RIWWP

iTrader: (2)

Some place for new members to discuss oil all they want.

I will delete any posts that are contrary to the user code of conduct.

I will also move new member oil posts from other threads into this thread.

If you are a new member and are looking at this thread for information, please take all information in it with a large grain of salt. There are a million opinions on the subject and you will NEVER find a consensus.

For lab tests of specific oils, please see the Used Oil Analysis thread here: https://www.rx8club.com/series-i-tec...m-here-184241/





Here is my opinion, feel free to put your own opinion below.

https://www.rx8club.com/new-member-f...t-here-202454/
Which oil to use
The most debated question in the community, bordering on a religious war, so I won't try to cover every point here.

It boils down to deciding for yourself.

Some go with 5w20, to stay with Mazda's recommendation in North America. Some go with 5w30 to go with Mazda's recommendation outside North America. Others go to 10w40 or even 20w50, the most common weights among RX-7s. The general argument revolves around if 5w20 is too thin or not. Typically, you want to go with a heavier weight oil (higher numbers) the hotter the environment you live in. Many manuals outside of North America state something to this effect. So research up on it, and make your own decision.

Dino vs synthetic is another hot topic, with the main argument revolving around if the strength of the synthetic is worth the cost, and if there is any better burning (or not better burning) than dino oils, and if any deposits are left behind that could increase engine wear. Mazda only recommends non-synthetic, but does not require it. Your decision.

And yes, all weights of oils mix with all other weights of oils, roughly averaging the numbers. Half 5w20 and half 5w40 is roughly 5w30, for example. Not precisely, but close enough. Dino also mixes entirely fine with synthetic.




And you know what the kicker is at the bottom of this whole oil debate pile?

It doesn't really matter

Fresh oil on regular changes is far far far more important than ANY of the above attributes. And the only impact that crankcase oil type and viscosity lubrication has on your engine's lifespan is bearing wear, which is not a severe concern for us, since we have numerous other methods of engine failure that have nothing to do with oil attributes!

Outside of lubricating the e-shaft bearings and being available for injection into the combustion chamber (where none of the attributes above matter at all), the oil's benefit is a secondary method of assisting to keep our engines cool. Oil is fantastic for transporting heat out of the engine. And all types and viscosity do that equally well, or as close to equally as won't make a tangible difference.

There are claims that synthetic doesn't burn as cleanly as dino.

Well, are you really going to argue that filthy dirty 4-stroke dino oil burns cleaner than filthy dirty 4-stroke synthetic oil? NEITHER of them were meant to be burned, and crankcase oil is very very filthy. If you are so concerned about how clean burning your oil is, then get a SOHN adapter and start burning clean 2-stroke! Then you can pick the oil that you want for the high stress, high rpm, high sheer environment of the e-shaft bearings.

So if oil weight matters to you, then do some reading on the various opinions, find an opinion you somewhat agree with that is made in reference to the climate you drive in, the drive style you do, and your budget, and go with that.

McBamBam

Notes

Engine oil capacity
Oil replacement: 4.2 L
Oil and oil filter replacement: 4.4 L
Engine overhaul: 5.6 L
Total (dry engine): 7.0 L
Oil pan drain plug tightening torque: 29.4-41.2 N*M {21.7-30.3 ft*lb}

Mazda 2009 Workshop Manual, 01-11-4 specifies 5W-20 ILSAC certified oil.

Mazda appears to have stamped 5w-20 in every single mention of the word oil. It recommends it in Canada and every other place in the world whether it gets cold there or not. Personally I wouldn't just assume that it is okay without having some sort of documentation that is reliable proving that it is okay.

Let me give a example; using regular gas instead of super premium in your RX-8. I have found many people on this forum who have said it is just fine and they have noticed no engine knocking and highly recommend doing it. But, let me analyze this a bit on what that action does.

1) I save money whenever I buy gas. Positive.
2) Risk of engine knocking. (even if they don't notice because they might not be listening for it with the music off and no distractions every minute they drive) Negative.
3) Higher probability that my engine will not last as long as if I used premium. Negative.
4) Racing guys do not use regular gas... they try to get as high octane as is possible. I use gas that costs $16 a gallon when I motocross. Using anything other than $16 gas results in loss of horsepower. Negative.

But hey... you save maybe a whole dollar a gallon! Why... after 4 gallons you could purchase a free gallon of milk! free milk > side effects. I mean it's not like we purchased a sports car or anything right? This is a 4 door family car anyway and I bought this car because it was cost effective and it is very fuel efficient.

So... if your looking for someone to say you can do it. You can do it and your car will most likely not spontaneously explode upon contact with viscosity other than 5w-20, but I think you already knew that. To answer your question more directly... a normal drain will not drain about 2.6 L of oil from your car. Thus you will mix your oil with nearly 60% still being the oil you used before. If you were to fill, drain 2-3 times while starting your engine to mix up the oil in between you might get that number down significantly. (7L - 4.4L (normal oil change assumed to be oil and oil filter replacement) = 2.6L. 2.6L/4.4 L= roughly 60% being the 2.6L oil present before oil change, source Mazda 2009 Workshop Manual).

My only concern is that I have not seen any reliable data saying that changing from conventional to synthetic or changing its viscosity from 5w-20 to anything else has a positive benefit in a rotary engine such as ours. So if someone would like to correct me and has that documentation or some sort of logical argument indicating a positive result from using anything other than 5w-20 conventional specifically in our rotary engine (not a aircraft engine designed to operate under different conditions) then let me know! I'm sure there must be documentation on this somewhere apart from Uncle Jim Bob's testimonial... but I wouldn't just assume because some side effects take time before they are noticeable and this engine does use oil to lubricate it's seals. Improper lubrication of seals = eventual loss of compression + not many people know how to work on rotary engines = high cost of repair or engine replacement.

