Article from Consumer reports on Auto Oil in 1996

Storm Trooper

Home is where you park it!
Feb 14, 2008
Where my camper is parked now.
Consumer Reports:Truth Motor Oils- July 1996 +

The surprising truth about motor oils
July 1996, pp 10-13

Our 4-1/2-million-mile test with a fleet of New York City taxicabs turned some conventional wisdom on its head.

Mobil commercial claims its oil "has been in more Indy 500 winners than any other oil." Quaker State shows an engine with a terminally corroded inside what they imply could happen when you use another oil. Exxon's commercial for its Superflo oil urges motorists to "rely on the tiger."

Oil companies spend millions of advertising dollars each year to convince you that their oil can make your car's engine perform better and last longer. And purveyors of motor-oil and engine "treatments" assert that their products offer engine protection that oil alone can't provide. In our most ambitious test project ever, we set out to discover whether such claims are fact or fancy.

One way to gauge the performance of motor oils is to test them on the road. We did just that, using a fleet of 75 New York City taxicabs. Indeed, the oil industry itself tests its oils in New York City taxis.

For 22 months, we tested the performance of 20 popular motor oils. Each of those oils met the industry's latest standards, as certified by a starburst symbol on the container. (See "It's not just oil," article 3 of 4.) We also tested Slick 50 Engine Treatment and STP Engine and Oil Treatments.

In addition to the taxicab tests, we had the oils' chemical and physical properties analyzed by an independent lab. We also surveyed our subscribers about their oil-changing experiences and preferences, and we sent shoppers to quick-lube centers across the country to assess the service. Finally, because changing the oil is just one part of car care, we've reviewed some other ways you can help keep your car running longer. That report begins on page 18 (not included in this e-mail).
Testing the oils

We put identical rebuilt engines with precisely measured parts into the cabs at the beginning of the test, and we changed their oil every 6,000 miles. That's about twice as long as the automakers recommend for the severe service that taxicabs see, but we chose that interval to accelerate the test results and provide worst-case conditions. After 60,000 miles, we disassembled each engine and checked for wear and harmful deposits.

Our test conditions were grueling, to say the least. The typical Big Apple cab is driven day and night, in traffic that is legendary for its perversity, by cabbies who are just as legendary for their driving abandon.

When the cabs aren't on the go, they're typically standing at curbside with the engine idling - far tougher on motor oil than highway driving. What's more, the cabs accumulate lots of miles very quickly, making them ideal for our purposes. Big-city cabs don't see many cold start-ups or long periods of high speed driving in extreme heat. But our test results relate to the most common type of severe service - stop-and-go city driving.

Each of the 20 oils we studied was tested in three cabs to provide meaningful test results even if a few cabs fell out with mechanical problems or because of accidents. (Six of the 75 engines did, in fact, have problems, none apparently related to the oil's performance.) For a detailed description of our test procedures, see "Testing in the Big Apple," article 2 of 4.

Our shoppers all across the country bought hundreds of quart containers of oil. Some brands had slightly different formulations in different areas, but all the oils included a full package of additives.

The independent lab helped us identify the most representative formulations of each brand. Our engineers transferred containers of that oil to coded 55-gallon drums and hauled them to the fleet garage for testing.

Ideally, oil should be thin enough to flow easily when the engine is cold and remain thick enough to protect the engine when it's hot. The lab analyses of each oil's viscosity characteristics - its ability to flow-indicate that motor oils have improved since 1987, when we last tested them. This time, far fewer test samples failed to meet the viscosity standards for their grade - and those were typically outside the limits by only a slight amount. No brand stood out as having a significant problem.

We tested oils of the two most commonly recommended viscosity grades - 10W-30 and 5W-30. Automakers specify grades according to the temperature range expected over the oil-change period. The lower the number, the thinner the oil and the more easily it flows.

In 5W-30 oil, for example, the two numbers mean it's a "multiviscosity" or "multigrade" oil that's effective over a range of temperatures. The first number, 5, is an index that refers to how the oil flows at low temperatures. The second number, 30, refers to how it flows at high temperatures. The W designation means the oil can be used in winter.

