It's an interesting piece, but I'd be careful how much stake you put on the basis of a test of one particular car, with spectrographic analysis of a particular sample's metal content becoming the only measurement of wear on an engine's internals.

 

im using the same Mobil 1 as you are... but recently i tried the new supersynth...

weird that the Mobil1 site only recommends 5W-30 and 10W-30...?? i remember it last time they state that we can use 15W-50... but i can be mistaken...

 

I recently just changed to 15W50 Mobil 1 (From 20W50 RP) for winter time use. Seems to work just fine.....

-Dan

 

Why are we still having this oil debate. A new post like this shows up once every month or so. It has been debated to death and then some. Please people, can we move on?

 

I've been using 20w50 year round... but I don't usually drive it in the winter anyway.... I change every 2000 miles (and the oil is really dark by then).

 

Yeah really, next time a newb question happens again, a mod should just close it down with one reply directing them to all the links.... Then again that probably has been done before already so as long as there are newbs there will be questions like these............

 

I've found this thread quite interesting. Thanks to the guys who posted the links. This is new info to me.

7racer, I'm going on 4000 miles with the M1 15W50, topped off with 1 qt of 10W30 M1. It's been cold here in Indy, and I'm not up to changing the oil until spring, and planned on changing the filter only...ironically it seems top-off oil and frequent filter changes might be enough according to your link?! With ~$5/qt for M1, and the fact that our 13B REWs burn 1 US qt/1000-miles--requiring a top-off with a new qt of oil every 1000-miles--lends credence to the data found in your link http://neptune.spacebears.com/cars/stories/mobil1.html 15000 mile oil change intervals with four oil filter changes every 3000 miles, and 1 quart-per-thousand miles top-offs might actually work--hell you might never have to change the oil at all with rotaries , so long as you're using full synthetics, and changing the oil filter 4 times per year

 

The dark color is from the carbon. Not sure the filter will remove that...FWIW, I used to change my oil between track events, usually with only 500 miles between events. Even with so few miles, the oil is dark from all the on-boost use during open-track

 

LOL!

yes...this does get debated but I was trying to add something new.

The "test" is interesting, but I wish they had a "control" set of data that is just normal dino oil.

kento is right about the data...but besides the Ford SAE paper that he quoted, it is the most scientific study that I have found. It is hard to quantify engine wear. Besides taking the engine apart every 5000 and measuring for engine wear, I thought their experiment was pretty good. I really can't think of how else you could do the measurements besides measuring the oil properties.

Yep Manny! Top it off Well at least it doesn't seem as far fetched as it did before.

However, anyone want to enlighten me on how FREQUENT oil change (3000 miles) causes MORE engine wear?!? I still haven't reasoned that one out.

Also, you can see if you goto the home page that they are doing a comparison of Amsoil vs. Mobil1....if any rotorheads live around these guys, mind volunteering your car for some oil analysis???

 

That's what I was referring to when I questioned their reasoning and data to make such an assumption. Sure, making a spectrographic analysis of an oil's metal compounds gives you an accurate reading of those compounds (remember that certain metal compounds are already present in the oil) in that particular sample, but making the assumption that more frequent oil changes increase engine wear based strictly upon those readings is a bit of a stretch. Where and how did they obtain the oil samples from the engine? You can't just drop some oil out of the sump and proclaim "OK, we've got an accurate reading here!" (remember that certain compounds-- as well as contaminants-- don't remain "perfectly suspended" and distributed throughout the oil in the engine) This may also explain their varying TBN-- as well as metal compound, and possibly viscosity-- results from sample to sample.

Basically, it's extremely difficult to find an engine failure that can be blamed solely on oil breakdown. But like any other contributing factor to engine performance, most of us want the very best for our FDs (although many want the best "bang for the buck"), so we want the oil we use to perform at its best. Actually making that determination, however, depends on way too many factors (not the least of which is the differing opinions of "performance" between each individual) for anyone to actually say unequivocally that "changing your oil frequently is a waste."

It should also be noted that the rotary's oil supply gets "sheared" by the meshing gears of the eccentric shaft and rotor teeth, something that doesn't happen in conventional piston engines.

 

Could have sworn you don't ever use synthetic oil in a rotary engine since the engine is designed to burn oil and some synthetic oils don't burn clean and leave residue after they are burned. Just had this conversation with a lady that bought a new rx-8 dealership told her that synth oil would void warranty.

 

WHY ARE YOU GUYS TALKING ABOUT SYNTHETIC AND MOBILE ONE. YOU ACT AS IF YOU DONT OWN FD'S. YOU DONT USE SYNTHETICS ON THE FD'S MOTOR!!!

 

The key word there is "some". The majority of ester-based (Motul, Royal Purple) and highly refined PAO-based (Mobil 1, Amsoil) oils burn cleanly. Apparently Mazda still doesn't want to take the chance of someone using some Joe Blow brand oil and possibly sticking an apex seal.

 

Straight from the Racing Beat Rotary Performance Technical Manual:

"The Mazda factory does not recommend the use of synthetic oils in their rotary engines - specifically addressing this issue in the Owner's Manual.

In 1979, Racing Beat began testing synthetic lubrication products. Without a doubt, the best synthetic oils do perform well in extreme heat (over 300 F) and extreme cold (below 32 F), but by the nature of Mazda's rotary engine, the oil temperature never exceeds 250 F without severe engine damage due to other factors. In Souther California, we have difficulty seeing the low-temperature benefits: however, when we put synthetic lubricants in the engine, transmission, and differential in our IMSA GTU race car, we immediately saw what we later found to be a common result: The oil temperature in all three locations dropped 5 to 10 F for the same operating conditions. This is apparently due to two factors: reduced friction between sliding surfaces, and reduced foaming. As we continued to use synthetic oil products it became clear that they genuinely reduced wear. We also found benefits in street use. On two occassions, cars with "scratchy" transmissions synchronizers were completely cured by a change to synthetic gear lube. After many years of experience with these products we have observed only one problem: because of the reduced friction, the time necessary to break in an engine, transmission, or limted slip differential (standard differentials are no problem) is excessively long, so we recommend using mineral oil in all three for a time to ensure rapid break in."