ProtoConVert

is it "old" oil or is it X% oil contaminated?

S3/P3/E2

Yeah, no argument w/ you there Nubo. I think you're right about "what's left behind." My biggest concern would be the metal particles, etc. suspended in the "old" oil that are still there even in a lesser number due to the half-an-oil-change procedure.

Nubo

'cause it ain't in the owners manual and few owners received the "guide"

VelocityRedRX8

More like % oil contaminated. It's just a dilution effect. The fraction original oil (assuming no other additions) remaining as a function of the number of oil changes is just: 1/2^n. This also assumes a 50% mix. Under these conditions there's only about 3% 'original' oil remaining after 5 changes.

But, in reality the car uses oil. Mines uses about 1qt/1000 miles. If I change every 3000 miles I will have added 3qt additional oil. Frankly, I think the car's oil stays pretty clean as a result. Constant turnover.

S3/P3/E2

...and then the mathematicians showed up to embarass "the feeble-minded ones." :D

Good to know someone's got a 10 lb. brain around here.

Tamas

iTrader: (1)

Honestly, I don't intend to stir up some sort of a religious war about oil change intervals - but I fail to understand why would that be beneficial when Mazda recommends a 7500 mile interval...
I intend to stick to their recommendation - there has to be a reason why did they come up with that specification.
IMO changing oil every 3000 miles will only make thei oil companies rich (and eventually the service stations performing the changes).

brothervoodoo

Depending on driving conditions they also have 5,000 mile interval. Since I got free service that's the one i'm using plus I'm throwing in a fresh quart every couple thousand..

Nubo

Many other vehicles specify a 7500 mile change interval, but their oil changes result in close to a complete change-out. With so much oil remaining in the RX-8, you would have to change more frequently to approximate the effects of a 7500 mile change for other cars.

I suppose used-oil analysis will tell the real story. Until then I'll err on the side of caution, especially with tales of the engine running abnormally rich.

Economically I'll mitigate the effects in 3 ways. For one, I've decided to run conventional oil instead of the synthetic I've been running in my current vehicle. Secondly, no service stations are going to get rich -- oil change is DIY. Third, I'll change oil filter every other oil change.

Vrimmick

Hey guys,
I just had my oil changed in my rx8. On my way back from the dealership I looked at the sticker and it says Quaker State 5w20, which is what is should be. But then I look closer at the sticker and it says "synthetic blend"??? What the hell? Aren't they supposed not to use synthetic??? I know it is not fully synthetic oil (it is just a blend) but still it does not burn so easily... I guess I have to call them back and make sure that they know what they are doing.

Vrimmick

Ok guys,
I just called them. They say 5w20 quaker state synthetic blend was approved by mazda for rx8. And this is the oil they specifically got for rx8! End of story.
I guess I just replied to my own message. Well hopefully somebody will find it helpful.
Thnx

cruzdreamer

Quick response you got too!

mikeb

very interesting

I wonder if they are just saying that because they made a mistake

khoney

The owner's manual is gospel - it has all of the technical specifications. The guide is an overblown sales brochure, IMO.

Daverx

btw i m using 10w50.....

syntrix

Exactly!!

Read my comments in the thread. MNAO has not officially notified owners that you can't use synths. Sure the brochure is great, and I wish that everyone got one with their purchase! Unfortunately that's not the case. But we have this great forum to share this kind of info

compaddict

Don't we also have oil metering to think about? If the system is set up for a specific viscosity and we you something thicker won't less oil be metered?

Just a thought.

Vince

RobDickinson

I guess it depends on expected temperature ranges.

In UK the cars are supplied with 5w30.

x28

Anyone know what engine oil we should use for winter time? Still 5W20

compaddict

Must not be critical then. Thanks!

Vince

jonalan

I suggest a follow up phone call to MNAO to see if 5w20 Quaker State Synthetic Blend IS approved by Mazda for the RX-8.

If so, great! If not, looks like a trip back to the dealer for another oil change (on the house).

KKMmaniac

I guess the next step less viscous than 5w-20 would be 3-in-1 oil? (yes, I'm joking)

jafosrx8

IMHO, none of the differences between the Renesis & previous rotary engines would negate the rational behind not using synthetic oil. My understanding is that the Renesis requires less oil to be sacrificed into the combustion chamber but there still is an oil metering pump so some oil is still sacrificed & synthetic oil leaves a resin like residue when burnt. One thing that I’ve learned as I’ve aged is to trust my judgment…I’ve been burned (no pun intended) many times by ignoring my judgment in favor of one from an individual possessing greater authority or credentials.

WARNING – Characteristic Red Neck Sounding Rant - WARNING

100% Dino for me regardless of what some guy in a lab coat sez’.

deadrx7conv

Good luck finding ANY 5w20 oil that is NOT partially synthetic.

In order to pass the extended/double sequence testing, most are blends.

Synthetic oil burns just as easily as any other oil. Spill some on the exhaust manifold. This is an easy way to compare oils. Most synthetics burn cleaner than mineral oils.
If you don't believe this, BURN SOME YOURSELF!

deadrx7conv

5w20 provides the same protection as any other weight oil. The important thing is that the engine must have some type of control over oil temp.

If the temp of the 20wt oil is 20F cooler, then it is as thick as the hotter 30wt....... How many oil coolers do you have? foreign market cars have????

Also, these oils pass more strict testing for use in Mazda/Ford/Honda applications.

Gord96BRG

Bingo! I wonder if those who say synthetics don't burn as clean have actually ever seen results of combusting synth oil vs. dino oil. It's the exact opposite - dino leaves a sludge if anything does.

Mazda won't recommend or approve (or disapprove) any specific brand of oil, or they leave themselves open to lawsuits. Further, US federal law prohibits manufacturers from requiring any specific brand of fluid or lubricant for warranty purposes unless they provide that fluid for free - Ferrari has run into that already, where they tried to require owners to pay $60 per quart (yes that's right, sixty dollars per quart) for a special Shell synthetic oil for the Enzo, and said that warranty would be void if they didn't use the special Shell oil. Very quickly Ferrari North America was reminded that if they required only that oil, and that generic oil meeting a specification (say, the way Mazda specifies API SL spec 5W20 for the RX-8), then they would have to provide it for free to Enzo owners. Long and short of it is - Mazda can NOT void a warranty on any engine that has followed maintenance intervals with the specified oil, that specification being API SL 5W20. Period, no mention of dino or synthetic. If your synthetic oil of choice meets API spec SL, it's fine.

Regards,
Gordon