For 1990-2009 cars

# STRAIGHT TIPS ON ENGINE OIL- AN UPDATE

#### VEHICLES AFFECTED: All Passenger Cars and Light Duty Trucks

STRAIGHT TIPS ON ENGINE OIL -- AN UPDATE --

As one popular comedian might say about engine oil, "It don't get no respect." And he'd be right. People tend to ignore the oil in their vehicles, often leaving it to work long past the point where it can do much good ... assuming they used the right kind of oil to begin with.

Recently, for example, we interviewed 390 drivers in four cities: Tulsa, Savannah, Milwaukee and Detroit. We asked if they knew the recommended oil for their cars or could pick it from a chart we showed them.

Guess how many flunked the test. Nearly 95 percent. In other words, 19 people out of 20 didn't seem all that concerned about the well-being of their engines. This puzzles us, in view of oil's critical role in engine operation. But then, maybe they don't know how important oil really is.

How about you? Is your oil I.Q. up to snuff? Let's find out. If you can answer the following questions correctly, you won't have to read the rest of this bulletin. Here we go.

Why does it matter what kind of oil you put in your vehicle? (In this bulletin, vehicle means passenger car, van, or light-duty truck.)

Without checking your Owner's Manual, what quality and viscosity oil does your vehicle call for?

Under what conditions should you follow the short oil-change interval, and when can you follow the longer one? (Yes, there are two different maintenance schedules for changing oil.)

And last, a question we tossed in for the fun of it: Would you be willing to bet that the oil level in your engine is presently above the 'Add' mark on the dipstick? Only a 'yes' response counts as a right answer.

(Time out so you can check your answers and your oil.)

OK, anyone get a perfect score?

Well did anyone get at least three right?

If you didn't that's not too unusual. So let's continue.

WHY IS THE RIGHT OIL SO IMPORTANT?

Before World War 11 when practically all cars had gasoline engines, the engines used little more than straight mineral oil.

That's all they needed. But put that same oil in one of today's cars, and you could damage the engine in a hurry. Here's why:

Engines have been continually improved to work harder and thus have needed more and more internal protection.

Our hectic way of life has made increasingly greater demands on cars and trucks ... and oils.

Recommended oil-change intervals have gotten longer, requiring the use of higher quality oil.

There are a lot of diesel-powered cars and light-duty trucks on the road today. And diesels need a special kind of engine oil (along with more frequent oil changes).

#### BUYER BEWARE

Now you may be thinking, 'Wait a minute! Why talk about the oil used decades ago? Who's going to dump an outmoded oil into an engine of today?'

Brace yourself. It's possible you could ... unwittingly of course. Our surveys show that such low-quality oils (for example SA or SB, see page 8) can still be found in some stores! Overall, the cans don't look any different than the good stuff; so if you don't read -- and understand -- the labels, you might get hooked by the low price. Such oils always seem to be 'on sale,' but they would be a bad buy at any price.

All right, so much for the consumer warning. Now let's take a closer look at the four trends mentioned above.

#### ENGINES WORK HARDER, NEED MORE PROTECTION

For years, engine horsepower climbed rather steadily, putting greater loads on parts like camshafts and rocker arms. Then in 1976, engine downsizing began. But performance requirements stayed high, which kept most engines hustling.

The average operating temperature of oil also went up since WWII, thanks to the increased work done by the engine. In addition, pressurized cooling systems, emission control devices, and the growing use of power options (especially air conditioning) pushed the heat load on the oil even higher.

WE'RE TOUGH ON ENGINES TODAY ---------------------------- We Cruise the Expressways for Long Periods. Such operation exposes the oil to continued high temperatures that can keep oxidizing the oil till it gets as thick as grease if not changed.

We Pull Campers and Trallers. Brutal! Oil can't protect nearly as long because the higher heat load causes rapid oil thickening.

We 'Short Trip' Our Engines to Death. Here's another kind of driving that's hard on the engine: The quick hop to the store, to the movies, to church.

