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Nice. Those long oil change intervals of yours still creep me out. Interesting to me that Amsoil skated in just under the minimum viscosity spec. The sheer power of the rotary engine never ceases to amaze.
Nice. Those long oil change intervals of yours still creep me out. Interesting to me that Amsoil skated in just under the minimum viscosity spec. The sheer power of the rotary engine never ceases to amaze.
There I was thinking 6k was reasonably conservative Admittedly 4 track days and 6k might be pushing things, but it seems to work so I'm planning to stick to that interval for the next couple of changes and see how it goes.
I'm not worried about the viscosity at this point. It's likely the amsoil is that same viscosity when fresh, or at least close to fresh. (i.e. There might be some initial change, but it seems to be stable after that)
I've always had less than 0.5% fuel. Hopefully that 1.5% reading is just a one off and perhaps due to me moving the car from driveway to garage just before taking the sample.
Last edited by blu3dragon; 02-15-2016 at 10:25 AM.
This screen grab, (using Jing) may not be legible so I've also attached a .pdf version.
After buying this car new in December, 2007 I changed oil twice with Mobil 1 15W-50 - once at 1,000 miles and again at 3,600 miles. Since then, I have used Shell Rotella 5W-40 for every oil change, right around a 3,000 mile interval.
Because I have seen others on this forum running 6,000 miles between oil changes with generally good results, I decided to let the Rotella T6 go for 6k and see what a Blackstone analysis showed me. Except for the iron number I am satisfied with this OCI and this oil.
I had no make-up oil because this car uses the Sohn adapter, which I keep filled with a JASO FD oil.
Shell Rotella 10W30 is not for cars. Please use the Rotella T 15W40 non-synthetic. The Rotella 10W30 has very little Moly in it.
Shell Rotella T 15W40 non-synthetic diesel oil is great stuff for non-catalytic converter vehicles like motorcycles (and cat deleted rotaries). The issue in running Rotella 15W40 (non-synthetic) is that the higher levels of Zinc (as ZDDP) will improve wear but inactivate your catalyst sites in your catalytic converter much faster (what that leads to for buildup I haven't a clue). The sneaky US EPA made oil producers reduce the ZDDP levels in SM and SN rated oil to improve smog at the cost of your engine life and reliability (wear). I use Rotella T in my motorcycles just not in any of my cars for now while the cat is doing its job (no MIL lights for me).
My most recent oil analysis results on my S2: I use Super Tech 5W20 (SN rating) oil in the sump and JASO FD-rated synthetic premix (Lucas semi-synthetic FD) in the fuel. I run 0.25 oz/gal all the time and I've seen 1 oz/gal for tracking. I change my oil often ~ 1000 miles because I have the time and a quick drain valve to do it conveniently. 5W30 (SN rated) is fine since it's recommended by Mazda ex-US. I also use a N3R1 Mazda oil filter specific for the S2 every 3000 miles.
That Viscosity is really low for only 1000 miles. I typically see almost double that on mine after 3000 miles oil changes and I am boosted so my engine sees much higher loads.
I think you use 0W40 Mobil 1 correct? I'm using that "high Quality" SuperTech 5W20 oil from Wally World. Last time I read shear resistance testing data on bobistheoilguy Wally World's oil was on par with others.
I am also trying to keep my oil clean by trading higher frequent oil changes (for oil cleanliness) and lower cost oil. Since the S2 doesn't have easy off the shelf option that the S1 has in the SOHN adapter, this is my easy fix.
Look at some other reports, for example the liqui moly 10W40 above is still at 13.76 at 5000 miles. You can't compare directly due to many variables but if you did a full swap and ran a better oil I am guessing you would see far better results.
I am trying to balance wear and better oil cooling. Lower weight oils w/i the recommended range (so a 5W30, 0W40, and 5W20) will give better heat transfer rate for daily driving (I don't track my car yet). As mentioned above, I'm trying to turn the oil over more frequently to deliver cleaner oil through the OMP to the engine. A balance. Onc eI use up my 5W20 stock, I'll move to 5W30 conventional (SN grade).
Oil differences have no effect on cooling. I have been monitoring oil temps for years and have tried quite a few oils and there is no difference in oil temps between types and brands.