A popular belief is that 5W-30 oils, despite their designation, are too thin to protect vital engine parts when they get hot. However, one of our laboratory tests measured the viscosity of oils under high-temperature, high-stress conditions and found essentially no difference between 5W-30 oils and their 10W-30 brand mates. But at low temperatures, the 5W-30 oil flowed more easily.

Viscosity grade is important, so be careful. Recommendations vary with the make, engine, and model year of the car, so check your owner's manual and ask the mechanic for the proper grade of oil.

Of the 20 oils we tested, nine were conventional 10W-30 oils, and eight were 5W-30. We also tested two synthetic oils, Mobil 1 and Pennzoil Performax, and one synthetic-and conventional blend, Valvoline DuraBlend; all three were 10W-30 oils.
No brand performed best

If you've been loyal to one brand, you may be surprised to learn that every oil we tested was good at doing what motor oil is supposed to do. More extensive tests, under other driving conditions, might have revealed minor differences. But thorough statistical analysis of our data showed no brand-not even the expensive synthetics-to be meaningfully better or worse in our tests.

After each engine ran about 60,000 miles (and through 10 months of seasonal changes), we disassembled it and measured the wear on the camshaft, valve lifters, and connecting-rod bearings. We used a tool precise to within 0.00001 inch to measure wear on the key surfaces of the camshaft, and a tool precise to within 0.0001 inch on the valve lifters. The combined wear for both parts averaged only 0.0026 inch, about the thickness of this magazine page. Generally, we noted as much variation between engines using the same oil as between those using different oils. Even the engines with the most wear didn't reach a level where we could detect operational problems.

We measured wear on connecting rod bearings by weighing them to the nearest 0.0001 gram. Wear on the key surface of each bearing averaged 0.240 gram - about the weight of seven staples. Again, all the tested oils provided adequate protection.

Our engineers also used industry methods to evaluate sludge and varnish deposits in the engine. Sludge is a mucky sediment that can prevent oil from circulating freely and make the engine run hotter. Varnish is a hard deposit that would remain on engine parts if you wiped off the sludge. It can make moving parts stick.

All the oils proved excellent at preventing sludge. At least part of the reason may be that sludge is more apt to form during cold startups and short trips, and the cabs were rarely out of service long enough for their engine to get cold. Even so, the accumulations in our engines were so light that we wouldn't expect sludge to be a problem with any of these oils under most conditions.

Variations in the buildup of varnish may have been due to differences in operating temperature and not to the oils. Some varnish deposits were heavy enough to lead to problems eventually, but no brand consistently produced more varnish than any other.

The bottom line. In our tests, brand didn't matter much as long as the oil carried the industry's starburst symbol (see "It's not just oil," article 3 of 4). Beware of oils without the starburst; they may lack the full complement of additives needed to keep modem engines running reliably.

One distinction: According to the laboratory tests, Mobil 1 and Pennzoil Performax synthetics flow exceptionally easily at low temperatures - a condition our taxi tests didn't simulate effectively. They also had the highest viscosity under high-temperature, high-stress conditions, when a thick oil protects the engine. Thus, these oils may be a good choice for hard driving in extreme temperatures.

Note, too, that a few automakers recommend specific brands of motor oil in the owner's manual. You may need to follow those recommendations to keep a new car in warranty.
Oil changes: How often?

The long-time mantra of auto mechanics has been to change your oil every 3000 miles. Most automakers recommend an oil change every 7,500 miles (and a specific time interval) for "normal" driving, and every 3,000 miles for "severe" driving - frequent trips of less than four or five miles, stop-and-go traffic, extended idling, towing a trailer, or dusty or extremely cold conditions. Many motorists' driving falls into one or more of those "severe" categories.

In our survey, almost two-thirds of our readers said they had their oil changed every 3,000 miles or less. They may be following the thinking expressed by one of our staffers: "I have my oil changed every 3,000 miles because that's what my father did, and all his cars lasted for many years."

To determine whether frequent oil changes really help, we changed the oil in three cabs every 3,000 miles, using Pennzoil 10W-30. After 60,000 miles, we compared those engines with the engines from our base tests of the same oil, changed every 6,000 miles. We saw no meaningful differences. When Mobil 1 synthetic oil came out, Mobil presented it as an oil that, while expensive, could go 25,000 miles between changes. That claim is no longer being made. But Mobil 1 is still on the market, selling at a premium (along with pricey synthetic competitors from several other companies). And synthetic oil's residual reputation as a long-lasting product may still prompt some people to stretch their oil changes longer than the automaker recommends.

