Mazda RX 8 engine oil question

[steve1]

Need to do an oil change on a 56 plate rx8, the higher horse power model, ( if that makes any difference ), trouble is, I've been getting conflicting stories about what type/grade of engine oil to use.
One says that a tech. bulletin was issued around 06/07 actuating that a 10W/30 mineral oil was to be used, but my local motor factors are saying that according to there tech. details the right oil is 0W/30 fully synthetic.
Any one know for sure the correct oil.
Also, how much oil is left in the oil coolers, and the best way of changing this at the same time, as I understand that a valve shuts off and doesn't allow any oil out of the coolers once the engine is switched off, ( of course I stand to be corrected ).
Thanx.

[Defcon5]

I think you are supposed to use a mineral oil, not sure why though. Maybe because it burns better?

[wolves_wanderer]

5w/30 mineral oil is the one to go for. You will use about 4-4.5 litres in the oil change. There is no reasonable way to get at the other 4 litres held in the coolers and associated pipework but as the oil gets burnt through normal use it isn't a problem.

[steve1]

Forgot to add, the car does not get tracked, but might get the odd hard days driving, does the same oil still apply?
Also, I believe there is an oil breather some where that can become blocked, is there any particular way of cleaning this out.

[sherman]

I have always been told to use 5w/30 semi synthetic. The car has ran fine on it for 4 years now.

[wolves_wanderer]

steve1 said:

Forgot to add, the car does not get tracked, but might get the odd hard days driving, does the same oil still apply?
Also, I believe there is an oil breather some where that can become blocked, is there any particular way of cleaning this out.

Yep, same oil. The only similar issue I know about is that the dipstick can get "mayonnaise" in cold weather from short journeys, it is just condensation in the dipstick neck and isn't a problem but it can look a bit alarming. I believe there is a fix that dealers would sometimes do under warranty but I'm not sure how easy or otherwise it is. The best and most fun way to cure it is to go out on a long run and get some decent heat in the area.

Edit to add, if the hard driving is only occasional then make sure the oil is checked afterwards rather than just getting used to the oil consumption. The reason is that the oil is metered out by the ECU and it will use more when driven hard.

sherman said:

I have always been told to use 5w/30 semi synthetic. The car has ran fine on it for 4 years now.

I think all 5w/30 are semi-synth, I just meant mineral to distinguish from synthetic, I should have been clearer.

Edited by wolves_wanderer on Wednesday 14th March 14:16

[sherman]

wolves_wanderer said:

steve1 said:

Forgot to add, the car does not get tracked, but might get the odd hard days driving, does the same oil still apply?
Also, I believe there is an oil breather some where that can become blocked, is there any particular way of cleaning this out.

Yep, same oil. The only similar issue I know about is that the dipstick can get "mayonnaise" in cold weather from short journeys, it is just condensation in the dipstick neck and isn't a problem but it can look a bit alarming. I believe there is a fix that dealers would sometimes do under warranty but I'm not sure how easy or otherwise it is. The best and most fun way to cure it is to go out on a long run and get some decent heat in the area.

sherman said:

I have always been told to use 5w/30 semi synthetic. The car has ran fine on it for 4 years now.

I think all 5w/30 are semi-synth, I just meant mineral to distinguish from synthetic, I should have been clearer.

The dipstick on my rx8 goes this way every winter but always clears up with the warmer weather and the start of the PH runs.

[steve1]

Just to update this, have spoken to a company called Hayward Rotary in Newbury, and they have said either, 10W/40 mineral or 15W/40 mineral, and to change every 6K miles.

[Lee_sec]

I've used 5w/30 Semi Synth in mine for years... never had any problems...

changing every 6k? it uses approx 1/2-1 litre every 1000miles so you'll be doing that through general use anyway?!

[deeps]

Mineral is the norm, apparently Mazda don't recommend synthetic because back in the 70's they had problems with early synthetic oils corroding the rotor seals. Things have moved on since then, but mud sticks.

I've had several rotaries, and something I recommend is a splash of synthetic 2 stroke oil in the fuel tank at every fill up which helps lubricate the tips.

[wolves_wanderer]

deeps said:

I've had several rotaries, and something I recommend is a splash of synthetic 2 stroke oil in the fuel tank at every fill up which helps lubricate the tips.

About 150ml per tank normally, more for track use.

[davidglanza]

i have an rx7 and i use 10w40 mineral oil

[hygt2]

Castrol Magnatec 5w30 semi-synthetic was fine on my RX8 231, it is just the basic Ford oil used for Zetec.

You need a fairly basic oil that burns cleanly. Fully synthetic oil is harder to breakdown and burn cleanly without residual that may coat up the catalytic converter.

[liner33]

steve1 said:

Just to update this, have spoken to a company called Hayward Rotary in Newbury, and they have said either, 10W/40 mineral or 15W/40 mineral, and to change every 6K miles.

They are the experts, so personally I would take their advice

[rotarymazda]

Good quality mineral oil that burns completely (that's the key).

I was at an engine (re)builders a couple of weeks ago and he showed me the effects of his customers running semi-synthetic. The results of incomplete burning were a brown residue on the housing, the apex seals then start to hop across it and then chatter marks develop after that. End up with apex seal wear and low compression.

I use mineral oil with a separate premix supply managed by a OMP controller.

[steve1]

Explain to me a bit more about the premix that people are running.

[Ali_T]

RX8 oils are confusing. Mazda recommends 5W 30 Dexelia Ultra, their own brand. It says it's synthetic but it's not, it's regular oil but "hydrocracked". Castrol Syntec 5W30 is similar. Rotaries don't actually do well with full synthetic oils.

[wolves_wanderer]

steve1 said:

Explain to me a bit more about the premix that people are running.

There are numerous and lengthy threads on the owner's club website but the general gist is that 150ml (or thereabouts) of a good quality ashless, 2 stroke oil (I use motul 710) in the fuel adds a bit more lubrication and helps sealing in the engine. There has been some evidence from teardowns that carbon buildup is reduced as well.

Having used it for a while now I have noticed a difference in the feel/smoothness of the engine and strangely the sound is less "raspy". I believe engines have been dynoed as slightly (ie within a % or 2) more powerful, but the main difference is the smoothness which is noticeable. For a couple of quid a tank it isn't doing any harm. Mine has 63k on the clock and starts within a second hot or cold, and that is with the older, slower starter motor.

[stan riley]

I have owned a Mazda RX8 for six years now. 55,000 miles on the clock serviced every 12 month regardless of mileage and always used castrol GTX 5w x 30 fully synthetic. Engine is perfect and is really powerful with no problems. I wind it up each week. This oil works for me. Hope this helps.

[Salesy]

I regularly race and track my RX8, i use mineral oil as it burns properly. Oil is changed every 3k as it works a little harder than most.

Funnily enough my compression is in the low 5s which according to Mazda is a completely shot engine, but it starts on the button hot and cold and still pulls very well.