Official "What oil / additives should I use" topic

[udidwht]

[Jimmy111]

Rick.
Your 77 type 4 was stuffed full of smog equipment from the factory and had oil temps is the 260-280F range. so it ran very hot. In that motor if you had the smog equipment installed I would use 20-50. But if no smog equipment I would use 5-30. The absolute minimum any motor either water or air cooled should run at is 180F. 180F is concidered severe duty by all auto manufactures and requires more frequent oil changes. Any less than that will cause ring wear and other problems. Optimum oil temp should be a minimum of 212 but 225 is better to evaporate the condensation from the oil. Most VW guys target the 212F because the extra heat can kill the engine..

The guy that said he has 180 on his new truck is FOS or he has a problem. Almost all new cars are designed for a 50F minimum higher oil temp than water temp. The rest are designed with a 75F differential.

On every combustion stroke the gasoline is turned into water vapor and you get a small amount of it into your engine oil on every stroke due to blowby. IF the oil temp does not exceed 212 your oil will turn into a white stickey mess which many people mention has happened to them. This emulsion of oil and water does nothing to lubricate your motor.

Mag cased VW's have the problem that AS-41 starts to weaken at 240F and becomes Jello at 300F. So if you have a Mag cased VW if is best to keep the oil temp as close to 212 as possible and select your oil to meet that temp. this is the main reason for using SAE 30 series oils

If you have an aluminum cased VW you can have max temps that exceed 300F and not have any structural problems.

Many people point out that Aircooled Aircraft engines use SAE 50 series oils and run in the 180 -225 degree temp range so their VW should use the same because it is basicly the same design. But they never take into acount the much larger bearing clearances in a Lycoming engine compared to a VW engine. The clearance is almost 75% larger in a Lycoming than in a VW motor. This is the reason for the higher viscosity.

[merlinj79]

[Jimmy111]

All type 4 cases are Aluminum. Very good heat treated aluminum too.
Up to 1975 all type 1 were As-41 Magnesium, 1975 and later were AS-21.
The cooling of the oil is based on speed of flow (quantity) thru the oil cooler. A lower viscosity will flow more oil thru the oil cooler and less oil out the pressure control valve. So you will get cooler oil.

[Max Welton]

I'm slowly talking myself into a larger pump and thinner oil setup. I've been running 30mm pumps with Berg pressure relief covers and 10w30 for years. The cover caps things at a little over 40 psi on this engine. And pressure at 220º is just about right.

So last oil change I switched to 5w30. I still have plenty of pressure when the oil is cold, so now I'm looking for a 0w30.

Max
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[bugninva]

[udidwht]

[Bruce]

[Jimmy111]

Yes, the water will evaporate at 180F but it will take 30-45 minutes for it to do so at 180F. Most people dont drive their car for that long.

There are mountains of techincal papers and indepth testing that have been written and done on the subject of minimum and maximum oil temperatures. So much that no one seems to want to do it anymore.
The SAE technical papers on The Effect of Oil Rheology on Journal Bearing Performance and cylinder bore wear of An Operating Engine clearly state that a absolute minimum oil temperture of 180F should be maintained for many reasons including evaporation of condensation.

[miniman82]

[gregthomas]

[udidwht]

Anyone like to take a guess at how long it would take before damage like this would occur? On a vehicle that's driven regularly and receives oil changes at normal intervals.

[miniman82]

Doesn't matter how long it takes, fact is it happens. And it doesn't matter how ofter the vehicle is driven, it's HOW LONG. If you drive regularly for 10 minutes each day to work, you're not driving long enough.
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[Jimmy111]

I dont think that with todays oils a whole lot of Acid is generated. But Im not really sure. Havent studdied it in a while.
In the past with Dino oils which we used without purifying, they contained a lot of sulfide metals like zinc sulphide, lead sulfide and molybdeum sulfide among others. We liked these metals in the oil because they helped with shear in the oil. But when emissions came out and Cat converters were invented these metals poisoned them and had to be removed. The sulfide metals would decompose into metilic oxides and sulfuric acid when heated and in contact with water.

But magnesium and water with a little acid added to it creates a very good battery. So with just a little water and Acid you will get a lot of corrosion of your case. Many people have this problem when water collects in the sump next to the screen and corrodes away the area where the screen bolts on to.

[ap_sand]

After the success of Mobil 1 in the automotive world, Mobil pursued certification of a full synthetic aviation oil. Extensive testing in high usage environments (i.e. training, charter, and cargo) showed significant advances in reducing wear.

After it received full approval by the FAA and was deployed with great fanfare to the entire piston GA fleet, problems started coming up. Turned out that synthetics don’t “hold” the acids that form when there is insufficient usage to significantly boil out the generated moisture and let them precipitate out. It ate up both plain (plane… ha!) bearings along with the yellow metals in the accessory drive section. Cost Mobil tens of millions in replacement costs and the oil was pulled from the market.

It was quite a while until Shell came out with a synthetic formulation for aircraft and even that is a partial synthetic blend.

The rule of thumb is that an hour of FLIGHT is needed to purge the accumulated moisture from the oil. If you can’t fly it, don’t just go to the airport and ground run it to “circulate the oil”. It’s PROVEN to do more harm than good and is documented in the manufacturers ops manuals.

[bluebug79]

which oils have significant zddp content nowadays?

[Glenn]

[miniman82]

[Wilfredo R]

I was told by my local vw shop that you use 10w-30/40 in the winter and 20w-50 in the summer, is that what you guys use?

[Fattie]

if one isn't going to read this entire thread....and just pops in here with a question... this thread will continue to repete itself.... example.. the above question

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