Tech Article Title Author Date
More than you want to know about MOTOR OIL Jim TT 2000

There have been so many posts about oil I feel compelled to write about this subject a bit to share some of my thoughts in one shot (or two). Oils have many purposes in an internal combustion engine. In addition to lubricating they clean, dissipate and reduce heat in both moving and non-moving engine parts. There are many brands and types of oil on the market and while many of these lower cost over the counter brands are ok in many day to day situations there are better oils out there. In fact many oils do not measure up to their advertised claims such as "Low Sludge", "Mechanics Choice" or "Fights Thermal Breakdown".

As oil is circulated through your engine it dissipates heat stored in the parts it contacts, it also lubricates and removes friction from all moving parts which include: bearings, seals, cylinder walls, valve train, (lifters cam lobes etc). This we all know but oil does some things we don't normally think of. Oil is very important in aiding piston ring sealing; there is a small amount of oil that is burned off in this process. Unless of course your engine has poor piston ring "seating" in which case it burns more oil. Oil is also key in valve spring cooling as these parts reside in a very hot and enclosed area of the engine.

The oiling system of most motors is very simple and this is good. There is an oil pan that forms a reservoir, an oil pump which forces oil through a filter (typically 10 to 20 microns...which is not that great) then through the engines oil galleys which lead it to various bearing surfaces. Oil capacity can be as little as 3 quarts in a 500cc motorcycle to over 14 quarts in a big truck. Pumps are gear, chain or belt (toothed) driven and can be of internal or external design with multiple pump set-ups in some engines. Some high performance engine unitizes a dry sump where the oil is stored in a separate tank with a dedicated pump to pull oil from the tank and another to pump oil into the tank. The advantage of a dry sump is less friction or windage caused by the crankshaft plowing through oil and reduced heat but perhaps most important is a constant supply of oil. In some cases a wet sump can go dry if enough G force is exerted on the vehicle as in a racing application. A good example of this is a motorcycle doing a wheelie where all the oil runs to the back of the crankcase and away from the oil pick up. Airplanes also would have a similar problem flying upside-down, thus the dry sump. In fact, just braking hard enough in some vehicles is all it takes to cause a lack on oil at the pick up (often baffles are used in wet sump engines to prevent this). Inside the oil pump is a pressure spring or a loaded ball that mechanically controls oil pressure. Oil pressure varies with engine speed up to the maximum pressure allowed by this mechanical control. Believe it or not most oil pumps are not high volume pumps because if they were the sumps would quickly be sucked dry with all the oil ending up in the cylinder heads. Typically the more oil the system moves the more horsepower it takes to do so. Also of note is the fact that higher oil pressure causes a slight horse power drain. This is why in the AMA 600 Super Sport class (an essentially stock racing class) all the top teams use is very trick and hard to detect , lower than stock oil pressure system. This systems pressure is not low enough to cause an oiling failure but low enough to pick up a small power gain.

Along this line, the higher the oil viscosity, the more power it takes to pump the oil through the engine. Looking at racing again we see special synthetic 'zero weight' qualifying oil being used by Formula 1 teams (and Nascar) that our friends at Mobil have developed (I understand that certain F1 teams have their own formulations). Don't think this is going to extremes, not with one 800HP F1 engine completely used up in practice then thrown away. Well that's what a $330,000,000 budget will do (a top F1s teams annual budget).

Oil viscosity varies in a range for zero up to 90weight and beyond. There are 'straight weight' oils (straight 50 weight) and multi viscosity oils like 10W 40. In today's engines multi weight oils are the standard and there has been a trend towards lighter weight oils like 5w 30 where in the past 10w 40 was almost universal. Oils achieve this multi viscous nature by the use of long 'chain molecules' that unfold as they heat up. So they flow well at cold start up but don't thin to the point of film failure as temperatures rise. Oil temps as high as 275 degrees are normal and they can climb to 325 degrees at which point some oils begin to break down (synthetics are you best insurance against this). However there are flash points inside an engine were oil is subjected to extremely high temperature. Don't forget that combustion temp can reach 6000 degrees (hot enough to melt any metal in your engine- but that's another story). As we drive our oil begins to loose viscosity so a 10w 40 may become an 8w 30 over time. This happens by a process called 'shear down' where the long chain molecules are ground down into pieces. This is particularly troublesome in gearboxes, as meshing gear teeth are the prime crunchers of chain molecules. This is why motorcycles that use engine oil to lubricate their transmissions will never have the long oil change intervals we are seeing in autos. Automobile transmissions use separate oil for their gearboxes, typically something like straight 90weight-gear oil as an example. Many a home mechanic will wrongly assume that if 10w 40 is good 20w 50 is better for summer driving. This is not necessarily the case as heavier oil can reduce lubrication. This has to do with flow dynamics or lack there of in a heavier weight oil. All I'll say is follow the manufactures call out on the spec sheet.

