Synthetic oils and my take on them in our cars.

Pete · 16th December 2004, 00:03

What are the advantages of synthetics over petro based oils?

1. greater thermal stability, less thermal breakdown
2. greater detergency or cleaning ability
3. can flow at very low temperatures
4. higher vaporization temperature
5. less shearing under temperature and load

Thermal stability is important to long life of the lubricant. Additives and the base stock used are primary determiners of a lubricants thermal stability. Even if you see your oil temp guage show some normal reading it's important to know that in the engine there are much hotter areas for the oil to contend with than where the temp probe is located. Within the bearings, temperatures can approach 300 degrees F., and at the rings perhaps 500+ degrees. Petro based oil breakdown at these temps is assured.

Detergency is important to help sweep the combustion contaminants from the engine interior into the oil filter. Higher detergency prevents any buildup of these contaminants on the steel surfaces in the oil channels, and oil flow areas. Keeping these areas clear is important since any buildups can break free to contaminate smaller passages in the engine. This is probably why some people assert it's not a good idea to run a synthetic after using a petro based oil since the synthetics detergency is so great it might wash out prior contaminant deposits and foul the passages.

Low flow capability is an obvious advantage. Oil gets to where it needs to go qiucker during cold start conditions or in very cold weather. Synthetics can flow down to perhaps -40 F. Petro based oils with their parrafin wax dont do nearly as well in this regard.

Petro based oils have a tendency to vaporize off at high temperatures, which of course results in the deposits of contaminants that were in the oil prior to vaporization. These contaminant particles now have the ability to adhere to the interior surfaces of the engine.

Viscosity is everything in an engine. Petro based oils, once subject to high temperatures and high stress will thin out from the heat , and shear under increasing loads in the bearings. The hydrodynamic oil film in the sleeve bearing area of the mains is compromised. It will thin out, and the internal bearing oil pressure will be less. If there is a lesser thickness oil film in the bearing it will be able to handle lesser and lesser loads before metal to metal contact is made, and the soft main bearing material undermined. In a mains type sleeve bearing there is a very interesting oil flow shape, a resevoir of oil if you will, within the clearance of the bearing journal and bore. As best as I can describe it, it is a teardrop shape, and the oil is dragged off this teardrop by the crank journal into the high pressure region where the max load is. if this thin film boundary lube point is undermined, the engine is toast. Oil that is no longer up to carrying its rated load will not be able to prevent that metal to metal contact.

How hard are you on your oil? Not an easy question since not much is readily available to give you clear indicators how your driving style or trip lngths affect lubricants. Generally , if you dont let the oil and engine temps stabilize during a drive, thats hard on a lube. Trips over 10 miles should get you to those temps, trips under 10 miles or so, are rather hard on lubricants. Usually , on those short trips, combustion moisture and acids are not dealt with effectively by burning them off, nor have the piston rings fully temped up and seated. We all know what happens when the rings arent doing an effective job of sealing on an 11.5:1 compression engine.

Contrast the car that get 12,000 miles a year of highway trips of 30-150 miles duration with another car that gets 12,000 miles a year of 10 mile jaunts, easy to see now.

How about when you start the car? Do you let it get to temp befor you drive first, or do you take off within 30-60 seconds. Give yourself a star if you drive off within 30-60 seconds and dont let it idle for a long time. Idling a car to awrm her up takes far too long to get to operating temperature and is also very hard on the oil for the prior reasons also. Get that car moving, and keep the revs down low until shes all warmed up.

Now to get to the meat of the matter and see whats what with those Group IV and V synthetic lubricants.

group IV:

IN a nutshell their manufactured from Polyalphaolefins, which are made from synthesizing hydrocarbons. They offer most but not all the benefits of a true synthetic. They lack in a true synthetics increased detergency and thermal stability, so they get some additive packages to to up thier performance in these areas. I do not refer to group IV based lubricants as true synthetics since they are still hydrocarbon based, even though man made. In this group , the additives usually give the different characteristics and performance differences in this group of lubricants. Amsoil and Mobil 1 are the two best known of the Group IV base stock lubricants. generally speaking, these oils will be appropriate for most peoples driving styles, and they should be changed at no greater intervals than perhaps 5000-6000 miles.

group V:

These are the true synthetics made from organic esters, not containing hydrocarbons at all. They have all the benefits listed at the top of this thread in abundance.

