2012 Mazda 3i Skyactiv, Castrol OE 0W-20, 7k

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badtlc

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This is the first UOA of my skyactiv 3. I bought the car with 15k on the odometer. This UOA sample was taken at 22,000 miles. The oil was not changed. No makeup oil. OEM air filter and oil filter. Lab was SOS out of Wichita KS via loca CAT rep.

Oil will be changed at 7.5k with PP 0W-20.

uoa1mazda3.png


TBN will be added soon and hopefully flash point & fuel content. Not that it matters, though, it is quite apparent fuel dilution is not an issue for me and this DI engine. I honestly think the reason for low fuel dilution is using exclusively premium gasoline. This engine is designed to enrich the A/F ratio to cool the combustion chamber and prevent knocking. I think the premium allows the ECU to lean out the ratio.
 
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Is the ECU really that smart, or does it simply affect timing based on what the knock sensor hears, like most cars?

I don't know much about the Skyactiv engines. Your statement that this engine iDoes it recommend higher octane for better performance? If not, then you're most likely wasting your money. Your low fuel dilution probably has nothing to do with the octane used, either.

As a side note: many ECU's employ high-load enrichment (i.e., in open loop fueling) to keep temps down. I don't see how this would LOWER fuel dilution or have anything to do with octane requirements. If aggressive enough, then it would be counter to your theory that higher octane is necessary, since octane doesn't noticeably affect fuel trims.
 
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Originally Posted By: gathermewool
Is the ECU really that smart, or does it simply affect timing based on what the knock sensor hears, like most cars?

I don't know much about the Skyactiv engines. Does it recommend higher octane for better performance? If not, then you're most likely wasting your money. Your low fuel dilution probably has nothing to do with the octane used, either.

As a side note: many ECU's employ high-load enrichment (i.e., in open loop fueling) to keep temps down. I don't see how this would LOWER fuel dilution or have anything to do with octane requirements. If aggressive enough, then it would be counter to your theory that higher octane is necessary, since octane doesn't noticeably affect fuel trims.


Previous skyactiv UOAs using 87 octane showed fairly severe fuel dilution, even one that was almost all highway driven. This oil was all through winter with a fair amount of cold starts. Mazda only recommends minimum of 87 octane. The same engine runs on equivalent 91+ over seas. I see better MPGs with the premium and will not be running regular anytime soon.

The skyactiv engine runs rich in "closed" loop mode to cool temps in order to prevent knock while running lower octane during higher compression. Running a higher octane doesn't require the combustion chamber to be cooled as much to prevent detonation or knocking.
 
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Originally Posted By: LT4 Vette
Can you post pictures of your car ?

I thought these engines have a high compression ratio.


I guess I could. I don't have any right now. It is just a basic titanium 4-dr sedan. Completely stock like you see on Mazda's website.

The compression is 12-13:1. I can't remember if it is 12 or 13.
 
Here is the code version. Hope this works.

Can anyone help interpret the Oxidation, Nitration and Sulfation numbers? I'm new to these.
Code:
Code:

OIL Castrol

OE 0w20

MILES IN USE 7k

MILES 22k

SAMPLE TAKEN 5/12/13



ALUMINUM 2

CHROMIUM 1

IRON 11

COPPER 8

LEAD 1

TIN 1

MOLYBDENUM 685

NICKEL 0

MANGANESE NT

SILVER 0

TITANIUM NT

POTASSIUM 0

BORON 31

SILICON 8

SODIUM 4

CALCIUM 1716

MAGNESIUM 17

PHOSPHORUS 684

ZINC 821

BARIUM NT



SOOT 0

WATER N

ANTIFREEZE N

OXIDATION 19

NITRATION 8

SULFATION 28

VISCOSITY@100C 8.8

TAN 1.50

TBN COMING SOON

FUEL COMING SOON

FLASH POINT COMING SOON
 
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A quick search shows that USDM has 12:1 CR, while EDM has 14:1. There's your premium requirement right there, I think.
 