As I said many times anyone that still believes that there is no benefit in using synthetic oils is simply uniformed. Good synthetic oils give you a horse power and mpg gain of between 1% and 3%. The lubricating qualities and slipperiness of synthetics are far superior to conventional oils and effectively extend engine life. Synthetics produce little or no residues and contaminants as compared to mineral-based oils. They have a much higher 'flash point' that allows them to dissipate heat better and lubricate better at extreme temperatures. They don't 'coke up' at high heat levels, which is good for a turbo charged car like the TT; think about the oil that lingers in the exhaust side of your turbo after shut off. These oils are also better in cold weather conditions due to their high flow characteristics at low temps (10% better than mineral based oils). A good analogy is to think of mineral based oils as an army made up of the general population; some solders are tall, some fat, some weak and some strong. In a synthetic oil army all solders are six feet tall and all are strong, an army of clones if you will. Just because you buy synthetic oil does not mean you have a 'good' synthetic. The good synthetics will give you up to a 3% increase in power (on a dyno pull) with a similar increase in gas mileage. My favorite synthetics are the Mobil 1 family of oils because they are readily available and because Mobil invented the stuff (I use 5W 30 but am looking at 0w 30). Back in the early 1960s the Navy asked Mobil to develop a lubricant that would not solidify. The problem was that their new carrier jets wheel-bearing grease was freezing solid at high altitude and upon landing the bearings would fail. Mobil came up with synthetic lubricants as the solution and the rest is history. Other good synthetic oil choices are Redline, Torco and Amsoil, the rest don't measure up on the dyno (no power increase).

There is a lot of debate over the oil change interval, which is now up to 15,000 on some maintenance schedules. First there is no argument that a synthetic oil can run longer between oil changes. But how long do you keep a synthetic in your engine, there is no simple answer but if you ask me I'll tell you 6000miles. While letting your oil go too long can do serious damage, you can't hurt your motor by changing oil frequently; you could change it every day with no ill effect. Regardless of how often you change oil you should check its level and top it off every week or with each fill up. The condition of an engine will bear on when you change oil as a motor that burns some oil will also have 'blow buy' and you will need to get these combustion contaminants out of the system. I have a collection of service manuals that go back as far as the 1940s and the 2000 to 3000 mile change interval was the norm then; oil, like motor technology has come a long way. This at least proves that Jiffy Lube is not responsible for the 3000-mile figure. This is all for now, I still want to write about break-in oils (this is an amazingly complex subject), oil additives and changing your oil at home.

OIL PART TWO, how is it made, what's in it and break-in issues

In today's word the technical aspects of life are such that they seem beyond the reach of the average person. How many times have you heard "you can't work on today's cars, they are too technical"(I don't agree with this)? There was a time in more agrarian societies when women and men knew just about everything technology wise. This is no longer the case but that doesn't mean we can't learn a lot, we don't need to sell ourselves short here. I have often wondered if at some point in the future, the advancement of technical knowledge will reach a limit. That limit being in the form of the human life expectancy. What I mean is that things will become so complex that it will take the smartest among us their whole life just to learn what is already known. It's somewhat like 'response time' the limit of which is the speed of electricity, current travels 9 inches in one nano-second and that is as fast as it will ever get. Anyway on to motor oils and how they are made. We all know that a lot of byproducts come out of the crude oil refining process, and one of these is the 'base stock' of hydrocarbons our oils are made of. At least this is how our mineral-based oils start out. Synthetics oils are built in the laboratory, so to speak, all be it a very large one. The base of a synthetic is synthesized or built up molecule by molecule from ethylene. Carbon molecules are built up into the chains mentioned in part one. Thus this base stock is 100% uniform unlike mineral base stock. What follows is a component by component description of the most common elements that go into motor oil:

