Pennzoil 5W-20, '04 Mazda RX-8, 2000 miles

[molechaser]

This is my third sample on my RX-8. Overall it appears that wear metals from break-in are trending down nicely.

This interval was a bit different from the previous two in that I took it for a 400 mile trip just before changing the oil. I did a double oil change last time so very little of the factory fill should remain at this point. Also, this sample was taken with a Vampire pump (excellent!).

Results are listed from most recent to oldest, and Blackstone did all the tests.

code:

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Oil Pennzoil Pennzoil Mazda

Grade 5W-20 5W-20 5W-20

Miles on Oil 2014 1967 2037

Miles on Car 6018 4004 2037

Time on Oil, days 77 97 102

Make-up Oil, qt 0.7 1.0 0.0

Oil Filter OEM OEM OEM

Air Filter OEM OEM OEM

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Al 3 6 9

Cr 3 5 5

Fe 16 30 30

Cu 4 13 19

Pb 2 1 3

Sn 0 0 2

Mo 240 289 551

Ni 0 0 0

Mn 0 1 1

Ag 0 0 0

Ti 0 0 0

K 0 6 9

B 79 84 130

Si 7 21 49

Na 2 4 8

Ca 2110 1845 1750

Mg 4 5 4

P 768 641 745

Zn 937 718 817

Ba 0 0 1

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SUS @210°F 48.5 46.9 48.7

Flashpoint,°F 355 310 335

Fuel, % 1.5 2.3 1.5

Antifreeze, % 0 0 0

Water, % 0 TR 0

Insolubles TR 0.4 0.2

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Viscosity continues to run on the low side due to the ongoing fuel dilution. This may improve as the engine continues to break in, but this time around, I re-filled with Castrol Syntec Blend 10W-30.

This was the last of my short interval changes. I plan to sample again 2000 miles into the next interval using the Vampire and depending on the results stretch it out to 4000 miles.

 

[STSinNYC]

Your results look pretty good. Curious why you changed to the Castrol 10W-30?

 

[molechaser]

The main reason for the switch to 10W-30 was to see if a thicker oil will make any difference in the wear numbers. Because the engine is still breaking in it may be hard to tell.

Viscosity has been low on every sample. This is partly due to the fuel dilution but shearing may also be a factor in this engine because of the gears between the rotors and end housings.

I don't have any complaint about how the Pennzoil has performed and only switched to Castrol because the Syntec Blend is readily available and hopefully will prove to be as well built as the Pennzoil 5W-20.

 

[Al]

You need to get that fuel dilution under control-pronto its taking your 20 wt oil clost to a 10 wt. that's why your irons are so high (probably).

 

[metroplex]

How do you know its a fuel dilution problem? Do any of the other RX8s have the same amount of fuel in there?

Do you drive in the city mostly or on the highway?

Try to change your driving habits to allow the engine to reach operating temperatures.

 

[TR3-2001SE]

This RX8 engines are designed to run rich. I would think 1.5 is fairly normal for this engine. It protects the cat converter is my understanding because these engines run hotter than normal so the fuel cools the cat. Of course we have not seem many after lots of milage to see ifthe fuel dulition comes down with time.
This looks to be an excellent report for this engine as the wear metals are all trending down as it breaks in.

[ May 13, 2004, 12:01 PM: Message edited by: TR3-2001SE ]

 

[Schmoe]

I had the earlier editions of the rotary engines back in the 80's. Just loved the 13B engine. I was running a straight 40 weight oil and it seemed to help the oil burning. But everybody I knew that had one, they all burned oil. The nature of the apex seals and by engine design. These things spin a lot harder than a piston engine. Can see that Pennz. is starting to lower their ZDP amounts already and cranking up the moly. Nice little package for a dino. Not a lot you can do about fuel dilution on a rotary. Some of the gases are going to leak through from compression into the planetary gears where the oil is at.

 

[TR3-2001SE]

I owned a 1979 RX7 for two years and in that time no oil was consumed. My favorite oil at the time was Castrol GTX and I probably used the 20w-50. Hope I didn't mess up the engine with this higher weight oil. It has done well for me over 30 years in Mercedes Diesels as well as several sports cars.

 

[Al]

quote:

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Originally posted by TR3-2001SE:
I would think 1.5 is fairly normal for this engine.

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Well-I would not be happy with it. Look at the flashpoints, and the viscosity degredation and the wear. That sounds just like the answers that Ford (and others) give when their vehicles are screwed up. So it may be "normal" but it is not good. (for the engine and the oil). Also note the consupmtion. They solved one problem only to create another. Happens all the time in Engineering

 

[Quick_lude]

The design/nature of the rotary engine coupled with fuel rich ecu programming is causing the fuel dilution. The rotary engine is not thermally efficient and takes a long time to reach operating temperature vs a piston engine. This exacerbates the problem. Mazda is also very adamant about recommending a 5w20 oil, no idea why though since the low weight combined with fuel dilution brings it close to a 10w level.

Personally I would use at least a 10w30.

 

[molechaser]

Al - the oil consumption is normal and expected since this engine has a metering pump that injects oil through four nozzles directly into the engine. This is required to lube the apex seals at the rotor tips.

With this engine, I would only be concerned if there wasn't any oil consumption.

 

[molechaser]

I believe TR3 is right about the engine running rich by design. Compaddict has posted UOA's that also show fuel dilution.

There are aftermarket black boxes that lean out the PCM fuel maps, but I'm staying stock. Mazda has issued a flash for the PCM that may help some and I should be getting that in the near future.

The fuel dilution does not appear to be causing any harm and the trial of 30 weight oil should give me some idea of whether the viscosity is too low when I'm running 5W-20.