pressure limits on synth oil

[rpmag]

In a conversation with two well respected race engine builders recently both independantly mentioned that they are not using synthetic oil in some of their race engines. These engines are DOHC of OHC 8v 4cyl race engines with quite high and fast lifting camshafts. Both builders reported premature wear of the cam and buckets/finger followers with synthetic oil and both are now using GP50 mineral oil with no adverse wear (all components from the same suppliers and were tested post wear and found to be within expected tolerances).
My question is: is there a point where the synthetic oil is less effective due to too great a pressure or is something else going on?
Engines were Alfa TC, Fiat TC and Ford Pinto. the fiat uses a 'bath' approach so that the cam and buckets are immersed in oil, so a reduction in oil availability due to increased drainage is not really a factor.

 

[patprimmer]

I would say that the synthetics tested contained less extreme pressure wear additive.

These have been reduced in some oils recently to reduce their tendency to damage to catalytic converters, but are still maintained at higher levels in some specific race only mineral oils.

I suspect some race only synthetics like Tawco might still retain higher levels of EP additive.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[evelrod]

Pat is spot on. The current crop of 'street' synthetics are looking to meeting the 'clean air' requirements and have consistantly been using lower and lower levels of EP additives (ZDDP). I have been using one of the prominant brands until recently switching to a race specific oil (RedLine) which does not need to meet 'street' requirements.
At $7.75 a qt. it's not cheap, but neither is one of my race engines. I have built and raced a DOHC Lotus twincams for over 40 years and have NEVER had a lubricant related failure using non synthetic oil...mostly Castrol 20W-50 which I still use for break in (I am looking into current formulations of Castrol, too). I use Shell Rotella T in my diesel truck and, as far as I can find, it has the highest levels of EP additive of any comercially available lube...It may end up being my "breakin oil"!

Rod

 

[rpmag]

Ah, thank you both. I now need to find an oil company who will publically agree so the information can be shared.

 

[drwebb]

Just to amplify, the consensus is that it is the lower ZDDP levels of the API SM service category that is the expected causal factor here and not the 'synthetic' versus 'conventional/mineral' basestocks. I'm sure this case will be added to the 'synthetics wreck engines' lore anyway though . . .

 

[sprintcar]

Try the guys at Royal Purple - they have synthetic street and race oils and might be able to shed some light on it from a Mfr perspective.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

 

[jayskind]

I don't know about fancy acronyms, but I do know that Zinc (an extreme pressure additive) has been reduced over the years in oil. Diesel engine designers who taugh me class claimed sythetics work well, but aren't worth the money for a diesel engine do to the build up of sulfuric acid in the crank case as a product of diesel combustion. I.E. no extension on intervals. Ney a decrease in wear upon testing in comparison with commercial oil. Getting back to gas engines, you look at the directions to any motorcycle owners manual: and they state to use no oil for automotive use. My Harley engine manual uses Harley360 50wt or get this engine oil designed for compression ignition engines in the 40-50 weight area as a last resort substitute. Despit having a peak power at only 7200rpms, what does that engine have in common with the engine you mentioned in your thread? Answer: due to design, the need for extreme pressure additives. Zinc and many other additive packages not available in normal gasoline engine oil, synthetic or mineral based. Adding packages available over the counter with particle rates smaller than the filter size has been shown to reduce wear on certain ball bearing crush tests I have seen.

Also: remember competition oils as mentioned have little to no detergent and more pressure additives.

 

[patprimmer]

I thought ZDDP was not as fancy as Zinc Dialky Dithio Phosphate, but each to their own.

It is not Zinc, it is a complex compound containing Zinc, the same as water is not oxygen nor hydrogen, but a compound of both.

The acid deal is critical, and ALL engine oils subject to blow by contamination are exposed to various acids. An additive is normally included to offset this and neutralise these acids. This produces what is known as the Total Base Number (or TBN if you want to be fancy). It can be added in various quantities, and is the main factor in determining oil life. Once TBN reaches zero, the oil will start to turn acid. This acid will attack the more vulnerable metals in the engine, which is normally the bearing materials as this is where the engine sees a lot of oil, the dimensions are critical and the temperatures are high.

