What's the definitive word on synth oil and heat

[rdupre@houston.rr.com]

I don't want to start an oil religious war here. I know that there are strong adherents on each side. I just have a problem to solve and changing the type of oil may provide a solution...

Recently I read in a couple of places recommending not to use synthetic oil in an air cooled engine. Evidently, the oil is formulated to not break down under heat, rather than to remove engine heat as needed in the type IV engine we all know and love.

My car's PO ran synthetic oil and I've continued with Mobil One. And yes it leaks a little but not enough to be too much a bother. This isn't a problem I'm trying to solve. Heat is!

My car has always had a heat problem. I've done everything short of installing an aftermarket oil cooler and it still runs around 240-250. When it hits the 260 mark, I stop for a few minutes and let it cool off.

So I was thinking about going back to a high quality fossil oil and seeing if this would keep the car at a better operating temperature.

I understand that you should pick an oil and stay with it. Changing from non-detergent to detergent types can cause problems (or is it the other way around?) Can going from synthetic to fossil also cause problems.

I've been reading the comments on this board and most of them center around synthetic oil causing more leaks, but little has been said about the thermal properties. It seems to me that if synth oil doesn't break down as much under heat, yet itself causes the heat, it's a Phyrric victory. Perhaps running fossil oil won't cause the overheating, so the extra heat dynamics of synthetic oil may not be needed.

So, my question to the group is this.
1. What is the real story on synthetic oils in air cooled engines
2. Is it safe or wise to go back to fossil oil, if so, what type, weight, detergent/non detergent, etc?

[maf 914]

If you're talking Type IV, you might want to go to the Type4rum at Shop Talk Forums and do a search for synthetic oil. The consensus seems to be that aircooled engines actually run cooler with it, both oil and head temperature. I've used it but I don't have the proper gauges to tell any difference. I do think it leaks more though, you don't need a gauge for that! LOL!

Mike

[campbellcj]

I have actually never heard of, or noticed a difference in conduction properties between dino and synthetic.

The BIG reason a lot of folks run synth oil is that is doesn't break down quite as easily/soon under high temps. That is especially important in forced-induction cars, and air/oil-cooled cars IMHO.

Let your oil cooler get rid of the heat... but whatever heat it can't get rid of, you want your oil to be able to withstand.

Is your car stock, more or less? If so, are you hitting 250-260 on the street or on the track? If street, that is pretty darn hot. You may want to (re)check your engine mounted cooler, to make sure it's not crudded up, and check for major airflow leaks or obstructions i.e. engine tin and seals.

[rdupre@houston.rr.com]

Mike,

I just popped over to the the Shop Talk Forums. It looks like there might be a goodly amount of information there, if you could search for it. Seems that their search engine is down and has been for a few days.

It is interesting that you say that the consensus there is that synthetic oil runs the engine cooler. This is just opposite of what VW Trends says in this months issue.

The gist of what they are saying is that synthetic oils were designed for water cooled engines where the water preforms the cooling and the oil the lubricating. The oil is not designed to absorb and remove the heat. I checked around and Harley Davidson also gives this opinion.

So you can see where I get confused. Differnt people, different opinions, 180 degrees opposite.

And ChrisC,

I've done all the recommended things to check out the oil temperature problems, checked the tin, set the timing, cleaned the oil cooler, checked the air disrupters under the car and countless other things. That's why I'm grasping at this straw.

[AaronM]

Personally, even if synthetic doesn't conduct the heat as well, I'd be much more concerned about thermal breakdown. Even if synthetic does run a little hotter, it's less likely to coke with high heat and end up sludging oil passages. That's just my layman's opinion though.

Aaron

[Zeke]

I believe the Porsche factory has been putting Mobil 1 in their cars from at least the 993 (air cooled) days. Your other question about switching between detergent and non-detergent oil...I don't believe that it is any great harm to actually switch either way. However, why would there ever be any non-detergent oil in your motor? Non-detergent oil is for lawnmowers and air compressors and I'm not so sure about the lawnmower.

[John Rogers]

In my race car we use 20-50 regular oil on the first startup after an engine assembly and when the oil is at 200 degrees the idle pressure is about 7 psi. After we put the mobile 1 5-50 in the idle pressure is about 15 psi. Running pressure at 5000 RPM is about the same for each. I do know for a fact that synthetic oil is a hell of a lot slicker when you run through it on a race track!

[Mark Henry]

Originally posted by Zeke
switching between detergent and non-detergent oil...I don't believe that it is any great harm to actually switch either way. However, why would there ever be any non-detergent oil in your motor? Non-detergent oil is for lawnmowers and air compressors and I'm not so sure about the lawnmower.