Determining whether synthetic oils last longer than conventional ones would require a separate test protect. To try to get some indication, we put Mobil 1 synthetic into three cabs and changed their oil every 12,000 miles.

We intended to compare the results of these tests with those from the three taxicabs whose Mobil 1 was changed at our normal interval, every 6,000 miles. Unfortunately, two of the three engines using the 12,000-mile interval developed problems. (We couldn't attribute those problems to the oil.) The third engine fared no worse than the three whose oil had been changed at 6,000-mile intervals.

The bottom line. Modern motor oils needn't be changed as often as oils did years ago. More frequent oil changes won't hurt your car, but you could be spending money unnecessarily and adding to the nation's energy and oil-disposal problems.

Even in the severe driving conditions that a New York City taxi endures, we noted no benefit from changing the oil every 3,000 miles rather than every 6,000. If your driving falls into the "normal" service category, changing the oil every 7,500 miles (or at the automaker's suggested intervals) should certainly provide adequate protection. (We recommend changing the oil filter with each oil change.)

We don't recommend leaving any oil, synthetic or regular, in an engine for 12,000 miles, because accumulating contaminants - solids, acids, fuel, and water - could eventually harm the engine. What's more, stretching the oil-change interval may void the warranty on most new cars.
Testing Slick 50 and STP

We also tested Slick 50 and STP Engine Treatments and STP Oil Treatment, each in three cabs. (Slick 50 costs $17.79 per container; STP Engine Treatment has been discontinued.) All three boast that they reduce engine friction and wear.

The engine treatments are added with the oil (we used Pennzoil 10W-30). They claim they bond to engine parts and provide protection for 25,000 miles or more. We used each according to instructions.

The STP Oil Treatment is supposed to be added with each oil change. It comes in one formulation (black bottle, $4.32) for cars with up to 36,000 miles, another (blue bottle, $3.17) for cars that have more than 36,000 miles or are more than four years old. We used the first version for the first 36,000 miles, the second for the rest of the test-again, with Pennzoil 10W-30.

When we disassembled the engines and checked for wear and deposits, we found no discernible benefits from any of these products.

The bottom line. We see little reason why anyone using one of today's high-quality motor oils would need these engine/oil treatments. One notable effect of STP Oil Treatment was an increase in oil viscosity; it made our 10W-30 oil act more like a 15W-40, a grade not often recommended. In very cold weather, that might pose a risk of engine damage.

None of the tested oils proved better than the others in our tests. There may be small differences that our tests didn't reveal, but unless you typically drive under more severe conditions than a New York cab does, you won't go wrong if you shop strictly by price or availability. Buy the viscosity grade recommended in your owner's manual, and look for the starburst emblem. Even the expensive synthetics (typically, $3 or $4 a quart) worked no better than conventional motor oils in our taxi tests, but they're worth considering for extreme driving conditions high ambient temperatures and high engine load or very cold temperatures.

On the basis of our test results, we think that the commonly recommended 3,000-mile oil-change interval is conservative. For "normal" service, 7,500-mile intervals (or the recommendation in your owner's manual) should be fine. Change the oil at least that often to protect your engine and maintain your warranty. Even for the severe service experienced by the taxis in our tests a 6,000- mile interval was adequate. But some severe service - frequent cold starts and short trips, dusty conditions, trailer towing - may require a shorter interval. Note, too, that special engines such as diesels and turbos, which we didn't test, may need more frequent oil changes.

We don't recommend stretching the change interval beyond the automaker's recommendations, no matter what oil you use. Engine combustion contaminants could eventually build up and harm engine parts.

