Mineral Oil vs. Synthetic

[bill shurvinton]

Iwan,

Would you care to back those statements up with some factual data. Like what died on the FC at how many miles and what constituent of the oil base stock caused this problem?

[bill shurvinton]

Thought I\'d do some research. Sad but true. Mainly because the oil topic is so badly understood and oft misquoted \'my mates brothers etc\'.

So. Starting with the internals.

Synthetics offer:
    Better cleaning
    Less foaming (which means lower oil temps 10 degrees is mentioned by racing beat IIRC)
    Better shear resistance
    Better high temperature properties
    Less polymeric breakdown
    Less friction (possibly 5HP or more in rotary. I intend to test this theory).

And I think everyone is happy with this.

Now we come to the burning. My research has thrown up that the problem is with the detergent package. These clean the engine, but leave \'ash\' when they burn. the more detergent the worse this is. Now there are readily available tables on the web, but not much in terms of this ash content for the leading synthetics. But for a dino oil example Castrol GTX is 0.85% residue when burned. Redline make a big fuss about putting very little detergent in, but I have yet to find a %ash figure. Full race oils (usually monograde) generally have no detergent in, as they are not intended for extended interval running. The only residue figure for a synthetic I found was 0.5%.

So the upshot is that most engine oils will not burn completely cleaning, dino or synthetic. If you want the best for your rotary then it would seem that premixing 2 stroke, which is guaranteed to burn with no residue is the only way. Dirty oil is guranteed to kill things. I have a couple of dead engines which had thick layers of crud in the inlet manifolds and a crust on the rotors. These certainly never saw synthetic, and as far as I can tell, very few oil changes at all.

More research now needed.

Bill

[racer1]

If Mazda that manufactures these cars says ONLY MINERAL then i will stick to this because they must have their reasons. Now anybody wants to use synthetics is welcome to do so. I use Apexi Mineral oil and make frequent changes every 1000km due to the high temps here in Cyprus and everything is working fine.

[iaint]

Originally posted by bill shurvinton
Thought I\'d do some research. Sad but true. Mainly because the oil topic is so badly understood and oft misquoted \'my mates brothers etc\'.

[snip]

More research now needed.

Bill

One other thing to think about it the fuel used too.  I think most of us seem to run optimax and Shell make some claims about the fuel\'s engine cleaning properties.

If the claims are to be believed then does this mean that they would offset the buildup caused by any oil used in the engine?

If the fuel contains detergents then what will this do to the oil around the seals>  Will it cause it to breakdown and be less viscous and increase friction and wear?

It could be that even though Optimax is good for the engine with it\'s higher octane rating that it\'s actually detrimental in other ways.  Not saying it of course but it\'s a possiblity.

The most important question would be how do we go about getting real data on this?  Who could carry out this research?  One would hope that Mazda have for the new Renesis engine and that it should be largely applicable to the 13b and others.

What kind of oil are Mazda saying to use with the RX-8?  Would thast mean that synth oils have moved on since the 7 was launched?

My guess is that we\'ll never know for sure as the research is unlikely to be released by mazda at any point soon.

Iain

[fd3s_rx7]

Originally posted by Fish
MINERAL ONLY!!!!!

Thats unless you run a premix setup, which I doubt you do.

Synthetic will foul up the seals.

Dan

What do you mean by premix setup???

How do you do it??

Thanks

[bill shurvinton]

Premix is where you add 2 stroke oil to the fuel, bypassing the OMP. Generally done when either

a) you run huge boost and need more oil than the OMP can deliver

b) You have a weber or ITB setup and can\'t use the stock oiling system

c) You think its hard to measure and pour fluids into the tank at a refill.


I don\'t have a turbo so I\'ll leave you guessing where I am.

Premixing should prolong engine life, but most premixed engines lead a very hard life.

Bill

[petemillis]

I know this is an old topic now but mention has been made re premixing. I run a 2 stroke enduro bike and have no choice but to premix. I can tell you with 100% certainty that synthetic premix oils do not burn completey and loads of spooge is produced even from 10 lites of fuel mixed at 50:1. However, the spooge is not ash - it is a slippery lubricating freely running black spooge that looks after things like the power valve mechanism and so on. I strip the engine down twice a year and there is NEVER any carbon deposit on the piston crown, the rings or on the combustion chamber. So I\'m guessing that a synth motor oil will be the same and will lubricate and be expelled with the exhaust rather then forming carbon?
Pete