To quote a Castrol add that used to run here, "Oils ain't oils Sol"

There are several types of synthetic oil bases. These are distinctly different chemical types. I can't be bothered researching this again to determine details.

Synthetic oils tend to be naturally detergent, so you do not need to replace as much of the slippery stuff with detergent.

Synthetic oils tend to retain a more consistent viscosity over a wider temperature range. In mineral oils, the additives to create multi grade oils can be in there in quantities that approach the amount of slippery stuff. Viscosity improver's are not lubricants as such, and the fact that synthetic oils need less of this can have 2 results. One is that there is more room in the package for more actual oil or slippery stuff. The second is that you can cover a wider temperature range with the same amount of viscosity improver when compared to mineral oil.

Synthetic oils tend to be more resistant to oxidation (the effect on oil exposed to heat and air). They can either have less antioxidant in them, or they can last longer at higher temperatures for the same level of degradation of the base oil.

In my experience, synthetic oils tend to cling to a surface longer. My very unscientific test for this was that old engine parts were stored in a cupboard for several years. I noticed some were so slippery I tended to drop them unless I consciously increased my grip. On investigation, the slippery ones always came from engines I knew were last run on synthetic oil, those oils being Mobil 1 20W50 or AMS Oil racing 20W50.

Graphite has been known to be a lubricant for centuries, but no respected oil company uses it in engine oils.

PTFE (or Teflon or Poly Tetra Fluro Ethylene) has been around for decades and at least some of the people who make it DO NOT recommend it as an engine oil additive, despite the fact that it represents a large and profitable sales potential for them. When it is burnt, one of the by products of combustion is hydrofluoric acid. This acid is so strong that it is used to etch glass.

Molybdenum Disulfide has also been known for some time and has very good EP properties and anti seize properties. Whenever I have seen it added to an engine, the filter was very heavy if changed shortly after adding the molly.





Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[drwebb]

"Synthetic oils tend to be naturally detergent" - half true. Esters (GV base oils) are polar and so have good solvency. PAOs (GIV base oils) and deep hydrotreated stocks (GIII base oils) are actually defensive on solvency to conventional mineral oils (GI and GII base stocks) due to the lack of aromatic components. So motor oil detergency properties depend on the formulation and are not automatically determined by the class they are marketed to.

"In mineral oils, the additives to create multi grade oils can be in there in quantities that approach the amount of slippery stuff" - A typical mineral 4T motor oil will contain 5-10% performance additives (detergents/dispersants, antioxidants, antiwear agents, corrosion inhibitors, PPDs, antifoam and friction modifiers) and 5-15% viscosity index improvers, leaving 75-85% base oils. It is true that synthetic base stocks, with their higher native VI's require less VI improver than GIs and GIIs for the same multigrade spread, and several synthetic products are out there that achieve modest multigrade requirements yet apparently contain no VI improvers.

And ZDDPs are generally considered antiwear additives and have traditionally been used to deliver phosphorus to protect cams in valve trains. Extreme pressure agents usually deliver sulfur and are most useful under the high-load and low sliding speeds of hypoid gear systems. While there is no formal distinction between and EP and AW agent, the terms are typically used to describe different lubrication requirements that are addressed with different chemistries.

To set the record straight there are no limitations on the content of zinc in passenger car motor oils. The API SM spec requires phosphorus between 0.065 and 0.085%, which as patprimmer alludes affects the zinc content since that's how the P is typically delivered, but the fact is that one can have as much zinc as you want in the oil.

 

[25362]

If I may add to what drwebb has said, anti-wear refers in general to the prevention of damage caused by moderate and intermittent loadings, whereas EP means protection from shock loadings aand continually applied heavy or sliding loads.

Another possible difference could be found in that ZDDP is ash-containing vs "ashless" sulfur and phosphorous alternative chemistries.

 

[sprintcar]

Regarding the Harley oil - unless this is an early engine, the bottom end has roller bearings. The EVO generation can run on synthetics (Harley now has one) and 20w50 seems to be about right. I tested mine on 10w40 and 10w30 synthetics but found the lighter oils made the engine noisy. Also found that the synthetics ran about 25 deg F cooler than HD mineral oil.
Harley's original 20w50 formula (circa 1980s') was based on the old Sunoco CAM II race oil with zinc added for the air cooled engine.

