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The 8 calls for a 20 weight oil, and that is what you are proposing to use - no issue.
The only difference between a 0W, 5W, and 10W rating is the oils ability to flow at cold temperatures - the better it flows cold (lower the number) the better protection you will get when the oil is not yet warm.
StealthTL is right in that even though rated at 0W cold (measured at 40C), oil is still way thicker than when measured at operating temp (100C).
Most 20 weights oils are rated at around 8.5-9 cSt (thickness/flow resistance) at operating temperature (100C) and a 0W will be at around 45 cSt cold (40C) and a 5W will be at around 50 cSt (40C), so not much difference.
You see, a cold oil will always be way too thick to flow well when cold, not matter what the rating - one of the many reasons to take it easy on an engine until the engine itself and the oil are warm.
BTW - the AMSOIL 0W-20 (linky below) is very good oil!!
I know there was talk about a W20 oil being a bit too thin to meet Mazda specs. I think it was olddragger that mentioned this problem?
Misinformation! A 20 weight oil is a 20 weight oil is a 20 weight oil at operating temperature (100C).
The xW is only the flow rating (cSt) when at 40C, but all 20 weight oils are from 8.5-9 cSt at operating temperature (100C) and a 0W is NOT a thinner oil at operating temperature than a 5W or 10W.
The only reservations some enthusiasts have had in the past with 5W or even 0W oils is that they may use more Viscosity Index Improvers (VIIs) to achieve the 20 weight at operating temp in order to have the good flow at low temps.
VIIs last very well, but under extreme stress, can break down faster over time than the rest of the oil package - that is why some prefer a 5W20 over a 0W20 or a 10W30 over a 5W30 - because the 10W30 would use less VIIs and would be less prone under long oil changes to Shear (thin out).
This is is only an issue for persons doing 5000+ miles oil changes (dino) or 10000+ oil changes (synthetic) intervals. For our 8's, this is a non-factor as we should all be doing 2500-3750 changes due to the fuel dilution and partial oil change scenario.
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sorry if i word this like an idiot but i remember reading a while back that 20 weight oil is not thick enough at high temperatures for the renesis and that mazda made that the recommend factory weight to comply with emissions or some kind of automotive regulation?
also ive kind of switched around with alot of different oils.....it seemed like the car would run a little better when using a 30 weight as opposed to the recommended 30 weight. i am interested in running a 0w40 or 5w50......please let me know if this is totally wrong and why. thanks in advance.
I think you can get away with running 5w-20. i think the key factor is being diligent with the oil schedule, or if you notice the oil is degraded 'black' when checking the oil level.
I wonder how many people that drive their car hard '8000-9000' rpm accelerations daily, but don't check the oil level as recommended, or let the oil change go to 6-7000 miles.
I see the typical events with these failed rotary's is the daily hard driving, in combination of these factors cause attributing to engine damage and in the end result engine failure due to viscosity breakdown... to the point that the oil cannot maintain the protective film at 8000rpm.... running a 5w-20 instead of a 5w-30 i see would lend to an increased probability.
Last thought is i find it odd that Europe runs 5w-30 oil.... i switched the oil to 5w-30 Royal Purple as soon as i got it.
I wonder how many people that drive their car hard '8000-9000' rpm accelerations daily, but don't check the oil level as recommended,
Thats me.
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or let the oil change go to 6-7000 miles.
Thats not me, change mine between 1.5 K to 3K
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I see the typical events with these failed rotary's is the daily hard driving, in combination of these factors cause attributing to engine damage and in the end result engine failure due to viscosity breakdown... to the point that the oil cannot maintain the protective film at 8000rpm.... running a 5w-20 instead of a 5w-30 i see would lend to an increased probability.
could be could be. I mean the rest of the world seems fine with 5w-30, thanks to our great EPA stupid requirements.
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Last thought is i find it odd that Europe runs 5w-30 oil.... i switched the oil to 5w-30 Royal Purple as soon as i got it.
Same boat.
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I use 10w-30 Valvoline dino and BG MOA. I change every 1500 miles. I have had great results with the MOA. My oil injection lines from the MOP are so clean they appear transparent when completely filled with oil.
my OMP lines seems to be clean too.
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You can see the omp lines around the water pump pulley.
Yep, I see them. Curious why they are clear. Perhaps to be able to check flow, color or what?
My gut tells me that this clear tubing isn't as robust as a braided, black colored line that is usually run around a hot engine. Have they ever failed or do they need to be replaced periodically?
I am also of the opinion that 5w-20 is just a bit too thin.
I've switched to 5w-30 and 10w-40 synthetic in my MX-5 NC and it sounds much quieter. Am considering going to 5w-30 dino in the RX-8 at the next change.
Am also using Idemitsu premix.
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