One reader, John Fischer of Illinois, asked if trucks produced before API FA-4 availability could adopt or switch over to FA-4, and in fact if any trucks going back to the 2010 model year could also adopt or switch over to FA-4. [To] continue to use FA-4 seems to be a given of course (if thats the factory fill), while adoption of FA-4 would be a specific change.

My response to John was, the fact that almost all OEMs (both on- and off-road) use SAE 10W-30 for factory fill is a testimony to their confidence in the viscosity of the oil being a non-problem. The difference here is that most factory-fill SAE 10W-30 oil has a high temperature high shear rate viscosity of 3.5 centipoise, minimum. SAE 10W-30 FA-4 oils are a minimum of 2.9 cP HTHS. Lower viscosity in the moving parts gives lower friction, lower emissions and better fuel economy. There are a lot of data out there which show that the lower HTHS viscosity is not a problem with regard to durability.

However, I should note that the American Petroleum Institute says FA-4 oils are specifically formulated for use in select high-speed four-stroke cycle diesel engines designed to meet 2017 model year on-highway greenhouse gas emission standards. So technically, by that definition, trucks made prior to the 2017 model year should not use FA-4 oils.

John came back with this comment, which is probably one of the end-user perceptions that will have to be dealt with: Im finally understanding that there are now going to be two SAE 10W-30 oils, one of which is a 10W-30 and one of which is not quite a 10W-30. At least I think that is how the man on the street is going to be seeing things.

My April column, Urban Legends, certainly gained the attention of a lot of readers. One of the topics that seems to be on most readers minds is oil consumption. Russell Sas of Montana described a situation in which he had seen a sudden increase in oil consumption. Russ drives a Jeep with a 4.0L straight-six engine, which was remanufactured. He broke it in on SAE 20W-20, then switched to SAE 10W-30 (three different brands). The last oil he used was a synthetic. In all cases, there was no oil consumption problem. With about 35,000 miles on the engine, he switched again to another synthetic, this time an SAE 5W-30. He drove about 1,400 miles and found that he had used a quart of the latest oil.

After several emails back and forth plus some additional information, such as the fact that Russ refers to himself as a spirited driver and that several other engines of his and others were seeing high oil consumption, we came to the conclusion that perhaps a heavier grade might be a better choice. I have been able to talk to others, including some OEMs who shared service bulletins showing that high-speed driving resulted in more oil consumption.

Dennis Beaver of California also reacted to the urban legends column with his note on the proper oil for his Cobra kit car. He was using a modified Ford Windsor 351W small-block engine, bored and stroked to 427 CID (cubic inches). The discussion here centered on the zinc content of an oil for flat tappets. After some exchanges on the proper oil and viscosity grade, as well as feedback from former General Motors engine guy Bob Olree (who passed away in October; see Page 54), we concluded that an API CJ-4 heavy-duty engine oil was the right choice to make sure phosphorus levels were high enough to deal with the potential wear, due to the cam and lifter architecture in his engine. Olree did point out that if a flat tappet engine is properly broken in, it should do just fine on API SN or ILSAC GF-5 oil, even with the lower phosphorus levels found in the most recent API category.

Another popular column was on the subject of new engine oils for old cars, back in May. It attracted so much attention that I was invited to chair a session at a Cadillac-LaSalle Classic Car Show! I wasnt able to make the meeting but found that others were also very interested, including an old friend from my Chevron Oronite days, Bob Freerks of Colorado. Bob concurred with the recommendation to use heavy-duty engine oil in older cars. He reported that his 5.2L Jeep engine had 220,000 miles on it and recommended HDMO for any car prior to a 2000 model year.

Another topic that came out of the Old Cars and New Oils column was mixing oils of different viscosity grades. Karl Braconier of New Hampshire has been involved in classic car restoration and was told by an old pro back in the 1960s that you could mix viscosity grades but not different brands. Certainly, its possible to mix grades and get something that is sort of in the middle, viscosity-wise.

Back in the 60s, before there were generally established oil quality levels (API ML/MM/MS notwithstanding), engine oils were likely different and quality was ill-defined. With the introduction of the API engine oil classification system in 1970 and later the API-managed ILSAC GF system in 1992, oil quality became more consistent and the mixing of brands was less likely to be a problem. Most oil marketers would frown upon brand mixing for obvious reasons. However, your oil analysis trends could be somewhat compromised.

I frequently hear from Al Frediani in Massachusetts. In one email this year, he inquired about the relationship between zinc and phosphorus content in engine oils. I explained that zinc dithiophosphate (the additive component used as antiwear, corrosion inhibitors and antioxidants) is manufactured by reacting phosphorus pentasulfide with specific alcohols to make a complex thiophosphoric acid.It is then neutralized with zinc oxide. If you calculate the zinc-to-phosphorus ratio according to the molecular weights of both, there are 94.7 parts phosphorus to every 100 parts zinc. For quality control purposes, zinc is easier to analyze, so that is what is controlled.The actual additive could have more or less phosphorus depending on the mix of components.

As far as the active wear-reducing component is concerned, its the phosphorus.There is also sulfur (thio) in the additive, which adds to the wear-protecting properties.

There were a number of questions about base oils, especially API Group III. Another regular correspondent, Blaine Ballentine of Iowa, asked whether API Group II and Group III base oils were really paraffinic or if there was still a certain level of naphthenics found in these oils. Its a good question, and after some back and forth, I was able to explain the processes by which both are made and assured him that the severe hydroprocessing that goes into making both grades virtually eliminates any naphthenic structures in the oil. In fact, that is part of the reason Group III has been defined as a synthetic.

Matt Thompson of Maryland was also interested in the relationship between volatility and Group II and Group III base oils used in heavy-duty engine oils. For most heavy-duty oils, about 75 percent of which are SAE 15W-40, volatility is not a major concern. They use base oils which are high enough in viscosity that their volatility is within the targeted API CJ-4 limits. Its 15 percent for 10W-30s, though. So, when we move to lighter-grade finished oils, base oil volatility becomes a potential problem.

Volatility is related to the molecular weight of various fractions within the base oil. In order to control volatility, it is necessary to remove more volatile components. That can only be done by taking material at the lower boiling range out of the base oil. When you do that, the viscosity goes up. In order to control viscosity, you must then remove some of the higher boiling range material.

The result is a very narrow cut with a lot of waste oil on each end of the boiling range. Refiners dont want to do that, since it reduces the final volume of product.

Summing up the years questions for 2017, I can say without a doubt that these were the most thoughtful and interesting Ive received to date. Keep them coming, because I become a better and more educated writer when you ask questions. On to 2018!

Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg@cox.net.