I am trying to balance wear and better oil cooling. Lower weight oils w/i the recommended range (so a 5W30, 0W40, and 5W20) will give better heat transfer rate for daily driving (I don't track my car yet). As mentioned above, I'm trying to turn the oil over more frequently to deliver cleaner oil through the OMP to the engine. A balance. Onc eI use up my 5W20 stock, I'll move to 5W30 conventional (SN grade).
You are actually right. thinner oils do protect bearing better than that of thicker oils. Most wear is on start up and you want a thinner oil. If a thinner oil can maintain good oil pressure (at temperature) the thinner oil is preferred as it protects and cools better than that of thicker oils.
The key with a lot of RX7 owners running high WHP is getting good cooling solutions for oil (25 row dual oil coolers). we mainly run 5W-30 oil in our 400-500WHP rotaries.
same thinking applies to RX8's.
Thinner is always better if you can maintain pressure. pressure is resistance to flow, it is illogical to think you can have the same flow with a really thick oil as the pressure is through the roof.
The rx7 group, those who test and think, all have gone from recommended oil to thick oil back to as think as we can run while maintaining pressure.
I will highlite some things form an SAE paper on motor oil.
Air in oil causes oxidation, wasted power, higher oil temperatures, loss of lubricity among other adverse effects. Higher RPM increases aeration, so does increasing oil viscosity. (‘Just FYI).
The rate of wear is much higher within 15-20 minutes of start-up than after reaching normal operating temperature. There was a lot of data but I conclude that the initial start-up time period (first 20 minutes) result is 100 nanometers of wear whereas the steady state wear rate was only 4 nanometers per hour thereafter. (Hence we should be concerned about start-up oil thickness more than running thickness. This justifies the statement that 95 percent of engine wear occurs just after start-up).
Oil aging, valve train and bearing problems and thermal problems occur with aeration. Below 110 C there is no problem but as one goes up the aeration ratio increases rapidly. (A cooler running engine from a thinner, faster flowing oil may lubricate better for this reason alone - aeration was a “hot” topic).
Viscosity data reveals that the more viscous oil did not significantly alter the cam angle of minimum oil film thickness. Of greater importance is the finding that the higher viscosity oil continued to exhibit boundary layer lubrication. (Ergo thicker is not necessarily better).
The effect of engine intake air humidity was significant so that tests are now done with specified humidity conditions.
It was postulated that fuel dilution of oil would elevate cam wear. Fuel dilution of 4.5 percent did not effect wear. (This would have the effect of lowering the viscosity about 1 grade).
By using lower viscosity oils there is less friction, improved cold weather starting, improved fuel economy, a savings of starting system components and less wear by increasing the rate of oil pressurization and flow in the upper oil galleries.
Other papers showed how they always consider older engines when formulating new oils for full backwards compatibility.
There was a lot on using thinner oils and how they do not result in excessive wear as previously feared. This is in part because of modern additives.
This stuff was very, very interesting. I will reiterate that you should use the latest, highest rated oil in your car regardless of it’s age. By definition all oils are backward compatible.
Use a grade thinner than you may at first think is best. Always use the oil with the lowest first number in the grade - use 0W-30 instead of 10W-30 and for many reasons use synthetic but mainly because of less wear and tear at start-up!
Viscosity and Wear
Thinner oils have less drag, and therefore less friction and wear...
Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.
(If your engine is 20 F cooler running a thinner oil then the viscosity is the same as the next higher weight grade. Also, as wear diminishes with lesser operating temperatures then we have a benefit. Another benefit is that the thinner oil is better at startup where the majority of wear occurs.)
The problem with theory is when it doesn't match reality. People always state that "thicker" oil raises oil pressures.
But I have been monitoring oil pressure and temps in the RX-8 for many years and from dealer supplied 5W-20 to 5W-40 diesel oil, I have never seen any differences in temps or pressures. Maybe if I lived where it got colder than 35F or so but I would but my cold start up pressure and operating temp pressures have been the same regardless of what oil I have run. Warm up times have never changed either.
Oh and this is thru multiple oil cooler setups using a proper oil thermostat.
02-14-2016, 06:57 PM
Admittedly 4 track days and 6k might be pushing things, but it seems to work so I'm planning to stick to that interval for the next couple of changes and see how it goes.
