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Last December, I wrote that one of the perks of writing a column like this is the response from readers. Believe it or not, I enjoy the feedback. Often the comments are attaboys which are always welcome. As well, there have been many thoughtful and astute observations, questions, challenges and corrections. I take those very seriously and respond accordingly. This month, Id like to share some of this back-and-forth with you, and maybe clarify a few questions you might have had but didnt bother to ask.

Septembers column on low speed pre-ignition (LSPI) generated many comments, including from Lake Speed Jr. in North Carolina. Noting that the chain structure of the hydrocarbon has significant influence on a gasolines octane rating, Lake wondered if base oil characteristics are of significant importance. He also wondered how blowby from the engines positive crankcase ventilation (PCV) might impact LSPI.

My response is that blowby, which is recirculated into the intake system by the PCV valve, has some detrimental effects on engine operation. However, the advent of the on-board engine computer to manage fuel flow, ignition timing and emissions has pretty much compensated for any negative impact blowby might have created. PCV valves have been on automobiles since the mid-1960s. In fact, the first car I owned (a 57 Chevy with a V-8) had to be retrofit with a PCV valve before I could buy it in 1964.

At this point, the concern most OEMs have is that the engines experiencing LSPI tend to be very small (about 1 liter of displacement) and to operate on fuel charges that are highly compressed through turbo-charging. These engines are so sensitive to anything which may cause the prob-lem that the OEMs want added assurance that the oil isnt a contributor.

As far as base stock composition is concerned, I would think that because only a small amount of oil is getting into the engine, the oil chemistry might not be too significant. Of course, the latest engine oil categories are such that it is almost impossible to meet requirements with any appreciable amount of older API Group I base stocks, which have greater volatility and contain more sulfur. Groups II, II+ and III are the industry standards now, along with some Group IV polyalphaolefin in the lightest grades.

Bob Olree, retired now from General Motors, takes a longer view of the LSPI issue, and pointed out to me, This phenomenon is not new. When the Chevrolet Corvair came out in 1960, some cars in the field developed a severe engine-knock problem on start up after deceleration. It was traced to the piston rings lining up, which resulted in oil being sucked into the combustion chamber on deceleration. The problem was solved by pinning the rings.

If you look closely at the cutaway Corvair Turbo in the lobby display area at the GM Powertrain Engineering building, you will observe that the rings are pinned, Olree went on. I dont know if it was technically pre-ignition or knock – but it was certainly noise caused by abnormal combustion, which in turn was caused by oil finding its way into the combustion chamber. And it occurred at low speed.

Bob added as an aside, Makes one wonder if oil droplets randomly being released into the combustion chamber was also the cause of wild ping, which occurred in high-compression engines of the 1960s.

Another note I especially enjoyed came from a reader who had worked with one of the same companies (Arco) as me during my checkered career, described in Octobers column recapping 50 years of change in the lubricants industry.

I have a friend who just purchased a 1935 Ford with a 37 Ford engine, wrote Charlie Ashley of Willis, Texas. The person he purchased the car from insisted he must use a non-detergent oil, but I seem to recall from my Sinclair days that we always told people that it was safe to go from the non-detergent oils to the detergent ones but to always change the oil filter when changing the oil. Charlie wondered what oil this antique car should use, and noted that his friend was adding ZDTP (the zinc, sulfur and phosphorus compound) to his fuel.

This query was particularly interesting since one of my former employers, Pennzoil, used to publish a list of lubricant recommendations for antique automobiles. As far as your friends car is concerned, if the engine is in good running condition, modern engine oils will work just fine, Charlie. Non-detergent oils were recommended back in the day because frankly, there werent any with detergent at that time. The only issue would be that a modern oil might cause some cleanup of the engine and seals, and result in some increased oil consumption.

I also think that changing the filter at every oil change is a good practice. As for adding ZDTP to the fuel, formulators have long used this antiwear agent as an oil additive, but I dont think Id ever heard of adding it to fuel.

Not every note I get is one that I can answer (imagine that!) and Arnold Frumin in Connecticut stumped me with this one: Steve, in years past my company sold a high-end, environmentally friendly lubricant to our distributor in Canada. He would sell this lubricant to the railroad industry in Canada and they would literally run the railroad cars through a lubricant bath. Have you ever heard of such a thing? Is there a name for the process? Do you have any info to share?

