent in) that stated that 5W20 was used in NA to aid their Corporate Average Fuel Economy rating. That same e-mail stated that we could use 5W30 without any problem, including no impact to warranty.

Regards,
Gordon