According to the U.S. Department of Transporation, about three out of four car trips made today are for distances less than 10 miles. However, lubricant engineers at the General Motors Research Laboratories have found that it takes as much as 15 miles of driving to fully warm up the oil.

So what happens? When trips are short, condensed water and fuel contaminants in the oil don't get a chance to evaporate completely. And that leads to formation of rust and corrosive acids.

We Do a Lot of Stop-and-Go Driving. That's life in the city. Nevertheless, stop-and-go driving is rough on an engine, mostly because the engine idles a lot. Frequent idling can mean low engine temperatures and more gasoline dilution of the oil. The result? Look out for corrusion and sludge.

#### OIL IS BEING USED LONGER

Through the years, improvements in engines and oils and the use of unleaded gasoline have allowed General Motors to keep extending the recommended period between oil changes. At one time the interval was every 2,000 miles for gasoline engines. Today it's as high as 7,500 miles, depending on the vehicle and how it's used.

The point here is this: GM's current oil-change recommendations are now more liberal because they are based on the assumption you are using high-quality oil, as advised. If you're not, you're rolling the dice and betting your engine.

#### AUTO DIESELS HAVE ARRIVED

At one time the diesel was strictly a workhorse engine. The very word conjured up images of throbbing trailer trucks, earth movers, locomotives.

But because it is more fuel-efficient than the gasoline engine, the diesel eventually found its way into Domestic passenger cars, vans and light-duty trucks. Today diesel-powered vehicles are commonplace.

That doesn't necessarily mean you can use the same motor oil used in gasoline engines. The diesel needs a particular type of oil. Putting in anything else is asking for trouble, especially if it's a low quality oil.

WHY ENGINE OIL LASTS ONLY SO LONG

Maybe you've heard the old saying, 'Oi1 never wears out.' Well, forget it. Oil does wear out; at least engine oil does. To appreciate why, we need a bit of background information.

#### WHAT IS ENGINE OIL ANYWAY?

The story begins with crude petroleum from oil wells. At the refinery the crude is separated by heating and distilling into gases, light fuels, solvents, and lubricating-oil base stocks. After being further processed, the base stocks are selectively blended and fortified with additives to produce an engine oil with the desired properties.

Engine oil, then, is a sort of prescription. It contains different ingredients to do different things. Some of these things are done by the base oil, the rest by the additives.

#### WHAT IS ENGINE OIL SUPPOSED TO DO?

It Should lubricate. That's its primary job to provide a separating film between moving parts and thus control friction and wear. But any kid who ever oiled a pair or roller skates knows that. So what else should it do?

It Should Cool. Engine oil is the principal coolant for the pistons, main bearings, rod bearings, and camshaft. As such, it removes up to 10 percent of the total heat load generated by the engine.

It Should Seal. The sealing we're talking about here is the sealing of combustion pressures. Even though most pistons have two compression rings and an oil ring, high pressure gases can still leak into the crankcase through ring gaps and microscopic valleys in the cylinder walls. This normal leakage is called 'blow-by.' We depend on oil to fill in the valleys and reduce that leakage. Oil, however, can't be expected to seal the canyons in a badly worn engine. Nor can it effectively seal a brand new engine until the parts have seated themselves. That's why oil consumption may be higher for the first few thousand miles of new car operation.

It Should Keep the Engine Clean. Combustion contaminants and dirt in the oil are unavoidable. Such particles tend to clump. If clumping is allowed to take place, sludge and varnish may follow.

Good engine oils are designed to prevent the particles from clumping and, furthermore, to hold them in suspension. Thus when the oil is drained, the suspended particles come out with it.

It Should Make Starting Easier. This is strictly a cold weather requirement. When it's freezing outside, an oil should be thin enough to give the engine a fair chance of starting. Yet as the oil gets hot and thins out, it should not become so thin that it won't lubricate or seal properly. That's what multigrade oils are all about. Some of them are designed to work in almost any temperature range.