Baffled, I could only respond, Ive never heard of anything like this before but I suspect that the practice might be similar to deicing an airplane. If you can keep the ice off the bottom of the railcar and lubricate the wheels at the same time it would be of benefit. Just a guess on my part. I still dont know for sure, and if there are any railroad experts out there, feel free to chime in.

Some notes contain a lot of personal reminiscences. For Albert Frediani in Massachusetts, my March column on oil drain intervals brought to mind the old Pennzoil Answer Man column that ran for years. He wrote, I have always changed my own oil for the last 50 years. I worked in engineering and have always been curious about lubrication. Oil, what a wonderful substance. The best internal combustion engine wouldnt run a mile without it. Yet runs 300,000+ miles with it!

Then came the questions and observations: First, he noted, when you empty a bottle of conventional motor oil, there is a small amount of residue in the bottom, most noticeable in light-colored bottles such as Castrol white and Pennzoil yellow. I have not seen this in synthetic oils. What is this stuff? Am I better leaving this in the bottle? Is it an additive? Should I shake the bottle before I use it?

Answer: Thats most likely a bit of the detergent additive or filter aid that has separated from the oil. When detergents are made, they are over-based by a reaction to create calcium or magnesium carbonate. The over-base is there to neutralize acids formed in combustion that get past the rings as blowby and into the crankcase. Theres always water that is produced in the combustion process (the white smoke from your exhaust is water vapor), and it mixes with the acids to create some pretty nasty stuff. If it wasnt neutralized it would do some real damage in the engine, especially to the bearings. Synthetic engine oils typically have some ester or other additive to make the additive system more soluble in the base fluid, so it may be less likely that sediment will appear. I wouldnt bother to try to get the very last bit out of the container but it would be a good idea to shake well before using.

His next question: I buy oil on sale. I have an older Corvette I use very little on warm days. It has a non-roller cam. My concern is the reduction of ZDTP. About 20 years ago I purchased a lot of Pennzoil Synthetic SG oil. I have 24 quarts left that I plan to use. Should I be concerned? Is there a shelf life on unopened containers?

Answer: There really isnt a shelf life on oil although the sediment issue raised is a concern. Id pour out one of the quarts (shake well first) and see whats left behind. If it is no worse than what you see with current oils, go ahead and use it. Remember that SG oils dont have the level of performance that current oils do, so be sure to change it regularly. In addition, keep in mind that the API system of oil categories is backwards compatible. So an oil that is newer than SG (such as API SJ or SL) will lubricate older vehicles. That means you could use current oils and expect everything to work just fine.

Alberts final question: My Corvette owners manual calls for SAE 10W-40, SAE 10W-30, or SAE 20W-50. If I run out of the Pennzoil, I plan to use SAE 5W-30 synthetic with a container of STP. STP claims it is [compatible] with all oils and contains eight times as much ZDTP as a G2 oil. I figure this will yield approximately an SAE 10W-30 oil with sufficient ZDTP for my cam. Do you have an opinion about this?

Albert, as far as what viscosity grade to use with your Corvette, I think that SAE 10W-30 would be a good choice and I would not use any aftermarket additive mixed with it. The additive systems in oils are engineered to provide satisfactory performance without anything else being added. In fact, adding some aftermarket additives can actually degrade the oils performance. Stick with the straight stuff and save yourself some money.

Last but not least, I sometimes get notes that arent really related to lubricants but have a personal impact. A little over a year ago, I received a warm missive from Chuck Colyer, who for many decades was instrumental in engine oil development, working with the U.S. Army, Amoco and Lubrizol. He had been SAE president in 1983, a rare honor for an oil guy. For some time he had meant to thank me for my LubesnGreases articles, and at age 91, he quipped, I had better do it pronto.

Following World War II, Chuck continued, we thought we produced harmony between the oil and auto industry worldwide… Today, one classification doesnt satisfy all and we continue to strive for improved fuel economy, volatility, shear stability, etc. Who would ever have thought I would consider SAE 0W-20 grade?

Sadly, Chuck passed away shortly after he wrote to me. His contributions are worth remembering, and I highlighted them in my February column The Good Old Days. I got a very nice note back from his widow, Ginny Colyer, which made my day:

I am writing you to thank you for the article you wrote about my husband, the late Chuck Colyer. It brought tears to my eyes, as I remember the day he wrote to you. He was a faithful reader of your magazine and commented to me that he owed you many compliments for your writing skills in covering all aspects dealing with the oil and gas industry, as well as related industries. Again, his planning was on-time, it seems.