Motorcraft 5W-20 SL, 2072 mi on oil, 04 Mazda Rx8

[OMCWankel]

Hello All! This is my first UOA post.

Motorcraft 5W-20 SL/GF-3
-2072 mi on oil, in service 3 months, sample date 5-1-05, sample during oil change (hot)
-11,008 total miles on vehicle, 2004 Mazda RX8, 1.3L Rotary, 4 spd AT
-4 qt oil at change, capacity is 7 quarts, 0.5 qt added during interval
-4 oz Lube Control added at oil change, 1 oz added 1000 mi into interval
-Shell V-power gasoline, 4 oz TC-W3 added per 8 gal, 1 oz Fuel Power added per 8 gal
-Mazda OEM oil filter
-K&N Filtercharger air filter
-Spirited driving, occasional redlines, 70% highway, 30% city, 10-60 min/day in traffic jams, temperatures ranging from low 40 F to high 80 F
-Lab is Blackstone

Element UOA#1
Aluminum 1
Chromium 4
Iron 23
Copper 10
Lead 2
Tin 0
Molybdenum 36
Nickel 0
Manganese 0
Silver 0
Titanium 0
Potassium 0
Boron 2
Silicon 4
Sodium 2
Calcium 1520
Magnesium 6
Phosphorus 579
Zinc 718
Barium 0

Properties UOA#1
SUS @ 210F 51.6
Flashpoint 345
Fuel 1.3%
Antifreeze 0.0
Water 0.0
Insolubles 0.1

I am pleased with this report. Iron and Copper are a little high, but this motor is still breaking in. Silicone is good, indicating that I installed the K&N correctly (a tricky job on this car unless you remove the air box completely). Mileage is consistently 20 mpg, rising to 22 mpg highway only. Could fuel dilution be tied to the use of TC-W3/FP? I have the latest flash on the ECU.

 

[OMCWankel]

Sorry, forgot the TBN = 3.1

 

[JHZR2]

the engine ight be breaking in, but doesnt a wenkel have less specific frictional surfaces than a standard engine? Isnt the sump pretty big? All in all, considering breakin, Id say its a good report.

Did this engine come with syn frm the factory?

Why use so much fuel additive? 1oz FP per 8 gals fuel seems to work well in my applications. Ive never noted any real improvement in MPG in any of my vehices, and for routine cleaning, I doubt you need to use both additives. Id say to just go with FP (since it has been noted that it doest effect UOA results), at 1oz/8 gals fuel, and save your $$$

JMH

 

[OMCWankel]

JHZR2,
The rotary has 24 total side seals, and 6 total tip seals (2 Rotor). Only the innermost 12 side seals get sump lubrication. The other seals get lube from the oil injection system using sump oil. This is why the premix, to supliment the lubrication for the remaining 12 side seals and the 6 tip seals.

The factory fill appears to be dino 5W-20 with boatloads of moly and boron. Mazda still refuses to recommend synthetic oil for the rotary.

Colloquial evidence in older rotaries suggest supplimental premix oil in the gas equates to longer seal life in the rotary. I have not seen any scientific testing to prove or disprove this theory. My own personal test is not the best either, having two variables in the fuel instead of just one!

 

[y_p_w]

quote:

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Originally posted by OMCWankel:
JHZR2,
The rotary has 24 total side seals, and 6 total tip seals (2 Rotor). Only the innermost 12 side seals get sump lubrication. The other seals get lube from the oil injection system using sump oil. This is why the premix, to supliment the lubrication for the remaining 12 side seals and the 6 tip seals.

The factory fill appears to be dino 5W-20 with boatloads of moly and boron. Mazda still refuses to recommend synthetic oil for the rotary.

Colloquial evidence in older rotaries suggest supplimental premix oil in the gas equates to longer seal life in the rotary. I have not seen any scientific testing to prove or disprove this theory. My own personal test is not the best either, having two variables in the fuel instead of just one!

---

I've heard allegations that a PAO/ester mix just doesn't mix well with the fuel and those seals eventually dried up as a result.

 

[OMCWankel]

y_p_w,

Is your reference about PAO/Ester mix with fuel relative to the crankcase oil, or the pre-mix oil?

 

[Last_Z]

Correct me if I'm wrong, please. This engine used 3qts of oil in only 2k miles?

Is it designed to burn that much oil? Is the oil being burned through this pre-mix system you speak of? I don't know what to make of this report. I think I would use something a little thicker for better compression seal. Fuel is very high, especially for mostly highway miles.

 

[AndyH]

quote:

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Originally posted by Last_Z:
Correct me if I'm wrong, please. This engine used 3qts of oil in only 2k miles?

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I believe (but I could be mistaken) that during a "normal" oil change on a rotary engine a certain amount of oil remains in the engine (3 quarts, from the look of it). I seem to recall another rotary engine UOA thread where this was discussed. I think it's possible to drain all the oil, but a royal pain in the neck to do so.

 

[TR3-2001SE]

I think the three quarts in in the oil cooler. This is an excellent report for a RX-8. In fact I think it is the best we have seen to date. I would stick with this oil.

 

[Last_Z]

quote:

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Originally posted by AndyH:

quote:

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Originally posted by Last_Z:
Correct me if I'm wrong, please. This engine used 3qts of oil in only 2k miles?

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I believe (but I could be mistaken) that during a "normal" oil change on a rotary engine a certain amount of oil remains in the engine (3 quarts, from the look of it). I seem to recall another rotary engine UOA thread where this was discussed. I think it's possible to drain all the oil, but a royal pain in the neck to do so.

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What is the point of this? Don't make a whole lot of sense. The only thing I can think of (if what you said is true) is that the remanining oil stays in some reservoir for the "pre-mix"

 

[OMCWankel]

Last_Z,

Crankcase oil in the rotary is used for three things: Main shaft/stationary gear lube, injection into the combustion chamber to lube the seals, and internal cooling of the two rotors. Oil is left inside the rotors, and in the oil cooler lines and cooler, when you do a conventional oil change. Almost no oil is left in the injection pump, as it has no reservoir, instead injecting directly off the oil gallery.

Total oil capacity of the system is about 7 quarts. Only about 4 to 4.5 quarts are drained and re-filled at an OCI. That is why most rotary OCI's are at 2000-3000 mi. You will get most of the old oil out after 3-4 changes.

Because of this system, part of the oil in the rotary is subjected to extended OCI of 10,000 to 12,000 mi, like it or not

 

[Last_Z]

I'm tempted to criticize this engine........but I won't. The oil thing sure is weird though. Let's just say the main advantages they have is simplicity and high RPM potential.

Have dyno tested yet?

 

[OMCWankel]

Last_Z,
Go ahead and criticize, you can't be tougher on it than the folks at the RX8Club forum

No one is a fan of the "partial oil change", and no one has found a way around it yet. Several folks have suggested dropping the oil cooler lines, but there is still a lot of oil in the rotors.

No dyno on my part, I have the AT version with a 7500 rpm redline, making 200 hp at the crank. Butt dyno says no real power until 5000, but she do crank it on after that

TR3-2001SE,
Thanks for the positive comments

SpacerX is also using this oil and posting. I think his analysis shows even better iron, copper and fuel dilution than mine

 

[Jay]

quote:

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Originally posted by OMCWankel:
JHZR2,
...Colloquial evidence in older rotaries suggest supplimental premix oil in the gas equates to longer seal life in the rotary. I have not seen any scientific testing to prove or disprove this theory. My own personal test is not the best either, having two variables in the fuel instead of just one!

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Maybe you could test this premix theory a little more rigorously and put the question to rest.