It Should Prevent Rusting and Corrosion. Can metal actually rust or corrode in oil? You bet it can, if the oil contains water or acids from the combustion process. A well-formulated oil protects against rusting by putting a chemical film on metal parts, shielding them from the water. It protects against acid attack by neutralizing the acid, in much the same way as stomach antacid tablets work.

#### SO WHY DOES ENGINE OIL WEAR OUT?

Because of additive depletion, for the most part. Just as the chemicals in a flashlight battery have a limited life, so do the additives in engine oil. In the process of doing their jobs, both types of materials get used up. When that happens, the desired effects stop. The battery no longer produces electricity. And the depleted oil no longer protects the engine.

ADDITIVES: WHAT THEY DO

Additives are chemicals that give fresh engine oil its custom-made properties. Although used in small amounts, they provide a tremendous boost to the performance abilities of engine oil. In fact, they represent the major difference between the oils of the early 1940s and the highly advanced prescription oils of today. But what are some of these additives? And how to they work?

#### THE MOST COMMONLY USED ADDITIVES

Antiwear Agents. In highly loaded parts like camshafts and valve lifters, an oil film is usually squeezed so thin it breaks. This could mean damaging metal-to-metal contact. But antiwear agents serve as a backstop in such situations. When the oil film breaks, these agents react chemically with the metal surfaces and immediately form a protective coating that reduces wear.

Detergent-Dispersants. As we've already mentioned, combustion contaminants and dirt particles in the oil tend to clump, which can lead to sludge and varnish deposits. Detergent-dispersants are the additives that not only keep the engine clean but stop such particles from massing. They work by surrounding the particles, most of which are invisible, with a shell of molecules. This action causes the imprisoned particles to repel one another. It also makes them a part of the oil, like cream is part of homogenized milk. Hence they cannot settle out on engine parts or clog oil passages.

Oxidation Inhibitors. These are additives put in oil for the sake of oil. Today's engines run hotter than engines of the past. You may have wondered what's so bad about that; oil still lubricates when it's hot.

What's bad is 'oil oxidation.' Oxidation is a complex chemical reaction between oil molecules and oxygen. As the operating temperature of an oil goes up, so does the oil's oxidation rate. And unless an oil is heavily enriched with additives to fight oxidation, all sorts of undesirable things could happen. The worst of these is that the oil gets thicker and thicker permanently.

Thus if a driver waits too long between oil changes, or uses low quality oil and embarks on a cross-country trek during the summer, he or she may find the oil oxidized to a mess so thick it won't drain out of the crankcase. It happens. Especially when pulling trailers.

Rust and Corrosion Inhibitors. For every litre of gasoline burned, about a litre of water forms as steam. Most of the steam goes out the tailpipe. But some of it leaks into the crankcase, where it becomes an acidic condensate. Water build-up in the oil is made even worse by short-trip driving. If it weren't for rust and corrosion inhibitors and regular oil changes, our engines would be in a heap of trouble because of that water.

V.I. Improvers. 'V.I.' stands for 'viscosity index', 'viscosity' is resistance to flow. Oils having a high viscosity index tend to thin out less when heated and thicken less when cooled. Thus, V.I. improvers are used to raise an oil's viscosity index, giving better all-season performance. Without them we wouldn't have multigrade oils.

Foam Inhibitors. No question about the purpose of these additives. Foam can result from air being whipped into the oil by moving engine parts, which could lead to oil loss, hydraulic valve lifter noise, and improper cooling and lubrication. Foam inhibitors weaken the surface tension of oil. This causes the air bubbles to break more readily.

Pour Point Depressants. The pour point of an oil is the lowest temperature at which the oil will flow. Below that temperature, wax crystals form, grow, and interconnect ... solidifying, or 'freezing,' the oil. Pour point depressants lower this freezing temperature by coating the wax crystals as they form, thereby checking crystal growth.

Friction Modifiers. These are the newest member of the family of additives in modern oils. They further reduce surface friction between moving parts. Friction modifiers, along with low viscosity, make 'Energy Conserving' and similarly labeled oils possible. Such oils can increase a vehicle's fuel economy by about two percent.