Yeah comparing the octane requirements between the US and Europe is misleading because they have different compression ratios.
 
Originally Posted By: gathermewool
A quick search shows that USDM has 12:1 CR, while EDM has 14:1. There's your premium requirement right there, I think.


No, the mazda3 cannot have the 14:1 due to the exhaust header. Only the CX-5 can have the 14:1 at this point. And it doesn't matter. The whole concept is the same regardless of location according to Mazda engineers. The NA syactiv runs rich A/F ratios in closed loop to maintain cool combustion chamber temps to prevent knocking while running 87 octane. In europe, the same applies so that it doesn't require even higher octane due to the higher compression. That comes straight from mazda.
 
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Good to hear that fuel dilution isn't a problem for you. I changed my oil on May 10 and I'm waiting for my Blackstone results. They got my sample today so I should know soon whether my fuel dilution % went down.
 
Originally Posted By: derekivey
Good to hear that fuel dilution isn't a problem for you. I changed my oil on May 10 and I'm waiting for my Blackstone results. They got my sample today so I should know soon whether my fuel dilution % went down.


Good luck to you! Hope it comes back well.

I'm only assuming my fuel isn't an issue since 8.8 cSt is just a touch higher than the published spec and the oxidation seems fairly low. So I hope it isn't the result of thickening, but I could be completely wrong.
 
OP, please clarify exactly which oil this is. When you say Castrol OE, I'm not sure what you mean. Based on the moly number it looks like the over the counter Mazda High Moly oil. Which Castrol oil is OE?
Thanks.
 
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Finally got the TBN measurement. It came back at 3.9. Very stout showing for this Castrol oil if I do say so myself.

Mods, is there a way to add this to my previous post where i used the "code" format?
 
Originally Posted By: badtlc
The same engine runs on equivalent 91+ over seas.


I don't mean to nitpick, but the overseas engines that run higher octane have 13:1 compression rather than the 12:1 we get here to be able to run on regular gas.

The CX5 gets the 14:1 overseas and 13:1 here because that body style has space for the Skyactiv exhaust manifold.

I am not compulsive enough to mess with oil analysis. I just did my second oil change using the OEM filter and Mazda GL-5 oil. The level on the dipstick remains constant for the entire OCI. I know that may not mean much.

I guess I am just not as into the whole oil thing as you guys. The Mazda oil is high moly and high VI and not an awful price. The filters are reasonable and appear to be well made (one was cut open in a post here). Done and done.
 
It isn't about the oil performance as much as fuel dilution. The fuel dilution leads to intake valve deposits. The UOAs help verify my theories about how to improve performance and reduce fuel dilution in the Mazda skyactiv-g 2.0 engine. And so far, it looks like I am right.
 
Originally Posted By: badtlc
It isn't about the oil performance as much as fuel dilution. The fuel dilution leads to intake valve deposits. The UOAs help verify my theories about how to improve performance and reduce fuel dilution in the Mazda skyactiv-g 2.0 engine. And so far, it looks like I am right.


I thought the intake valve deposits were from not having fuel passed by them because the fuel injectors are not in the IM any more?
 
Originally Posted By: Miller88
Originally Posted By: badtlc
It isn't about the oil performance as much as fuel dilution. The fuel dilution leads to intake valve deposits. The UOAs help verify my theories about how to improve performance and reduce fuel dilution in the Mazda skyactiv-g 2.0 engine. And so far, it looks like I am right.


I thought the intake valve deposits were from not having fuel passed by them because the fuel injectors are not in the IM any more?


That is why you can't clean the intake valves. A signficant source of the deposits is fuel getting into the oil. When the fuel gets into the oil, it increases the volatility of the oil and in turn increases vaporization of the oil/fuel mix which then gets sucked into the PCV making its way to the intake and then condensating on the intake valves forming the deposits.

This happens on port injection, too, but fuel system cleaners and gas detergents can clean the intake valves in port injection.
 
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