Zeke, VW put non-detergent 20w oil in the aircooled engines for break-in, and a lot of old-timers still do this.

I beleive it is not good to switch back to non-detergent, can't remember why.

[campbellcj]

I've heard of the non-detergent philosophy for initial break-in too. Don't know the science behind it, but I think generally that oil is replaced somewhere between 20 minutes and a couple of days.

I have also heard the theory that you should not run synth in a brand new engine, until you are sure the rings are seated and all the parts are comfy cozy with each other. Again, as Milt says, this sounds like bunk because a lot of new cars (Porsches being one of them) come factory filled with Mobil1.

I ran switched my last 914 to Mobil1 at unknown mileage and had no new leak issues. The current car is actually running straight 50W Valvoline Racing dino juice at the moment. When the six is installed, it will run synth oil for sure.

Ron - I noticed you're in Houston. The temp & humidity there sure won't help your operating temps. Still sounds really hot for a stock motor though...are you confident in your temp gauge & sender? My big-four (carbed 2.4 w/ headers etc) only sees about 230 tops on the street, with no external cooler yet. It is about to get a huge cooler up front though, cuz it really cooks on the track. Hits 250-260 very rapidly when you run 5000+ rpm's for any extended period of time.

[hardflex]

I have a mechanical "water temp" guage hooked up to my 72, and my oil temp dropped from 240 to 220 at highway speed when I switched to Mobil 1 some years ago, which I would attribute to lower friction, As in less wear, too. And that temp is measured in the sump, what must it be point zero at the crank bearings or piston rings? I like the extra margin at high temp's that synthetic's give, plus they flow better at low temps.

you don't say what kind of engine you have, but this time of year (it's not always hot and humid in Houston) you shouldn't be seeing that kind of heating. Are you sure your mixtures and timing are correct? You haven't sucked a rag into the fan have you? Cooling system function properly?

[Dave at Pelican Parts]

I have read of one set of tests ("quench tests") that showed that one particular synthetic oil (an old formulation of Mobil-1, perhaps?) was better than several conventional oils at sucking the heat out of hot metal.

I don't know of any reason not to switch back to mineral oil, at least in the short term.

If an engine has run non-detergent oil for a while, it is not good to switch to detergent oil. This is because the non-detergent will have left crap all over the inside of the motor, but usually in out-of-the-way places. Switching to detergent oil will tend to loosen all that crap up, sending it through the rest of the oiling system where it may block an oil passage and cause problems.

Of course, this hasn't been a problem in a couple of decades, because it is pretty tough to get automotive motor oils that are non-detergent nowadays.

If you want to switch back to non-synthetic oil to see what happens to the oil temps, go for it. I'd be surprised to see much difference, though.

--DD

[Zeke]

Originally posted by Mark Henry
Zeke, VW put non-detergent 20w oil in the aircooled engines for break-in, and a lot of old-timers still do this.

I have heard this as well, but he didn't say anything about break-in. He wanted to know about oils in general for general driving. For that, I'll stick to my answer, that non-detergent oil is for air compressors. I broke my engine in with detergent oil. It's going out after 30 min and before I start it again. It will have Valveoline racing oil in it. But then, I don't drive on the street, unless it's the Streets of Willow.

[sammyg2]

Synthetic oil is slipperier is that a word?) and reduces friction a little thus reducing slightly the amount of heat generated. Most of that is because of the more expensive and higher quality additives in the top of the line oil. Probably not enough to notice. It's also thinner.
As far as heat convection, probably not much difference.

Synthetic will withstand higher temperatures before breaking down.

Synthetic oil can cause more leaks on an older car, but not for the reasons everyone thinks. It is much thinner than conventional oils so it can get out through smaller holes. The branch chain molecules are physically smaller, but not by much. Also the aforementioned additive package can help it to flow better, adding to possible leaks. They also clean sludge and carbon from the inside of the engine and can open previously clogged leak paths.
My 911 engine did not leak a drop of oil until I switched to shell synthetic, then it started leaking a small amount onto the HEs. It has tapered off to almost nothing now.