These oils usually do not require any additives, and that is the main reason they have such extended change intervals. Most oils need to be changed due to thier additive packs being depleted.

These oils are also very expensive, but a conservative change interval of 10,000 miles evens out the cost a bit. Some of us , myself included, change them out at 7500 miles just for the feel good factor.

By the way, even though you dont change the oil for extended miles, dont be confused , still change the filter at 3000 miles maximum. The synthetics deal with engine sludges and contaminants better than petro based oils, they do not prevent them from forming though, so you still have to filter them out.

I believe the best known brand name for this group is Redline.

The castrol we get from the BMW dealer is a Group IV based lubricant.

The Castrol Syntec you can buy at the local NAPPA ia Group III based oil.

group I - III based oils are just not applicable to our engines, forget about them.

schnelleM5 · 16th December 2004, 04:06

Thank you for taking the time to share your knowledge, Pete. I suppose then that Castrol TWS 10w-60 would be classified as a Group IV lubricant? Which Group V oil do you run in "The Precious"?

Thanks.

ELEVENS · 16th December 2004, 04:26

Thanks Pete. I'm guessing that the "BMW High Performance Synthetic" oil belongs to Group IV?

jaj · 16th December 2004, 07:12

Gents

According to the Swiss Castrol website, Castrol TWS Motorsport 10w-60 is a "full synthetic", meaning a either Grp IV or Grp V, and most likely a blend of the two. This stuff is not LL01 or LL98 rated, but it is the oil that BMW Motorsport uses in the Formula BMW engines and in the M3 GTR V8.

Informed opinion on this site and others is that Castrol High Performance Synthetic Oil 5w-30 is actually the same product as Castrol TXT Softec LL01, which is also "synthetic". TXT is probably a Grp IV base oil, presumably with a whale of an additive package so you can run it for 30,000KM, per the LL01 spec. A Grp III base oil fulfils LL98, but a sythetic base is REQUIRED for LL01.

In North America, a great oil available from the retail chain stores is German-made Castrol Syntec 0w-30, a Grp IV/Grp V blend that carries the LL01 rating as well. It appears to be the same as Castrol Formula SLX in Europe. It's the "thinner, long-life" version of TWS, and I understand that Audi uses it for racing.

Cheers
JJ

Pete · 16th December 2004, 08:10

SchnelleM5,

Precious right now is running with Redline SAE 10W40 , a true synthetic with a polyol ester base stock. It meets API service class SL/SJ/SH/CD/CF.

The website for redline oil is redlineoil.com and has some very good reading to more fully investigate and understand the whole business about synthetics. You will probably feel very comfortable in alternate synthetic lubricant selections after reading and understanding the info on this web site.

Elevens,

Yes the BMW Synthetic is a Group IV base stock lubricant, with a synthetic hydrocarbon base stock.

jaj,

I was unaware that Castrol returned to using a synthetic base stock for Syntec oils. I do know that in 1997 they went from a group IV base stock to a Group III base stock. Thats about the same time they ran afoul of some advertising claims that were a bit suspect. I seem to remember some discussion about the oils Sodium Hydroxide additive problems. Seems that they could not get the long life of a true synthetic since the Sodium Hydroxide depleted long before the extemded mileage oil changes could be reached, causing some acid problems. I'll check this out as my memory might be misleading me here, but thats what I recall.
If its true that they have gone back to Group IV base stocks thats refreshing news indeed. Or were you refering exclusively to the 0W-30 lubricant?

Pete · 16th December 2004, 16:39

I found some more information about Syntec.

It appears that indeed Syntec was altered in 1997 to a Group III base stock oil from a Group IV. However, thru some ruling by the NARC (national advertising review council), Castrol has been allowed to market this oil as a synthetic. NARC based its decision on the process of Syntecs refining, it appears to undergo further refining than regular petro oils.

The problem with Syntec was in fact its inability to support long drain intervals. The reason for this was the sodium hydroxide issue as previously mentioned.

