As an Engineer I sometimes start to dig for information on topics I am interested in...like Dino vs. Synthetics.

It is true that Synth has longer chain molecules, but that's just one side of it. Synth has more uniform long chain molecules. Dino has both long and short chain molecules. It is the short chains that will volitize and burn up first when stressed, which in turn leads to acid formations and more oil breakdown. So given the same circumstances the Dino will break down faster than synth.

So then, what situations break down oil? the number one thing is TURBO's. The oil cooling and lubricating the turbo is subject to extreme heat and stresses much greater than any other place in an engine. Since we don't have turbos, that leaves most of us out.

Aside from that though, the superior viscocity control and additive stability really do improve the lubrication ability of the synthetics as opposed to the dino.

My conclusion is that 928 motors do not NEED synthetics to run fine. But in my opinion the benefits from running them far out weigh the costs of purchase. Increased lubrication, lowered wear, lowered heat buildup, etc. Personally, I run only synthetic lubricants in all my cars.

As far as changing the oil, I don't go more than 5,000 miles on my Turbo motors or 10,000 on my non turbo's. BUT I do change my oil filters at 5,000 miles. (That's a topic all it's own.) If I don't get to the mileage in less than a year then I change the oil after it's been one year. Condensation, contamination and age still come into play.

OK...I feel better now <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

 

I saw this previous post and thought I could add something to it.
I joined a racing club for a little while (then I moved - long story) Anyway, the first meeting I went to had a chap from a racing team there to give us a long lecture on dino vs. synthetic oil. Most of what has been said in this thread makes sense. There was one GIANT word of caution from this fellow about synthetic. He said that they had just torn down a $75,000 racing engine for the second time thanks to synthetic oil!!!!!
The reason for this was the fact that after they built this hipo 911, they stored it for about 9-10 months, for whatever reason. When they went back in to the engine after the semi-long storage, everything inside the motor had pitted and there was even some rust formation. The reason that was given was that the synthetic oil was so fluid, it ran completely off all of the internal parts of the engine and allowed mother nature to do her worst. I'm not kidding!!!! This guy claimed that the engine was all but ruined. He said that synthetic has a lot of really positive attributes but people who store their cars for long periods of time should stay away from it at all costs. He said the dino oil has much better clinging qualities against the metal surfaces and does a much better job at protecting the engine internals against corrosion.
My advice would be that if you drive your 928 fairly regularly, synthetic is fine - but if you store the car for months at a time (Northern Folk) stay away from synthetic and let the dino oil do its thing.
My shark had synthetic in it when I bought it and it leaked like crazy. Switched over to dino and the leaks are down to one small drip, drip, drip

<img src="graemlins/wave.gif" border="0" alt="[byebye]" />

 

I use Mobil-1 in my car and it gets stored a good part of the year. After 5+ months of storage, I removed the valve covers to change my cam timing. There was still a coating of the Mobil-1 on everything in there.

 

I have changed from dino oil to synethetic oil because of other reasons than high temperature redlines at the track and frequent use of the car, but because of an article I read from Devek.net. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />

OIL DRIVEN DETONATION.

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Here's the article:
Oil driven detonation: The 928's chronic oil lifting behavior at higher rpms dumps oil into the induction system, causes smoke in the exhaust and, detonation of the engine at its peak output. That's because oil mixing with the injected fuel lowers the effective octane rating and hence the detonation threshold. Detonation damages pistons, valves, and rings, and forces rebuilds before the 928's 200,000+ mile engine life has been attained. Some racers use two-cycle engine oil in the crankcase because that oil is formulated to be burned and is specially blended to be compatible with fuel.

The Fix: Install DEVEK's oil control modifications at the next engine disassembly. AT THE NEXT OIL CHANGE, fill with Red Line or Valvoline synthetic oils. Porsche tested a broad range of oils for fuel compatibility and found Valvoline synthetics to reduce detonation when mixed with fuel and burned in an internal combustion engine. The Red Line synthetic oils are blended for compatibility with the higher octane fuels recommended for Porsche engines.
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Now, my wallet tells me no on the Devek oil control modifications, but yes to Valvoline Full Synthetic. I have noticed more oil loss with the Valvoline synthetic as to the Valvoline dino, but if 928s really have bad oil lifting behaviors and synthetic offers more protection, then why not?

I fill with 10w-30 in the winter and 20w-50 in the summer. Oil changes every 5000 miles for me.

Andrew
'84 928S
<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

i went from m1 15-50 to castrol dino 20-50 for the following reasons: to lessen risk of seal and oil pan leakage, and $15 a case vs $60 a case. this is a preference issue but on an older car my thought is to minimize risks of leaks. one really doesn't want to "save" the engine internals only to have to pull the rear end and torque tube to replace a $10 rear seal. i've sworn off m1 in this car and am here to spread the word.

