RotoRocket

iTrader: (1)

Yes. I have searched the oil threads. Lots and lots of info.

But does anyone have the official Mazda rationale as to why U.S. owners (only) should use 5W-20 weight oil?

I could see 10W-30, or even 5W-30, but 5W-20?

Ericok

The EPA requires that manufacturers strictly recommend the oil that was in the engine when the vehicle was emisson rated. In the US, manufacturers use the thinnest oil they can in order to meet warranty requirements and get a good gas mileage rating. A good mileage rating helps their Corporate Average Fuel Economy (CAFE) which is a fleet average mandated by law.

RotoRocket

iTrader: (1)

So, in other words, 5W-20 isn't recommended because of anything inherent with the rotary, but because of emission and EPA fuel consumption ratings?

And 10W-30 would provide better protection, even if mpg would decrease?

ZoomZoomH

iTrader: (1)

actually, the current batch of 5w20 oils available are very good, sometimes providing even better protection than higher viscosity oils.

ZoomZoomH

iTrader: (1)

think of it this way, Mazda wouldn't recommend an oil grade that is INFERIOR than other grades JUST for emission requirements, it's gotta be *at least* comparable, if not superior, to the thicker oil in terms of protection

ZoomZoomH

iTrader: (1)

remember, long time ago in a galaxy far far away, people thought 30 weight oil was too thin :o

KYLiquid

it comes down to the ambient temps that you drive the car in, pick an oil that is suited better for you climate. Hotter areas would want to use thicker oil, while colder areas use thiner.

The stock oil weight isnt bad, but might not be the best pick for your area/driving habbits (lots of high rpm, low speed).

I use 5w30 but thats just cause its easyer to find in the brand I use thatn 5w20. I used to run 0w30 in my miata....no problems.

RotoRocket

iTrader: (1)

I'm in Michigan, so the range of temperature is pretty extreme here (anywhere from 100 f in the summer, to -10 f in the winter).

I have no problem using the 5W-20 in the colder winter months.

But since I bought this car for the long run, I don't want to do anything contrary to Mazda's maintenance schedule and recommendations, even if 10W-30 might be my preferred choice in the summertime.

Nubo

I chose 5w30 early on because at that time the early flashes were too rich and fuel dilution was a concern of mine. It also happened to be a more commonly available weight for the oil I use. I may change to 5w20 now that the flooding issues are past. Members who've listed their used oil analyses recently haven't shown fuel dilution to be a problem. A smaller gap between the 2 numbers means less viscocity modifiers were needed to blend the oil, which is generally a good thing (5w30 = gap of 25, 5w20 = gap of 15).

rotarygod

5W20 is fine for naturally aspirated street engines. Once you get into forced induction I'd switch to 20W50.

Ericok

If you do a search, you'll see that 5W-30 is Mazda's recommended oil in every market except North America - but then, maybe, you can't get 5W-20 everywhere.

Dragonfc3s

Actually the DVD that came with my car recomends the use of 0W-20, I'm in Japan (Jspec car) and have yet to see 0w-20 oil for sale anywhere...

Ericok

The following is quoted from EPA letter to manufacturers dated March 2, 2004 entitled: Use of GF-4 Engine Oil in Certification and Fuel Economy Test Vehicles. It basically says that if you used 5W-20 in testing, the Owner's Manual must clearly and unambigously say it is to be used.

Attachment to CCD-04-07 Approval Criteria for Use of GF-4 Oils in Certification and Fuel Economy Test Vehicles 1. Owner's Manual Language The manufacturer provides instructions in the Owner's Manual that clearly and unambiguously identify that GF-4 engine oil (identified by the presence of the American Petroleum Institute (API) "Starburst" logo) of a specific viscosity grade ( 5W20, 5W30, 10W30) is to be used in the vehicle's engine under normal ambient temperature and driving conditions. If the API starburst logo is used in the owner's manual in lieu of reference to GF-4, the manufacturer should include a brief explanation of its meaning. If the Owner's Manual employs a graphical depiction of oil viscosity vs an ambient temperature range, inclusion of any qualifier word, ''preferred for example, associated with the oil viscosity is considered to introduce ambiguity into the instruction, and disqualifies the use of GF-4 engine oil in test vehicles. It continues to be appropriate for a manufacturer to specify the use of a lower viscosity grade in extremely low ambient temperatures where the normally specified oil may not flow adequately. If a vehicle owner wishes to use a synthetic, or partial synthetic oil, EPA does not expect a vehicle manufacturer to preclude use of such an oil if it meets all vehicle manufacturer requirements.