The ruling by he NARC did cause Mobil to file objections with them with respect to some advertising claims made by castrol which were technically inaccurate. Mobil was not a happy camper about all of this.

I also went on castrols website and could not find any statement as to what they use for a base stock for this lubricant. They do however advertise it as a synthetic. From the available data sheets on that site it meets most if not all the requirments of auto manufacturers, however I did not see any claims about drain intervals. Just dont expect to get the life from syntec that you would from say redline or mobil 1.

If anyone has more detailed info I would appreciate your input.

By the way, the further refining process syntec goes through is something clled hydroisomerization. Does anyone know what the heck that process is?

jaj · 16th December 2004, 17:12

Pete

From what I can see in researching motor oil, lubrication engineers use Viscosity Index as a proxy for purity in base oils (not finished products). Hence, low VI oils are around 100 and are "Grp I". High VI oils are higher group numbers, and Grp III and Grp IV have similar ranges of VI - but Grp IV is made by isomerizing ethylene gas, and Grp III is made by isomerizing petroleum crude oil. Grp IV contains the least amount of imperfections, and hence is the most resistant to oxidation and sludge formation. Of course, that's the base - toss in an additive package with a Grp I carrier oil, and all that purity is for nought!

In North America, Grp III can be called "synthetic" and there are some excellent oils based on it, like Castrol Syntec. The biggest difference for actual use is that Grp IV-based oils will last longer than Grp III. The differences are not dramatic (BMW in the LL98 spec allows Grp III for 25,000 KM use, while LL01 requires a full synthetic base and allows its use for 30,000 KM).

Then there's the odd man out -- German-made Syntec 0w-30 (and there is also a North American made Syntec 0w-30 out there) appears to be repackaged European Formula SLX, which is referred to as "Vollsynthese", or "Full Synthetic" in Germany. The only oils that Castrol makes that they call Vollsynthese are SLX, Formula RS, and TWS. The rest are "highly processed petroleum oils", or Grp III. SLX passes BMW LL01, so it's the real deal. So does Mobil 1 0w-40 by the way - but it's the only Mobil product that meets LL-anything!

Cheers
JJ

Philip · 16th December 2004, 17:30

Hello Pete,

Thanks for the information. BMW recommends an oil change at least once a year. Since I put about 2K on the M5 per year, what is happening to the oil to require a change? I'm assuming that this doesn't happen if the oil is kept in its sealed container. What's the shelf life of it?

Thanks for the education, Philip

MAH · 16th December 2004, 20:20

Pete,

Good discussion here. Let me try and understand what the implications are from your dicussion above.

Are the oils that BMW reccommends, ie. Castrol 5W-30 synthetic good for 7500 mile oil change intervals or 5000 mile changes?

Thanks,

Mark

Pete · 16th December 2004, 20:53

MAH
Since the oil BMW recommends is the Group IV synthetic it should be fine to use it for 7500 miles. If your driving conditioins are more severe than what might be considered normal it would be a good idea to maybe change the filter a bit more frequently. I would still change the Group IV oils at 5000 mile intervals, but thats just me. I change the filter at 2500 mile intervals.

Philip
I have no idea why BMW recommends to change the oil once a year, other than to say , at least you get the car in for a look see once a year. On the other hand, synthetics are not invincible. BMW probably assumes a certain amount of starts take place in a years time. If the trips are short, thats hard even on the synthetics, so best to err on the side of caution and just have it replaced once a year even if you dont put any miles on the car. I can envision also that they might have some concern about water condensation issues over a years time, but thats just speculation.

jaj
I am constantly amazed at how many different ways the car industry has to describe or quantify the quality and selection of oils. Its much easier in the world of industrial lubricants.
I thought I'd give this Redline 10W-40 a try now that its it colder here and see if I can tell any differences. It's kind of hard to determine any gains so far, not even sure if there will be any. Mileage still seems to be the same so probably not going to be able to quanitify anything noticable.
One thing I did notice, and I"m not sure if its a fluke or what, but I have had it in now for 1000 miles and I havent noticed very much oil consumption yet. I found that rather odd, and cannot come to a reasonable explanation for it as yet. Maybe that will change with a bit more spirited driving.

We will see.