yrotory

I changed my oil for the second time at 4000 miles and sent a sample off for analysis again.

During this interval weather was on the cool side during most of February and I had the dreaded milky mung on the dipstick (the car's..not mine ).

Following is the readers digest summary of the results with the most recent numbers listed first. Both intervals were about 2000 miles.

Oil......Pennzoil.....OEM
..........5W-20........5W-20

Aluminum....6.......9
Chromium...5.......5
Iron............30.....30
Copper.......13.....19
Lead...........1.......3
Tin..............0........2
Silicon.........21......49

Viscosity, SUS @ 210°F.....46.9.....48.7....(Should be 52-61)
Flashpoint, °F....................310......335.....(Should be > 355)
Fuel, %..............................2.3.......1.5...... (Should be < 2.0)
Water, %.........................trace......0........(Sho uld be < 0.1)

Wear metals are generally trending down as expected as the car breaks in. Iron and chrome may be slow to fall considering the construction of this engine.

The lab is concerned about the fuel dilution, and the resulting viscosity is borderline 10 weight oil. Virgin Pennzoil 5W-20 should be 54 SUS @ 210°F based on info from the Pennzoil website. I refilled again with Pennzoil 5W-20 but did a double change after letting the oil run a few days. If the fuel dilution continues, I am going to switch to 30 weight oil.

The lab noted the trace water present and speculated that I had drained the oil cold. They weren't concerned about the trace water. In reality, I drained the oil after a 50 mile highway run so it was plenty hot. For those finding emulsion when they check the oil level, it looks like this is a nuisance and not a problem.

yrotory

Gyro

In other words, if the lab had found a significant amount of water in the oil, the emulsion would represent a real problem, correct?

Since the lab only noticed a trace amount, it is of no real concern. OK.

You have also noticed foamy oil on the dipstick? EDIT...I re-read your post and saw that you did have the foamy dipstick

RX8_GT

I assume the normal value / acceptable level are for piston engines ?

John

yrotory

John...the normal values for viscosity and flashpoint should hold for any engine. They are just properties of the oil.

That said, fuel dilution will lower the viscosity and flashpoint so if fuel dilution is "normal" for the rotary engine then low viscosity and flashpoint are sure to follow.

Most of my mileage is short trips of less than 10 miles and during the three months on the last oil interval weather was cool, so this probably contributes to the high fuel dilution I am seeing. Also, the seals may not yet be fully seated.

I'm just not comfortable with the reported viscosity at this point although the rest of the analysis looked fine for a new engine. Barring some improvement in the fuel dilution/viscosity I will be switching to a heavier oil to compensate.

yrotory

RX8_GT

Yrotory

Seems a reasonable move - that is to a 5W30 oil. I believe most of the rest of the world use 5W30 at Mazda's request.

John

Gord96BRG

Thanks for posting those analysis results. I'd agree about the viscosity concerns - I actually use 5W30 for my home oil changes (every 4K km between the dealer's 8K km changes), I'll let the dealer use 5W20 for theirs! It's nice to see break-in data also.

Regards,
Gordon

RX8_GT

Please keep the forum informed - not many of other have such data available.

John

Rotarian_SC

Yeah, i also used Penzoil 5W-20. Now i can kinda smell gasoline in my oil, which i could not smell with the stock oil. It might just b that the car is older now or the oil, can't tell. I am having it taken into the dealer soon anyway.

rxeightr

Good stuff. You have helped me decide to use 5W-30 for future oil changes.

Rx8Freehk

Thats what I use, 5W-30 but I use Mobil 1, I said screw it ... synthetic till I die!!!!

Rotarian_SC

I think that if the oil that mazda gives us doesn't sufficiently protect the engine then mazda would have to give us something like a new 8. However I see that if we use synthetic or 5W-30 that we would be liable for any problem that came up due to oil.

Gord96BRG

How on earth do you see liability for using a synthetic 5W20? All Mazda specifies is viscosity (5W20) and rating (API SL). Mazda's own specification make absolutely NO mention of synthetic or dino oil. Use of 5W20 API SL synthetic oil is completely warranty compliant, with absolutely no problems or liability possible legally.

Regards,
Gordon

Nubo

Seeing as how the engine is spec'd for 5w30 in other markets I think Mazda would have an awfully weak case claiming "abuse" if you use it. There is convincing argument that 5w20 is being spec'd mainly for CAFE purposes. Another corroborating bit of evidence are the number of members who've reported that some Mazda dealerships themselves are filling with 5w30 oil unless one of us finicky RX-8 owners calls them on it.

Given the known issue of the engine running overly rich, fuel dilution is a worry and yrotary's oil analysis falls in line. I've been waffling on which oil to use during the 3 months I've been reading the forums and waiting for the car. But I have finally made up my mind to go with 5w30 Mobil1 synthetic.

Rotarian_SC

Actually in my drivers manual it specifically mentions not to use synthetic oil...

But I do understand using 5W-30 if mazda is using it in foreign markets and some places in the US.

Gord96BRG

I'm not going to say you're wrong, because there is a slight possibility that Mazda revised the owner's manual since mine was printed... Would you mind checking again, and telling us the exact page number of the owner's manual where Mazda specifically mentions not to use synthetic oil, and could you give us the exact quote? I'm very curious, because this is the very first mention from anyone that claims Mazda specifically forbids synthetic in the owner's manual. (Actually, it's not, it's just that any prior claims like this have resulted in people coming back after checking and saying "oops, I was mistaken" :D )

Regards,
Gordon

Rotarian_SC

Well i was kinda wrong. It wasn't actually printed in my drivers manual but my dealer put a slip of paper in there at then between 8-8 and 8-9 that mentions not to use synthetic oil. Though i could have sworn that i saw it in official print somewhere, maybe on a sticker under the hood. Will check that in the morning.

BlueThunder

OK Then. 5W30 it is. However seens we need to add oil often in the RX8(like a quart every 1000 miles+ or - what's the sence to use the synthentic instead the normal?

Rotarian_SC

i have added only a quart and i have gone 3k miles. I have checked my dipstick every week to make sure. I ran out of the quart i was adding so my oil is only halfway full right now. I need to buy some more.

Gord96BRG

The benefits of synthetic oil are unrelated to how much is used, they're the same for any engine. Much better lubrication at startup (and 80% of engine wear occurs in the first 30 seconds after a cold start, so that benefit is critical), much better resistance to thermal breakdown at high heat, much better shear resistance under high stress/load, much better flow characteristics at very low temperatures (not just cold starts, but COLD starts like at -20 degrees!), and more.

Even if you have to add a liter every 1000 miles or so - the extended life capability of synthetic oil comes into play because of the oil change characteristics. RX-8 oil capacity is around 7.4 litres, yet an oil change only gets 3.7 liters, or about half the capacity. So each oil change, you're leaving half the old oil behind - I prefer that to be the more capable synthetic oil!

Regards,
Gordon

Rotarian_SC

Well after looking on my car the only source I have is the dealer slip in my manual, but I could have sworn I saw it in official writing somewhere.