BASE STOCK AND VISCOSITY IMPROVERS: I just talked about base stocks but the chemistry is far too complex to get into here. However the multi grade aspect of oil is achieved by the use of polymers which are complex carbon based chain molecules we have talked about. At low temperatures, they are in the form of tight balls so they flow well. As oil temp rises they unfold into long chain polymers which interweave to increase the oil's viscosity or resistance to flow. Thus the oils tendency to thin out at high temperatures is controlled.

POUR POINT DEPRESSANTS: Here we are entering an area of BIG TIME controversy! Mineral base oils contain many different hydrocarbons, some of which tend to crystallize into waxy material at low temperatures. Pour point depressants are chemicals, which reduce the size of wax crystal formation. This is where we run into a little problem; some oil companies (Castrol) are using a hydroisomerized process to chemically change these wax-creating molecules. This is great except for the fact that they call the resulting oil product 'synthetic' when if fact it is not! At least it's not in the sense of the word we all understand. This perhaps explains why Castrol Syntec shows no increase in horsepower over mineral-based oil. There is a very good write up on this subject in Patrick Bedard's column in the November issue of 'Car and Driver'.

DETERGENTS: These chemicals are usually metallic based and control deposits and keep engines clean. They not only control deposits but clean existing ones and disperse insoluble matter into the oil. These kinds of contaminants result from high temperature operation.

DISPERSANTS: These ashless organic chemicals control contamination from low temperature operation. Both disperants and detergents attach themselves to contaminant particles and hold them in liquid suspension. The suspended particles are so finely divided that they pass harmlessly between mating surfaces and through the oil filter. They are removed when the oil is changed.

FOAM DEPRESSANTS: Detergent and dispersant additives can cause aeration and foaming of the oil. This is bad news for lubrication and air is a very bad lubricant! A foam depressant controls this tendency.

OXIDATION INHIBITORS: Is there anything that oxygen does not attack? Don't answer that. Anyway, these agents reduce oxygen attack of the base oil.

CORROSION INHIBITORS: Acids are a byproduct of combustion and the oil degradation process. Unless neutralized, acids can cause rapid deterioration of engine components. Fortunately corrosion inhibitors do and excellent job of protecting non-ferrous metals by coating them with a protective barrier.

RUST INHIBITORS: Another by product of combustion is water and rust inhibitors protect steal and iron (most cylinder walls are made of iron) from oxygen attack, by forming a protective coating.

ANTI-WEAR AGENTS: These agents prevent wear due to seizure of rubbing surfaces. Compounds such as zinc dailkyt-dithiophosphate break down microscopic hot spots and form chemical filler, which eliminates metal-to-metal contact.

You could write a book on each of the above additives (well you can't and I can't but you get the point). This at least gives you an idea about what goes into your oil. The way these components are formulated and the ratios of there mixture involve a TON of chemical engineering! Do you really want to pour that miracle oil additive into you engine? Slick 50 anyone; I think NOT!

As we can now plainly see there are a lot of different oils and a lot of different things that go into them. One of the subjects that is a real moving target is break-in and oil. When an engine is new or green, there are microscopic high spots and clearance variances even in after the best machining process. Although I should quickly add that machining is far better today with CNC (computer number controlled) machines and laser measurement and compensation control. Never the less a new motor is tight and will run hotter as a consequence. Additionally many new parts need to 'relax' into there final running from. For example if you were to take a brand new aluminum piston and baked it in your oven at 575degees for and hour, it would emerge in a contorted shape. It does not do this inside your engine because its adjacent parts keep it in form. Several heating and cooling cycles will serve to achieve this relaxation. Many of you may know Bill Jenkins (a very well known U.S. Pro Stock drag racer), he preferred to start his engine building process with an engine block (Chevy cast iron) that had performed at least 100,000 miles of service. Why, because the re-machining work done to the block was more stable. So during break-in heat is a problem, keeping RPMs down serves to keep heat down, but another aspect of break-in requires some RPMs or at least some serious combustion pressure.