My 2 cents

sintoni

This has been discussed for ages.

Yes 5w20 is perfect for winter driving, however, I am not in the US, as I live in Australia, and it is approaching the summer right now, so I think I will be switching to 10w40 for the summer time.

All I want to know is it okay to do just normal flush when I am switching to another type or viscosity of oil.

paimon.soror

iTrader: (15)

It has been discussed adnausium and proven by many of us (myself included) that you can easily get out 5+ quarts of oil using a pump (like a mityvac)

And check out the UOA thread for some evidence of the shortage of wear metals, sustained viscosity numbers, and lack of absorbed moisture for those of us who have been using synthetic oils vs conventional counterparts.

ken-x8

Since my post count is lower than RI's or Paimon's, I guess I qualify to contribute to this new member thread. Just two points on what Mazda has to say.

1. There is a version of the shop manual that lists almost every weight of oil from 5w20 to 40 (or is it up to 20 w50?), without saying when to use what.

2. There's a chart in the Australian owner's manual that shows which oil weight to use at what temperature. (I believe the chart is in RI's new owner thread.) In temperate climates they all overlap.

Ken

PS - Sintoni - just change it. No need to flush. They're all compatible.

Teraxo

Hey guys!
I was having a question about the engine oil for my 2004 Rx 8.
I've been looking at the Mazda original ultra 5w-30 oil, however on the description it sais "for all diesel engines, and the rx8".
My question is now if it is possible to put oil for a diesel engine in a petrol car?

I realize this maybe a dum question but I want to be shure before I put the oil in.

Thanks!

Ross Roberts

Hi all,

Just bought an 05 RX8 yesterday,Yay!

Off to buy some oil today, however although the previous owner said he used 5W30 oil, he has no idea what brand or if it was synthetic/mineral.

Going to book her in for a service/health check as soon as i can but in the mean time I want to top up the oil.

My question is, are there any issues with mixing oil types? eg mineral with synthetic? I will be looking to by 5w30 mineral oil.

Thanks.

BigCajun

iTrader: (1)

No problem.

Ross Roberts

Thanks Cajun.

ken-x8

As long as it meets the API and/or ILSAC ratings specified in the owner's manual it's OK.

Ken

RIWWP

iTrader: (2)

You can use a diesel oil if you do not have a cat in your exhaust system. If you have a cat, don't use diesel oil. It has additives that cats are not equipped to handle. Not as much of a problem in a car that doesn't burn oil intentionally.

OR, add a SOHN adapter to only burn clean 2-stroke, and then use the diesel oil without harming your cat.

jcrane81

hi every one,
need a bit of advice, my last oil change was done by mazda, its due another oil change but going to do it myself, what oil do you recomend, was going to use mineral oil but want to get the best mpg out of the car will the oil I use effect the mpg? so whats the best oil to use. thanks



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200.mph

iTrader: (9)

there is no solid answer. everyone will tell you a different type/weight. i use dino 10/30 valvoline. i only drive my car in the summer tho. where do you live?

Superman99

Royal Purple 5W20...burns just the right way. I swear by the stuff.

jcrane81

live in london, england, the oil in there now is dexelia, I think 5w30 thats what mazda used but expensive so was going to use cheap mineral oil as it burns easier


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9krpmrx8

iTrader: (46)

Not in an RX-8. Used oil analysis done by Royal Purple themselves show differently, just look in the UOA thread or ask Paimon. They are great at marketing though.

hirpm

My Mazda dealers "rotary specialist " put mobile 1 synthetic blend in my reman engine, he recommended it. They had installed the reman 60 miles prior to me purchasing the car. I have read the debate of synthetic v non synthetic until my eyes were bleeding!
I guess ill stay with it, at least until next oil change, if I can see a better choice ill go with it. I premix as well.

Harmz_Rx8

Hi guys, just wondering what oil to get. I want to change my oil tomorrow but I'm not sure on which oil to buy as I've seen on the net that we're not meant to use fully synthetic oil because it doesn't burn properly.. Thing is I'm from London Uk and NO where sells conventional oil soo it has to be okay right? I'm thinking of getting: Castrol Mazda Magnatec Fully Synthetic 5W30 Engine Oil (4 Litre) | Euro Car Parts UK

Let me know what u all think asap. Thanks!

J8635621

iTrader: (10)

Doesn't matter. There are far more important things to worry about. Synthetic is a-ok

RIWWP

iTrader: (2)

From the New Owner's thread:

https://www.rx8club.com/new-member-f...4/#post4533706

ken-x8

No synthetic for me. I prefer to use the real stuff.

Ken

Arca_ex

iTrader: (10)

SOHN + Synthetic will always be the best combo.

shiryu7

iTrader: (2)

For what it's worth, conventional, for the fear that synthetic doesn't burn as well, has never served me wrong.

RIWWP

iTrader: (2)

Well, are you really going to argue that filthy dirty 4-stroke dino oil burns cleaner than filthy dirty 4-stroke synthetic oil?

tmrx8

iTrader: (1)

Definitely loving the synthetic in my rx8
If you do some searching, lots of guys are having some success with 0w40 Mobil 1 synthetic oil.
I only have good things to say about the Mobil 1 0w40.....other than price...enjoy some more engine longevity!