 

I use Redline synthetic in the engine mostly because of the detonation issue, plus I have always liked synthetics. The only spot on my garage floor is from the oil cooler line sealing rings at the block. Next oil change, I'll replace the sealing rings. There is some wetness on the engine from the rear cam seals, but nothing settles in the garage floor.

I have not had to add oil since I put the redline in almost 2,000 miles ago. Not bad for a 119K engine running synthetic.

BTW, I understand that synthetic does not cause leaks, it just gets past marginal seals where dino oil may not. So, if you put synthetic in and leaks develop, you can always switch back to dino or a blend and some of those leaks may go away. There is some thought that switching back and forth is not a good idea, but there are mixed opinions on that one. If I switched back, I would go to a blend for a while first, change the filter more frequently, then if needed go to straight dino. There are also some internal cleansing methods using detergent oils, atf and a short drive, etc. IMO, I would not use motor flush of any kind. I would change the filter often if changing oil types.

My 2 cents
Greg

 

I have a lot of experience with synthetics and wanted to add my 2 cents.

Firstly, the only bad experience I had with synthetic was in an RX7. The engine was so tired that the new synthetic I put in filled the cylinders so it wouldn't even run. Rotary engines have a really wild set of seals to seal the cylinder not as simple as piston rings. All these "wipers" can leak really easily. Bad mistake on an old rotary.

Everything else has been great so far. I had an old 240z that I ran and ran on synthetic. My brother still has it. I have no way of knowing just how many miles is on it but it is a lot. Hardly ever changed it also.

Next was an old Ford Bronco that I bought. After I put in synthetic in the gear train (differentials, tranney, transfer case) I went for a test drive and felt that something was funny. I quickly realized that it was the absence of gear noise. Significantly quieter. There were some drips from the 30+ year old seals. Not too bad though.

Next was a Honda Civic that I bought new. I broke it in with conventional oil then ran synthetic. I only changed the oil and filter every summer (about 30,000 miles between changes). The oil would be clean and about 1/2 quart low. I sold the car with 160k miles on it and it was still only about 1/2 quart low at each 30,000 mile oil change. Ran great when I sold it, and the oil was still clean.

Now clean oil isn't all that it's cracked up to be. I believe that oil should have a lot of detergent in it. This will make the oil black in an older engine until it is entirely clean. On my 928, the manual tranny was shifting terrible when I bought it. I drained the gear oil and it was crystal clear. To most, a good sign. To me, maybe not, no detergent to clean the synchros! I put in Amsoil racing gear oil and noticed immediate improvements. Actually, amazing improvements.

I also put Amsoil into the engine and have noticed no leaks or adverse effects.

We change our oil because it gets

1: dirty
2: breaks down
3: impurities such as water, etc

If you believe the preceeding, then you must also believe that if you can eliminate the above 3 then you ELIMINATE THE NEED TO CHANGE YOUR OIL!!!!!!!!!

If you run a synthetic that resists viscosity break down you have eliminated number 2.

What about 1 & 3. Check out Amsoils Bypass system. The filters filter down to the 1 micron range whereas the usual filter only goes down to around 20 or so. It also removes water. check out this link for an overview: <a href="http://www.amsoil.com/lit/g52.pdf" target="_blank">http://www.amsoil.com/lit/g52.pdf</a>

Additionally, I don't recall reading in the above discussion about the higher "coking" point of synthetics. Coking is when the oil burns and forms carbon particles. These are essentially black diamonds that abrade your engine. Synthetics don't coke until much higher temperatures. (remember that syntex commercial with the frying pan?)

Amsoil was the first in synthetics and I have been very impressed with their product. When discussions of the additional price come up regarding synthetics, they aren't applicable because of the extended intervals of oil change (or no oil change).

I've heard rumors of big rigs going over a million miles with Amsoil bypass systems installed before needing to be rebuilt. I can't verify, but several such rumors exist. I can only tell you what I've seen on my cars.

Amsoil also has a program where you can send in small samples of your oil for diagnosis on a regular basis to put your mind at ease.

One big problem with the bypass system (I have it on 2 of my 4 cars so far), I can't find anywhere to fit it on my 928!!! It is going to be a challenge to fit it.

I have recently talked with a shop that does oil changes here in California. The restrictions for disposing of the oil are getting worse and worse. It could be soon that all vehicles will be required to have a bypass system such as the one by Amsoil. I also hear that Mercedes is using sensors to monitor oil and tells the driver when it becomes unacceptable and needs changing. Rumor is that these cars may go beyond the 20k miles mark before needing a change.

hope it helps

 

I too will support the ideas for synthetic oils. I have a supercharged 560 SEC Mercedes as well as the 928. Before I switched to synthetic oil the car would detonate very badly in hot weather, but now I'm not having any detonation problems even with the Florida 100+ degree temps. I noticed detonation with Mobile 1 so I tried Valvoline Syntec and have not experienced any detonation.

Jim Nowak