Come on Tim, you're only saying that because you can't afford Royal Purple...J/K

 

Doctor D Thanks for all the info on oil. Some people on this site need to lighten up. If your bored with the thread, move on!

 

The Royal Purple is still sitting on the shelf of my Wally World. The locals here in S.A. like the color of the bottle, because it matches the lights around their tag & underbody. They shake it a few times. Look at each other. Shake it some more. Then put it back on the shelf, and buy the Quaker State......

I buy motorcraft 5-20 because I change my oil every 3-4 months since my truck sits sometimes for weeks....its humid here.

 

Price?

 

People up there must not know much about oil...

 

Oh, You mean like differences in wax?

 

No, I'm saying that because test after test has shown that the proper weight oil changed every 3,000 miles will protect your engine. Period.

And test after test has shown that the real-world differences between synthetics - even with the loose use of that term - are pretty close to nil.

Yes, these differences are important to engineers. And once they stack up those minute differences over a few decades, they matter, i.e., oil that is meaningfully better emerges. But to debate which current synthetic is better is an academic exercise. I would not hesitate to use any of them.

 

Perhaps that's because the synthetic users tend to take better care of their cars.

Personal observations with unknown variables is no substitute for controlled testing in double-blind, real-world testing.

"Consumer Reports:

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.

. . .

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 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.

. . .

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 modern 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.

[continued]

 

[part 2:]

Recommendations:

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."








Of course, solid scientific testing like this won't stop the oil chatter here or anywhere else. The multi-billion dollar advertising campaigns by the oil companies will continue to brainwash us into thinking that one brand of oil is meaningfully better than another, despite a mountain of evidence to the contrary.

 

Good info Tim, but I doubt any of those taxi cabs were drag racing on the weekends and possibly towing thousands of pounds. I believe under these conditions are where the synthetics out-perform the conventional oils.

 

Could be, but that is arguable.


I agree. However, personal observation with unkown variables is also about as objective as you can be. Because the history is completely blind to the observer. Example: when a radiologist looks at radiographic images, they do not know the patient, nor the patient history. They look at the image and describe the findings, then draw conclusions.

BTW, you quoted Consumer Reports. I got castigated for that some time back. Apparently, and according to several members of this forum, they are a very biased organization, thus their conclusions have a foundation built on sand....according to some.

 

Agreed 100%. That's why I included the parts that said:

"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."

and

"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."

Not to mention documented better HP, especially with the thinner oils.

I'm a firm believer in synthetics. But I'm a confirmed skeptic about inter-brand differences.

 

Flawed analogy. The radiologist is looking for a condition, not its cause. To find its cause, other data is needed. And then variables have to be isolated.

Perhaps the most common logical flaw in society is confusing temporal or statisical relationships with causal relationships.

Example: Men who play professional football are large. Therefore, playing football must make one large.

Flaw: The unknown variable is a comparison of the size of people signing up to play football. Since small people are underrepresented in the sample group to begin with, the size of the people when they begin playing must be measured and accounted for.

In your assumptions regarding engine condition, you did not account for the fact that synthetic users service their cars better. In this author's mind, that's not a "maybe," that's a fact. But even if you dispute it, you should recognize that this is a critical variable that must be controlled before your personal observations can be considered scientifically meaningful.

 

Many Consumer Reports testing seems stupid to me. But this one was incredibly well documented, and as mentioned in the above passage, is in fact also used by the oil companies themselves.

Find a better study. I'm all eyes.

 

Tim, even though we are on the same page on this because I agree with you, one word, and it is the KEY word, that these engineers continue to use is "ADEQUATE".

I've said it many times, just about any regular vehicle will survive 100K+ miles on the cheapest dino out there and regular maintenance.

If someone wants to settle for mediocrity, that is up to them. I will go for the "exceptional" oil.