As for STP Oil Treatment, STP Engine Treatment, and Slick 50 Engine Treatment, our advice is simple: If you use an oil with the starburst symbol, you don't need them.
Testing in the Big Apple

New York City taxicabs played a key role in our massive test project to evaluate motor oils. For consistency, we used only 1992-93 Chevrolet Caprice cabs. Each received a precisely rebuilt 4.3-liter V6 at the beginning of its 60,000-mile test. We started with six rebuilt engines; after each engine was installed in a cab, the six engines that were removed were rebuilt and installed in six other cabs-and so on. Using that rotation, we monitored 75 cabs over 4-1/2 million miles of driving in New York City and its environs. Each oil was tested in three engines.

A local shop completely machined each engine block and crankshaft, rebuilt the cylinder heads, and installed new bearings, pistons, rings, seals, gaskets, and oil pump. Though the engines originally had roller lifters and camshafts, a design that reduces friction, we installed conventional sliding lifters and camshafts to accelerate wear.

Before the engines were assembled, we measured or weighed the parts most likely to show wear if the oil wasn't doing its job - the camshafts, valve lifters, and connecting-rod bearings. Each cab went through a break-in procedure before hitting the road. During testing, two engine timers measured the time the engine was running and the time it was in gear.

Over the next 22 months, our engineers paid more than 100 calls - usually without notice - on the fleet garage. They dropped off test oil and picked up used-oil samples for ongoing analysis. They also made sure that oil was being added to the engines when necessary and changed as scheduled.

After each 60,000-mile test, we remeasured the key engine parts. We also examined combustion-chamber deposits, the color of the valves, scoring of cylinder walls, and valve-deck deposits for any sign of engine problems.
It's not just oil

Certainly, motor oil is slippery. That's what helps protect an engine's moving parts. But motor oil does much more than lubricate. It helps cool the engine keep it clean, prevent corrosion, and reduce friction to improve fuel economy. To do all that, refiners blend in various additives, which account for 10 to 25 percent of the product you buy.

The oil industry has devised a starburst symbol (described at the bottom of this article) to certify that a particular motor oil meets the latest industry requirements for protection against deposits, wear, oxidation, and corrosion. The starburst on the label means the oil meets API (American Petroleum Institute) Service SH requirements - the latest, most advanced formulation. (Service SH supplants SG, the previous top category.) The CD designation on most of the oils we tested refers to diesel performance. The starburst also indicates that the oil passes ILSAC/GF-1 standards developed by the International Lubricant Standardization and Approval Committee, a U.S.-Japanese group. And it means the oil meets Energy Conserving II requirements - it improves fuel economy by reducing engine friction. All the oils we tested carry the starburst - and all performed well in our tests. But note that oils without that symbol may not perform as well.

Below are some of the additives found in modern oils.

Viscosity-index improvers modify the oil so its viscosity is more consistent over a wide temperature range.

Antioxidants prevent the oil from thickening when it runs hot for extended periods.

Dispersants keep contaminants suspended so they don't form deposits in engine.

Detergents help prevent varnish and sludge on engine parts and neutralize acid formed in engine.

Rust and corrosion inhibitors protect metal parts from acids and water formed in engine.

Pour-point depressants help the oil flow in a cold engine, especially in cold weather.

Foam inhibitors collapse the bubbles churned up by engine crankshaft. (Foam reduces lubricating effectiveness.)

Friction modifiers strengthen the oil film and prevent unlubricated contact between moving parts.

Antiwear agents provide lubrication when oil is squeezed out from between moving engine parts.

The starburst symbol is a circle with a serrated edge about an inch across with text which reads "AMERICAN PETROLEUM INSTITUTE CERTIFIED FOR GASOLINE ENGINES."
Ratings & Recommendations Motor oils
Shopping strategy

Discount stores are generally the least expensive place to buy oil. Look for sales and buy by price - but make sure the container has the starburst symbol.
Details Listed alphabetically

All the tested oils performed well in our tests, and all claim to meet the latest (API-SH and ILSAC/GF-1) industry standards (see "It's not just oil," article 3 of 4). Prices are the average for one quart, based on a national survey of discount stores.
5W-30 oils

Castrol GTX $1.21
Appears to use same formulation in all areas sampled. Graduated container.
Exxon Superflo
Price not available; not widely found in discount stores. Appears to use same formulation in all areas sampled. Graduated container with window.
Fire & Ice All-Season (Shell) * $0.93
Different formulations in Florida and New York. Graduated container with window.
Havoline Formula 3 (Texaco) $1.11
Appears to use same formulation in all areas sampled. Graduated container with window.
Mobil * $0.95
Appears to use same formulation in all areas sampled. Graduated container with window.
Pennzoil $1.16
Appears to use same formulation in all areas sampled. Graduated container.
Quaker State Deluxe * $1.20
Appears to use same formulation in all areas sampled. Graduated container with window. 10W- 30 is called Super Blend.
Valvoline All-Climate $1.14
Different formulations in California and Texas. Graduated container with window.