#### A WORD TO THE WISE

Remember, even with a first-rate base stock, engine oil is only as good ad the additives it contains. When the additives get tired, so will the oil. And you can't revive it.

Some people have the notion that pouring a can of supplemental additives in the old oil will restore engine protection. It won't. Besides, suppose the old oil is diluted with gasoline, or loaded with dust and diesel soot, or already thickened from oxidation. Additives can't cure any of these aliments.

So what's the message? When it comes time to replenish the additives, do so by changing the oil. And, incidentally, when refilling with fresh oil, don't throw in a can of additives for good measure. That's money down the drain. Worse yet, extra additives could upset the oil chemistry and create new problems. The type of oil General Motors recommends has all the additives your engine needs, in the right amounts.

UNDERSTANDING OIL CAN LABELS

When was the last time you read an oil can?

You say you don't read oil cans? Most people don't ... but they should.

You should know not only what oil is right for your engine, but also if the oil you're buying fills the bill. If you rely on others for advice, you may be following the blind.

A few months ago we went shopping for some oil, visiting a total of 14 gas stations, department stores, auto supply houses and quick-change oil centres. Acting confused, we asked, 'What do you recommend for a late-model diesel car?' Do you know how many right answers we got? One.

So if you want to protect your automotive investment, do your homework. Become your own adviser. Actually, once you learn the language - and you can do it in a minute - it's kind of fun. You can confidently attack oil shelves, inwardly smiling, knowing ... 'I wouldn't put this oil in my lawn mower; this one's too thin; here's one that's right on; so's this one and it costs less and so on.

OK, what do oil cans tell you? They tell you two things: First, the oil's performance rating, or how good it is; and second, the oil's viscosity grade, or how thick (or thin) it is. Let's take them in order.

#### OIL PERFORMANCE RATINGS

Oils are rated by how they perform in engine tests, rather than on what they contain.

These tests, developed jointly by the auto and oil industries and allied societies, represent different engine requirements. Thus an oil may be rated only for vehicles up to a certain model year. Or it may be rated for use in gasoline engines but not in diesel (or vice versa), and so on. The various ratings are labeled by the American Petroleum Institute (API) and are called service categories.

How do you know which is which? Oils for use only in gasoline engines fall under the S category. The S designations run from SA to SF, as defined below.

API SERVICE CATEGORIES

FOR GASOLINE ENGINES ONLY

SA Straight mineral oil.

SB Oil with some additive protection.

SC Recommended for the '64 and previous models.

SD Improved for the '68 and previous models.

SE Further improved for the '72 and previous models.

SF Further improved for the '81, previous, and current models.

Oils for diesel-powered cars and light-duty trucks are special blends. Accordingly, they bear a combined S and C designation. (Oils identified with only a C were initially intended for use in big diesels, like heavy trucks and bulldozers; by themselves they don't suit our needs.) The combined S/C service categories are explained below.

API SERVICE CATEGORIES FOR DIESEL ENGINES IN GM CARS, VANS, AND LIGHT-DUTY TRUCKS

SE/CD* Recommended for the '78 models only.

SE/CC* Recommended for the '79 models (but not for use in the '78s).

SF/CC For all models

SF/CD For all models and preferred in some.

*In case you're wondering, these are not out of order. SE/CD was recommended before SE/CC.

THIS THING CALLED 'VISCOSITY' ------------------------------ Viscosity, as you'll recall, is resistance to flow. Thick oils have a high resistance, and therefore a high viscosity. Thin oils have a low resistance, and by the same token, a low viscosity. By design, all engine oils exhibit their labeled viscosity at 100 DEGC (212 DEG F), or one of six subfreezing temperatures, or some combination of both.

How does a can of oil show viscosity? By an SAE (Society of Automotive Engineers) number. This organization handles the viscosity grading of oils, both single grade and multigrade.

Single-Grade Oils. 'Single grade' refers to oils whose labeled viscosity applies at one temperature only. In general, single-grade oils indicate their viscosity by a single number, for example SAE 10W or SAE 30. The higher the number, the thicker the oil. The W (for winter) tells you that the labeled viscosity applies at one of the subfreezing temperatures. Otherwise it applies at 100 DRG C (212 DEG F).