I think everyone knows that some vehicles of the same model type run stronger than others. The primary reason for this is good piston ring seating (there are others), which gives a better seal and thus more power. During the ignition stroke, or power stroke your engine is making power by virtue of pressure caused by the expansion of the burning combustion charge (not the explosion, the burning). If you can design a motor that burns it's charge quickly and at the right time, you will make a lot more power. An old trick many of or fathers used to get more power, was to advance the ignition timing to a point just short of detonation. I can remember going for rides with my dad to listen for knock as he floored the car while driving up hill (my ears were better). If I heard any knock, he would back the timing down a little. While this did give more power, it is only because of the inefficient combustion chamber design of those old V8s. What was actually going on here was the removal of the 'factories' ignition timing safety margin.

So peak combustion pressure was occurring over a more favorable range of crank rotation degrees, this made more power but at the cost of occasional detonation (so of us would say any is too much). Those engines ignited their charge well before top dead center because it took time for the flame front to progress and for the pressure to build. After the piston passes top dead center it enters a 'sweet spot' of crank rotation degrees were the pressure will do the most work. After 45 degrees passed TDC, the ever-expanding space of the combustion chamber along with lessening crank leverage serve to reduce work and power. So what it all means is that a lot of pressure over the right range of crankshaft rotation degrees with a good ring seal will maximize torque.

The only factor in all this we have any control over, is 'ring seal'. In order to get a good seal the ring and cylinder wall must come into contact and form an even wear pattern. Combustion pressure is what is needed to produce this contact. But heat is a result of high combustion pressure and that's a problem as described above. The answer is to give short bursts of 'deep foot' throttling. Varying RPM also helps but don't accede the manufactures RPM limits. Some of us never 'get on it' so we are not helping our rings seat. So the miles needed to break in a motor vary from one driver to another (they have to put something in the owner's manual so the put in a safe figure). Finally we come to the oil, which as we can see is working very hard during break-in. The two big questions are when should I change the oil first, and when should I put in synthetic (which I assume you want to do).

During the first 600 or so miles most of the metal that's going to go into the oil (from seating and run in) will have done so. So in a new motorcycle you make the change and get the metal out. But our TTs are not going into Audi for the first service until 5000 miles. Is that a problem? I say trust Audi, they use a synthetic oil straight from the factory and we need to assume they know what they are doing. Also assume your filter is holding anything big enough to cause concern. So why the question about changing to synthetic if it's there form the start? I am convinced that the oil formulation Audi uses is a special break in blend and must be left in for 5000 miles (although I changed to Valvoline mineral based at 2500). Mobil 1 makes many different formulations of oil; they all are called Mobil 1. The problem with true synthetic oil is that it is too slippery to allow the wear needed for good ring seating. Although the top manufacturers have extraordinary control over their ring and cylinder machining to the point that a good seal is almost assured, I still would follow the no refill with synthetic rule until at least 5000 miles (I held off until 9000). Don't forget that not all new engines come from the factory, rebuilds and build ups or any motor with plasma moly or chrome rings, can't use synthetic at all until broken in. One reason I said that this is a moving target is because new cars are synthetic ready, not the case with some older models. If you put synthetic in an old car with a rope-style main seal it would leak all over the place. I remember a case with a local police car using Mobil 1 right after it came out. The car's engine burned up and it was all over town. I was against synthetics for many years after that, when all the while it may have been a case of the sump going bone dry (now I know better).

Well what's left, I guess just filters and oil changes. Filters won't take long, buy OEM or factory filters, end of story. Years ago I put a Fram filter on my brother in laws Golf, at start up there was a quart of oil on the ground faster than you would believe, the filter was defective (this is only one of several stories I could tell). I just don't believe in non-factory filters. There is very little reason to change your oil at home any more as it is so cheap to have it done (and free with Audi). If you do, like me, make sure you dispose of it properly, dumping is NOT cool. Also you need to support your vehicle the right why or prepare to die. There are some issues when taking your car in for an oil change. Will they use the oil you specify (bring it to them) and will they use a good filter? With Audi I doubt you will have a problem but when the free service is up you need to take some precautions. A place like Jiffy Lube many have a close filter fit but not a perfect fit, again bring your own filter and oil and watch them pit it in (because there are cases were they haven't-human error).




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