10W-30 oils

Castrol GTX $1.18
Appears to use same formulation in all areas sampled. Graduated container.
Exxon Superflo $1.13
Different formulation in Florida. Graduated container with window.
Fire & Ice All-Season (Shell) * $0.99
Appears to use same formulation in all areas sampled. Graduated container with window.
Havoline Formula 3 (Texaco) * $1.13
Different formulations in Illinois and Texas. Graduated container with window.
Kendall Superb 100 * $$1.23
Different formulation in Florida. 5W-30 version not tested.
Mobil 1 synthetic $3.76
Low-temperature flow characteristics were better than most. Appears to use same formulation in all areas sampled. 5W-30 version not tested. Graduated container with window.
Mobil $0.95
Different formulation in New York. Graduated container with window.
Pennzoil $1.16
Appears to use same formulation in all areas sampled. Graduated container.
Pennzoil Performax synthetic $2.97
Low-temperature flow characteristics were better than most. No 5W30 version. Appears to use same formulation in all areas sampled.
Quaker State Super Blend * $1.20
Appears to use same formulation in all areas sampled. Graduated container with window. 5W-30 is called Deluxe.
Valvoline All-Climate $1.13
Different formulation in California. Graduated container with window.
Valvoline Semi-Synthetic DuraBlend Conventional/synthetic blend * $2.12
Appears to use same formulation in all areas sampled. Graduated container with window, No 5W-30 version. Flow characteristics were more like those of a conventional oil than those of a synthetic.

* One or more samples differed from viscosity-grade requirement by a small amount.

The table below shows price ranges of five popular 10W-30 oils in discount stores and auto-parts stores, on the basis of a national survey. Discount stores account for an estimated 51 percent of do-it-yourself oil sales; auto-parts stores, nearly 35 percent. Service stations tend to be the most expensive, charging as much as $2.50 a quart.


Super Active Member
Jun 22, 2010
Las Vegas, NV.
I would agree with this article both then and now. Change your oil at a reasonable mileage and use the correct weight for your engine. Synthetic or conventional is fine unless your vehicle specifically calls for synthetic. [2C]

Good post!


Active Member
Apr 28, 2014
The test area was usefully controllable for experimenting; my problem was with "Big-city cabs don't see many cold start-ups". These are widely seen as the conditions which cause most wear.

Storm Trooper

Home is where you park it!
Feb 14, 2008
Where my camper is parked now.
That is a good point, but don't most if not all automakers consider taxicabs under the "Severe Service" maintenance routine?
My point in posting this was that almost 20 years ago, all oils tested by CU met specs after double the amount of mileage required for oil changes.
I'm not recommending that people extend their oil changes beyond the automakers requirement, just that I think auto oils are better than most of us realize.


Super Active Member
Jan 25, 2014
Interesting article, thank you.

What is Rotella byShell? Who uses it and for what purposes?


Super Active Member
Jun 26, 2012
Wylie, Texas
niagarafam said:
Interesting article, thank you.

What is Rotella byShell? Who uses it and for what purposes?

Rotella oil is used in diesel engines and highly regarded as the best. There are MANY oils out there for gasoline engines. With a diesel, up until the last few years, you only have a few to choose from. ND more so recently you still have the same to choose from, but in different viscosity, so you're kinda still stuck with the same brands.

I agree that a 3000 mile oil change is kinda silly. That being said, what's wrong with doing it ahead of time at 3000? Absolutely nothing. My main concern with oil changes are the guys who always came into my shop saying "it's a diesel, I hardly ever have to change the oil". That is debatable. Not only do you have a diesel, you have a turbo as well. Ford recommends 7500 miles in some of its diesels, but I also see a lot of parts being replaced by people who follow that rule. If I recall correctly ford actually modified that 7500 mile rating, I could be wrong on that, so don't quote me.