Trouble is, most 'warm-weather' oils thicken when the temperature drops which makes cold-engine starting very difficult or downright impossible. And many 'winter' oils thin out too much in warmer weather, which hurts their ability to lubricate and seal. This is why drivers who use single-grade oils must change oil to fit the season.

Multigrade Oils. These oils make seasonal changing unnecessary. They contain V.I. improvers that enable each oil to exhibit suitable flow properties at both ends of the thermometer. That's the main reason they cost more than single grade oils.

Hence they bear labels like SAE 5W-30 or 10W-30 or 15W-40 (along with bell ringers like SAE 5W-10W-20W-30 ... in such a case, just ignore the middle numbers and read the oil as SAE 5W-30, which is what it really is).

WHAT DOES GM RECOMMEND?

Officially, General Motors makes oil recommendations through the Owner's Manuals it puts in its vehicles. But, as you know, these recommendations change every so often. What was good for, say, a '78 model car may not be good for today's counterpart.

However the advice GM gives for its current models does apply to the '78s and, in fact, to all passenger cars, vans, and light-duty trucks ever built by GM. We're therefore going to present this advice so that everyone may benefit from the latest technological advances it reflects.

#### THE OIL QUALITY TO USE

Go with the best type: SF oil for gasoline engines only, and SF/CC or SF/CD for diesels and gasoline engines (see Page 13). SF/CD is preferred for some diesels.

Always insist upon these types when having your oil changed. And buy nothing else if you do your own changing (more than half of you do, we've learned). But keep a sharp eye; some cans look like alphabet, soup. You'll have to wade through a lot of letters and phrases.

Don't let all this throw you, though. Just look for the ratings SF, SF/CC, or SF/CD. If you pick up a can of oil and spot these symbols anywhere on the can, even if the S and C symbols are separated from one another, you'll know you're holding a high quality engine oil (assuming, of course, a responsible company packaged the product).

#### THE RIGHT VISCOSITY

Remember, you need the right viscosity for easier cold starts in the winter and for adequate lubrication and sealine in the summer. So for engine operation in a wide range of temperatures, we recommend multigrade oils, specifically those labeled 'Energy Conserving' or 'Fuel Economy' or words to that effect (see Page 13).

The lone exception to this advice is that when the average temperature is above freezing, we suggest using SAE 30 grade oil in the 4.3 litre, 5.7 litre, and 6.2 litre diesel engines.

#### WHAT ABOUT SYNTHETIC OILS?

If a new breed of oil came along that could truly outperform conventional oils at a reasonable cost, we'd be as excited as anyone. So, naturally, we checked out the synthetics.

What did we find? Well, compared with conventional motor oils, the synthetics involve different chemical processes and ingredient percentages. However, the base stock still comes from crude petroleum, and the additives are virtually the same as those commonly used.

From a performance standpoint, they work well, especially for engine starting at very low temperatures. But based on all the information we now have, we can't comfortably advise you to leave synthetic oile in your engine any lorger than conventional oils (extended use is the principal claim of synthetics). Use them if you want, as long as they bear the right service category and viscosity grade for your vehicle and you change oil as specified in your owner's Manual.

#### WHEN TO CHANGE OIL

'When should I change my oil?' you may ask. As soon as the additives give out, of course. But that varies with the kind of engine you have, the conditions under which you drive, etc. Since we can't cover all bases here, you'll have to check your Owner's Manual for the exact oil-change recommendations that apply to your vehicle.

We do want to mention a couple of things, however. One is to remind you that for many many years General Motors has recommended two different mileage/time maintenance schedules for changing oil: A short oil-change interval, based on conditions that make greater demands on the oil. And a longer interval, based on the maximum limit considered safe for a vehicle.

Our impression is that the short oil-change interval tends to get ignored.

But I Baby My Car. 'I live only four miles from work. The shopping centre's right down the road. I'm not a hard driver. Why can't I use the longer oil-change interval?'