Ericok

I've seen 0W-40 in the US. At Walmart no less.

crossbow

Some discussions on the topic.

Viscosity charts are no longer valid for temperature recommendations. Oil technology has advanced to the level where they are now obsolete. Most current 20 wt oils are superior in additive packs, base stock's, and sheer stability over most 30 wt oils.

Going too thick an oil is also just as bad as going too thin. Viscosity is not a measure of protection!

RotoRocket

iTrader: (1)

That's amazing.

I had no idea there was anything even out there such as 0W-20 oil.

Does anyone care to explain to me how this could possibly protect the engine?

rotarygod

Why wouldn't it? The only time oil doesn't protect the engine is when there is none. Even a thin oil is a barrier between the seals. Lots of people run really thin oil with no issues.

Dragonfc3s

They taught me in school that zero ='s nothing, so once the engine warms up does my oil disappear. :D

crossbow

You know that some companies have experimented with 0w-5 oils... I bet we'll see them in 10 years or so. Technology changes. You either adapt, or get made fun of.

Oh ya, all those links. Well the rx8forum screwed them up. So just go to this link, and click all the links posted by Racer X-8
https://www.rx8club.com/showthread.p...ight=viscosity

RX8FOREAL

I was running 20w50 in the summer with the turbo. Since I live in New Jersey, I am concerned about the winter and was planning on using 10w30 Amsoil. Any thoughts ?

crossbow

I suggest stop guessing what oil you should use on your car, and find out what a tribologist thinks.

Terry Dyson has worked with Mazda motorsports teams in the past, and a well respected member of the BITOG community.

Send for a free test kit (the analysis still costs).
http://www.blackstone-labs.com/dyson_analysis.html
http://www.blackstone-labs.com/free_test_kit.html

Alot of people find, that after proper oil analysis, their best results are usually with an oil they thought was completely wrong for the application.

Of course you could just take random comments from forum members for your recommendations.

Off the top of my head, you could probably run redline 10w-30 year round, with good wear numbers. Redline's 10w-30 most likely has a higher HTHS # then the 20w-50 your using in the summer.

rkostolni

Rotary God, you really recommend that thick of an oil for FI users? You don't think the startup wear will be greatly increased from using such a thick oil? And if we do mostly short trips, I'm not sure that most of the time the engine would be at the proper operating temp to thin out the oil fully.
Redline makes a 5w40 oil, wouldn't that be better since the turbo doesn't effect the oil temps when the engine, and hence turbo are both cold (engine startup)

yiksing

Wouldn't thin oil burn away too easily or it doesn't matter since the car is already burning them?

rotarygod

Don't think that 20W50 is like mollasses. It isn't. It is still a 20W oil. It just behaves thicker when hotter. 20W50 is what is used by most people in rotaries, high and low power. I am actually different in that I run a thinner 5W20 in my 13B nonturbo. The Renesis is the first rotary to use 5W20 from the factory. I actually use to use 20W50 in my car. I only use 5W20 because someone said it would kill my engine. When he couldn't prove it, I thought I'd try to. It hasn't. Not even close. 20W50 is actually what is most widely accepted in the rotary. In truth nearly any weight oil you can find will work without any issues just fine. I think it's funny when people argue on 5W20 vs 5W30 or 10W30. They are all just fine and safe. You could see some small power differences or oil temp differences though but they all do their jobs.

Thick oil, thin oil, if you are having issues with it burning away while you are driving, you've got oil cooling issues. That's WAY too hot! +300*F If you are referring to the oil metering system and the small amount that burns in the combustion chamber, combustion is over 2000 degrees F so each will burn away just like the other.

I spoke to Dave at Royal Purple the other day. He has raced rotaries in GT2 and GT3 for years. He used to run 5W20 in a 13B bridgeport race engine with no issues when everyone else has been saying it was too thin.

RotoRocket

iTrader: (1)

I've been doing some research, and correct me if I'm wrong RG, but it would appear that Honda and Ford/Mazda are likely recommending 5W-20 motor oil in an attempt to boost their fuel mileage standards under the EPA testing protocol.

From what I can gather, the theory is that 5W-20 may, under the most ideal testing circumstances, boost fuel efficiency by 2-3%, due to lower resistance/friction.

If that's true, wouldn't 5W-30 be better inasmuch as it has a much broader temperature range suitability?

I realize the differences are subtle, as you have said, but 5W-30 is also easier to find in more brands.