http://www.google.com.au/search?hl=e...G=Search&meta=
TBN:In a motor oil, this is a property which allows the oil to neutralize acids from combustion that would otherwise degrade the oil.

 

Aaah, that makes sense then. That's obviously why Mobil 1 lasts longer than other oils ... I remember working it out as being somehting like 15000kms before it starts to break down vs. GTX3 which lasts about 7500kms in my old MX6 ...

... definately pays to spend more on oil eh?

 

WOW you guys know so much about this stuff......

I just buy it...put in car.....burn it....top it up and change it........

There is something strange about knowing soooo much...not that I am knocking it... but really there is a limit......

IMHO: when using a synthetic oil, which I did for 10,000kms...there was a marked decrease in the amount of oil the car consumed. Dropping back to mineral oil there is an increase in how much it uses....

Does it really make much difference seeing as the stuff is in the car for 5-10,oookms it;s hardly long enough for it to get too dirty...

God forbid the condition of the engine oil in some of the cars on the road.....

 

I think your observed difference in consumption between synth and mineral is evidence of the reason why people (Mazda as well) tend to want you to use mineral. Oil is injected into the combustion chamber of all rotaries to lubricate the apex seals. It needs to burn off cleanly. The amount should simply vary with your driving style, not with the type of oil. (Ooops, that little statement should be good for 6 pages of follow-on posts )

 

TBN stands for Total Base Number, and is the result of a chemical analysis. My company's instrumentation can do TBN analyses. It is a measure of the amount of acid neutralizing compounds added to the oil, which have an alkaline (or "basic") character. It could also be that the TBN rating of Mobil 1 is higher than the Valvoline because the Mobil 1 is more prone to breakdown than the Valvoline, and the manufacturer needs to compensate for that.

Another parameter that is important is TAN, Total Acid Number, which measures those acidic substances which aren't neutralized (it can happen - don't get me started on acid-base theory). When I was adapting this analysis to our instrumentation, I tried it out on some very old oil (it was quite black) taken from a clapped out bomb driven by one of my colleagues. The TAN was only slightly higher than brand new oil. This suggests that the oil additives were still doing their job, although I'm sure that the lubricating properties were crap.

Thank you, Cromax, for the link to the bobistheoilguy website. I really learned a lot. I would recommend it to all forum members, even those who haven't a technical background. It is written in an easy to understand manner, and should help to dispense with some of the myths and legends that abound with oils.

There is a clue in the section on additives (at the bottom of "Lubrication Design") why it might be wise to use the Mazda rotary oil only. You can see that there is a special additive designed to swell elastomeric seals. This might be fine in conventional motors, but given the critical role of elastomeric seals in rotary motors, it is just possible that this might be left out in formulating the Mazda oil.

 

long story short labrat, tell me which bottle to buy. :p

 

Mazda rotary oil from your local friendly Mazda dealer. Check and top up your oil every 1000km or 2 tankfulls. Change oil at 10000km service, unless you reckon its looking dark at 5000km.

 

2 tanks of petrol?

 

That's about 900km, just in case you forget to look at your odometer. I need something to remind me.

 

That's the safe route. Has anyone had the ability to get their hands on the data sheets for MRO though? I use two oils in my other cars (with otto cycle engines), a Motul 10W-40 Full Synthetic or Mobil 1 if I couldn't get the Motul, reason being that I actually used those for a practical exercise at uni and in comparison with other oils they came up best. In the RX8 I also put about 200mL of Motul 800 2T in the petrol tank after speaking to a mate of mine who's a chemical engineer.

I've actually been thinking about modifying the OMP as I'm not very happy with dirty sump oil being thrown into the clean combustion chamber.

 

Don’t do that .Just put some premix two stroke synthetic oil in the fuel tank on fill up .That’s what I do and most people who own rotary work shops

Lubricates the whole fuel system and puts fresh oil in the combustion chamber

Idiot proof, and if your engine could talk it’d say ……..ahhhhhhhhhhhhh thanx mate

 

Agree with the premix comments. I only premix on track days. I normally add 100mls in each full tank.

 

I guess ... that's what I'm doing at the moment, it runs a lot smoother and doesn't sound as harsh with a tid bit of oil in the tank.