"If A equals success, then the formula is: A = X + Y + Z, X is work. Y is play. Z is keep your mouth shut."
-- by Albert Einstein

 

[Metalguy]

Rod,
"I use Shell Rotella T in my diesel truck and, as far as I can find, it has the highest levels of EP additive of any comercially available lube...It may end up being my "breakin oil"!"

I've been wondering how Rotella T 15-40 would work in car/motorcycle gas engines-not just for breakin. I've got a BBC truck engine that uses a bunch of oil (2 morons involved here. The clown who bored my cylinders too big [.006" clearance] and me for thinking I might get away with it).

 

[evelrod]

Shucks, I AM famaliar with the problem. I fixed mine with a new set of pistons...a race engine from one of the 'leading east coast race engine builders'---yeah, RIGHT!

Try Torco 70......just kidding. I still using Castrol 20W-50 for the time being for break in. I use it for warm up, adjustments and a few pulls on the dyno then drain it out and replace it with synthetic. The Dodge is the only thing I own now that still uses conventional oil...after 200,000 miles, why change now?

I used Shell in my BBC motorhome once when it was all I had for it's 'yearly' oil change...seemed to be ok. It's back on Mobil 1 now.

Rod

 

[bigmo460]

I read that to use the API star ( found on the side of the oil container) the oil has to have less than 1000ppm of phosphorous. Phosphorous and Zinc are in the ZDDP, which boost the anti-wear properties of the oil. As I understand it they go together in order to get the anti-ware properties? This is done to limit phosphorous, thought to damage catalytic converters. This means oils with out the seal dont need to limit. As I also understand, only oils with 10w30 viscosity or less need to comply to this standard. So oils with higher viscosities can have higher ZDDP. I'm getting my information from themotoroilsite.com
This site seems to have done a good job of researching various oils and rates something like 800 plus oils in the Appendix? The appendix has tabulated 12 specifications for each oil, many of which are ASTM test results. It suggests that Amsoil is best? Do any of you have any experience with this product? I'm tending to believe this and therefore wouldnt use any other product in my engines!!

 

[patprimmer]

Many Amsoil salesmen have been banned from this site for pretending to ask or answer questions while directing members to Amsoil sponsored promotional sites.

Amsoil is a good product.

Some of their sales methods are suspect at best.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[rpmag]

WRT the quality of the site and the information on it, I would also take into account Pat's point. I would like to know the background of the site and any (if any) commercial arrangements they might have.

 

[rpmag]

with a little further digging it turns out that the forum owner is an Amsoil dealer who wrote the motor oil bible.

 

[bigmo460]

I assure you I'm not a dealer but would like to use the best oil for my engines. Thanks for the feed back. Are there any other sources for whats the best oil? I have some experience with Mobil 1. We (OEM) dyno. tested it in our turbo engines in the past and it was far better than Std. oil. We found at that time it's main benefit was not coking and less wear in the Turbo housing.

 

[drwebb]

Picking a "best" oil is almost like defining the "best" wine. If you looked at the full raw results for the Sequence Engine tests (rather than simple bench screeners that only simulate narrow performance properties, as is usually done by oil marketers), you would see that there are like 27 categories that must be passed and there is not one product that beats all comers in all categories. For example, the Sequence IIIG might show oil A with lower piston top deposits and oil B with better ring land cleanliness. So which is better? With an API licensed product you know they both met the minimum standard, but that's all.

 

[evelrod]

I think I heard this on the forum once or twice...Just about any motor oil you can buy over the counter today is far superior to the very best racing oil of the 60's, 70's, 80's, etc., with few exceptions. In my opinion, it's the service interval that really determines how well the lubricant performs in any individual engine or application.
Drwebb has it right, as long as the bottle has that API seal you are assured that the oil meets the min requirements and, in 99.99% of the time (given proper service at timely intervals) will perform within specs.

Since my last post, I have just given up on Mobil 1 and have gone back to petro based everything
except race engines (Redline) and my Model A (still have enough older Mobil 1 on hand for it's next few years use).

Rod