Here's some more trivia about sythetic oil:
It is basically identical to refined motor oil, but is more specific. Regular motor oil, as is almost everything in organic chemistry, is made up of a mixture of many different hydrocarbon compounds. In the refining and distillation process the desired "range" of molecules is maximized and the undesireable "ranges" of molecules are reduced as much as is physically and economically possible. There is still bad stuff in there, but the amount is acceptable. This bad stuff are impurities that speed up the breakdown of the oil.
Synthetic oil takes the distillation process to a new level. The desired range of molecules are catalytically farmed to maximize the good stuff and almost eliminate the bad stuff. So, it is not really different than dino oil, it is just super-refined.
Oh, and the detergent packages are higher quality also. I think I mentioned that

[DSPTurtle]

Here's one for you guys... I ahve read that if you use Mobil 1 in your air compressor, it will actually work better. There was one company (Cambell I think) that actually required Mobil 1 if you were going to run the compressor "continuously". I was afraid of it sneaking by the rings and getting into the air stream but so far I have had no problems (knock on wood). It does seem like it is making more horsepower though when I rev it up to 8000 rpm... just kidding But I do run Mobil 1 10w30 in my new compressor.

[red-beard]

Primary reason for not using Synthetic during break in:

$$$$$$$

You want to keep changing the oil as long as you keep seeing the silver shimmer in the oil. Cheap dino oil is the way to go until the engine is broken in. Synthetic cost a lot per change.

2nd reason not to use Synthetic in your tranny just after rebuild...if ya gotta go back in, you're going to have to drain it. You're better off using dino for the first 1 or 2 changes, until you are sure the engine or tranny is now working perfectly and not leaking.

James

[bernbomb914]

Back in the old days (mid 70's IMSA) when super vees ran type 4 engines Bunce Enginering found that when they went to syn. oil they went from 3hrs. to 9 hrs. before they split the cases. They turned 8 to 9 g's and developed 160 hp with 1600 cc. very hard life but they held up.

[norustscott]

The reason not to use synthetic during break in is that it works too well. I think we all agree that Synthetic has superior protection against wear caused by friction. During a break in you need friction...Rings to cylinders, lifters to cam lobes are the two main frinction points that are addressed during the critical first 30 mins or so of engine life. Rings need to be seated and the cam needs to be( for lack of a better word) Tempered. I run mobile one in the H2O vanagon with great success. I do have single hyfro lifter that leaks down if it sits for more than a couple of days. I feel it is the synthetic oil and its extreme viscosity variances. It flows very well when cold. It pumps back up after a minute.

I would love to run synthetic in the Fourteen. I do wonder about the claims that the synthetic oil does not ransfer heat as well as Petrol based. An old friend and VW technician from the aircooled era sold me on Kendall straight 30w. I think it is the GT-1 line. 20 years without an oil related problem...Now has anyone heard of a product called MilliTech...It is an oil additive that has millitary approval. I can't remember the chemical compound but I am sure it is the same stuff as Dura Lube and others. This stuff is supposed to bond to metal surfaces making them slicker....Nice claim. Not sure if I buy it. Thoughts? 914 application?

[red-beard]

I'm running Synthetic in the 6 right now in both the tranny and the engine. I've only owned the 6 a year....so I can't give a long term run on this.

I did run Mobil 1 in my Honda Accord for 230,000 miles. No engine breakdown issues that I know of. The main observable difference I noticed was that oil varnish never formed under the valve cover or on the head.

James

[cnavarro]

I'd hop onto vwvortex.com (mind you I know that it is not a porsche site) and go into the technical -> 1.8t forum. Oil is a very important choice in these forced induction motors, and to conquer the speculation and heresay about synthetics (and even between different brands of synthetics), many members have taken to doing Oil analysis of their motor oils at every service interval. Great reading.

We've personally tested lots of different synthetics, each having its own subtle differences: torco, royal purple, mobil 1, castrol, delvac 1, and the list goes on and on. For best bang vs buck, we've found Mobil's Delvac 1 5w40 Full synthetic excellent, and we've split the case a few times since starting to run Delvac and there is no visible wear on any of the "wear" surfaces. Some would argue that a diesel oil is not good for a gas engine, but Delvac carries all the APIs required for both gas and diesel service, and exceeds many more stringent requirements needed for forced induction applications. They also claim a 100,000 mile drain interval...but that is a different story altogether, considering we don't have bypass oil filters that filter down to less than a micron. :-)

We can usually get Delvac 1 at our local Farm and Fleet for 19.99/gal. Not too bad...

I'm currently testing Royal Purple's Racing 41 (7w40) in my 1.8T and I am planning on doing an oil analysis to substantiate RP's claims that their sythetic is the best. Till then, the debate continues on....

Take care,

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[Dave at Pelican Parts]

I wouldn't use the milivac additive--or any oil additive, for that matter. If you pick a good oil, it will have all the additives that it needs already in it, and adding more on top of that is just a waste of money. Plus, some additives can have "synergistic" effects, where something completely out of proportion happens when you add the wrong two things together.

--DD