In the US according to the manual 🤔 we are supposed to use 5w20. Unless you regard the manual as the Bible, which some do as I have come to find out, most of us don't. Generally it is 5w30 or 10w40. I have been using 5w30 as my preference.

However recently I watched a video where a rotary builder (Essex Rotary in the UK) claims that using a lighter than 10w40 does not lubricate certain parts of the engine properly.

Before jumping into 10w40, I thought I would mix 10w30 and 10w40 50/50 giving me 10w35. I can hear some of you laughing already 🤪. 2 reasons....for some reason Castrol GTX is $10 more for 40 than 30. Yes I know....cheapskate....but I'm retired on ss and it ain't much, believe me. And I just figured I would transition into a heavier oil for the next couple of oil changes.....yea, yea.....dumb idea. After all, oil is oil.

Now that some of you are slapping your forehead with the palm of your hand, you have to admit....I keep things entertaining around here. 😁
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Find the courage to use 20w50 and you'll never have to ask anyone about oil again.

 

I've seen it but to be honest it scares me a little. Not the 20 because I take my car off the road for the winter. I haven't heard of too many that use it. Would love to hear from those that do.

 

Just put the 10W-40 in it. I run that oil without any issue across 4 different RX8's. Wont hurt it.

 

If you haven't gone through the used oil analysis thread go take a look.

 

Running 20w50 means never having to say you're sorry. . Be bold.

I run it without fear in this engine. I have posted many oil tests on this forum with my engine which show a favorable outcome in my opinion.

I am not sure where the current suspicion of thicker oils has come from. Many modern cars that call for 20w in the owners manual benefit from 40w in actual enthusiast use.

The belief that thick oil has been known to damage engines, should be the opposite. There are engines that show damage from thin oil, even new "modern" engines. I have never seen a teardown of an engine that failed from using a thick oil.


I continue to abide by the old fashioned viscosity charts published in manuals before they became political. Yes there are exceptions, but the RX8 is not one of them.

This is in Celsius:

 

Thanks for the chart. I've seen it once before but couldn't find this particular chart when I searched for it again.. Now I know where to find it. 👌