Great find storm trooper! Quite the interesting read.


Active Member
Apr 28, 2014
Storm Trooper wrote : "don't most if not all automakers consider taxicabs under the "Severe Service" maintenance routine?"

Yes, that's true. Strangely enough I read somewhere that increasingly long service intervals were for the benefit of fleet buyers. They cut their service costs then replaced the vehicles before they went wrong!


Active Member
Aug 3, 2012
The testing of the taxicab engines was valid for the light load city driving that they did, although that type of driving/engine load is not the same as what is done when towing a camper. [:O]

I think that when an engine is worked harder, such as when towing a camper and having multi-passengers, it will routinely use "some" oil, and will run somewhat hotter. With the heavier work load usage, I have found that topping up of oil, even if only for a few ounces or a half quart of oil, is the best way to keep the oil working at its best. I also think that a common sense approach to knowing when to change the oil and filter would be at each 6,000 miles, or when the color of the oil is showing grayish discoloration(crud). :)

The reason for stating the reliance on a shorter mileage range is "likely" because many folks do not check the engine oil level between oil changes, or not at all. [SNZ]


Active Member
Jun 2, 2014
Look at those 1996 oil prices! $1 for a quart. I feel old now, and I am sure there are many old timers on here at remember even cheaper oil.


5 Star Eagle Camper
Aug 5, 2010
Near Elmira, Southern Ontario
Man that was a long read just to hear the guy say, "they're all the same".

I have always been a 4500-5000 km changer, religiously. Thats right in the 3000 mile range.

I just recently got rid of my old TV. It was a 2001 Grand Caravan, 3.3 liter. It had just over 410,000 kms (255 000 miles) on it. At one point, about a year ago, I had to take the oil pan off it because the oil drain plug nut broke off the inside of the pan. I had to weld it back on from the inside. That oil pan was so clean inside, I could've eaten my breakfast cereal out of it, (some of us old time mechanics do that anyway). With the way oil prices are these days, (cheap on the open market, but super expensive on the store shelves), leaving things go a little longer between changes probably wouldn't hurt anything at all.
I still can't bring myself to do it though.


Active Member
Dec 8, 2014
For those who have older vehicles that do not have roller cams in them, you should be adding an additive with zddp in it at your oil changes. The oils mentioned with the starburst have removed this lubricating chemical. It I's difficult to find an oil without the zddp. Zddp has sink and phosphoris which act as lubricants for metal parts When I can't find the additive I run the rottela in my gas truck.


Call me Paul
Jan 28, 2015
Christchurch, New Zealand
Novarich said:
For those who have older vehicles that do not have roller cams in them, you should be adding an additive with zddp in it at your oil changes. The oils mentioned with the starburst have removed this lubricating chemical. It I's difficult to find an oil without the zddp. .
OK that is interesting. I guess our options will be slightly different over here.
But do you have list of oils and what additives are being put into each?


A short run will get you within walking distance.
May 17, 2014
Boulder, Colorado
So glad you shared this article. Now I understand why my mechanic friend in Fraser, Colorado so strongly recommends the synthetic oils for his customers. Up there "cold start" can mean minus twenty degrees!


Active Member
Apr 28, 2012
The internet has existed for over 20 years and some people still change their oil at 3000 miles.


Art & Joyce - Columbus, O
Jul 18, 2013
Thornville, OH
Toyota for my TV indicates every 6K. There is a service bulletin that states if using full syntactic you can increase it to 10K.

I change my oil every 10K


Super Active Member
Jan 25, 2014
I change our TV and sedan every 5K. I use Mobil 1 high mileage synthetic on the Camry, and Royal Purple or Mobil 1 extended life (15K) synthetic on the Ram. I just cannot bring myself to leave the oil in for 8-10K. Just me - I know that I am goofy, but I like to keep it clean and viscous. :)


Retired from the Federal Government
May 7, 2013
Somewhere in Idaho
eoleson1 said:
That's because the guys at Goofy Lube and other quick oil shops are perpetuating that myth.

Going to places like goofy lube for an oil change is like going to a Proctologist for a root canal.