Hey, we're sympathetic. We admit that on the whole, your vehicle has it easy. But your engine won't agree. It's slowly loading up with condensate (especially in freezing weather), which the oil can't tolerate for long. To your engine, this is rough duty.

So is regular driving in dusty regions of the country, pulling a trailer for several hours at high speeds, and prolonged idling. Under these conditions, oil additives deplete much faster than they do under less severe operating conditions calling for the short oil-change interval.

Check It Out. The other point we want to make concerns checking your oil level. Time was when gas station attendants routinely did that job. Not anymore. Today, self-service is the in-thing, as you're well aware. Now, we're the attendants. We pump our own fuel, and then without looking under the hood we tell ourselves the oil's OK (as if we knew). But often we don't know. In a sampling of drivers we took in several cities, over 20 percent of the engines checked were one or more litres low on oil.

Hopefully, we'll get on the stick and start checking our engine oil more often. All of us. Before oversight allows low oil supply to cause engine damage.

And by the way, the oil light on most instrument panels is not a fluid level indicator. You probably realize that, but at least one person we interviewed didn't. 'Oh yes, I add oil every time the red light goes on,' we were told. Bad news. That is not the way you should check your oil.

#### PUTTING IT ALL TOGETHER

This is the page you'll want to dog-ear for quick reference. In a nutshell, it represents the word ... the state of the art ... GM's latest engine oil advice to you, no matter how old.

How many sayings or claims regarding oil have you neard since you first started driving? Like the one we mentioned earlier ... 'Oil never wears out' (except we now know different).

Quite a few rumours have made the rounds, and new ones keep popping up. Unfortunately, you don't know whether you're hearing good advice, gas station legends, or somebody's uncle's opinion. Here is a list of some common myths we'd like to take apart:

'Don't Put Detergent Oils in Old Engines.'

This one sounds logical at first. It's easy to imagine the detergent loosening up the accumulated goop and caked carbon. You can picture this stuff playing havoc inside the engine. Clogging the oil screen. Jamming the lifters. Messing things up in general.

But that's not what happens. It's true that detergent-dispersants remove some of the existing deposits. However, they work gradually and do not dislodge large masses. Their main mission is to prevent the deposits from forming in the first place. In fact, all GM-recommended oils contain detergents.

'A Dirty Dipstick Means a Dirty Engine.'

It could. But not in an engine that's been properly maintained. There, a dirty dipstick means a clean engine.

A good, fresh oil will start looking dirty shortly after being put to use, in diesels within hours. It's a sign the oil's doing its job of keeping soot, dust, and other contaminants in suspension ... preventing them from collecting and becoming sludge.

'Include a Can of Additives With Each Oil Change.'

Why? Do you add sugar to soda pop? It's the same with oil. If you refill with a recommended oil, the right additives are already there. Enough to last between specified oil changes.

'Never Mix Oil Brands.'

Oils recommended in this bulletin for any given engine may be intermixed regardless of brand name. Just be sure the service category and viscosity grade are OK for that engine.

'Short Trips Make an Engine Last Longer.'

Nooo way. Short trips can be tough on an engine. They allow rapid build-up of water and raw fuel in the oil, which promotes corrosion, wear, and sludge.

So if you're shopping for a used vehicle and hear that classic pitch, 'It was owned by this guy who drove it only a few miles a day,' ask what kind of oil he used and how often he changed it. Could be the engine's in bad shape.

'Oil Filters Keep the Oil Clean, So You Can Use The Oil Longer.'

Unclogged oil filters keep the oll free of solid matter. But they can't remove water, gasoline, and acids. And they can't pinch-hit for additives that get used up.

PARTING WORDS

Before you put this bulletin away, let's review the main points:

Use only top quality oll: SF/CC, SF/CD, SF.

Pick the right viscosity.

Change oil when you should.

Check the oil level frequently.

Whenever you need to, go back and check the oil recommendations on Page 13. They cover practically all of the information you need to know about engine oil. And that's information you can take to the bank.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.