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pressure limits on synth oil

pressure limits on synth oil

pressure limits on synth oil

(OP)
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.

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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 . . .

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

"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.  

RE: pressure limits on synth oil


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.

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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).

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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!!      

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

(OP)
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.

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

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.

RE: pressure limits on synth oil

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

RE: pressure limits on synth oil

In my point that picking a 'best' one is complicated I by no means meant to imply that there were no significant differences, so perhaps I respectfully disagree with evelrod on this point: "it's the service interval that really determines how well the lubricant performs in any individual engine or application."

But service interval is part of the application; over the road trucks see much longer service intervals (and different service duty) than passenger cars.  That's why there are different API service categories.

If you have a particular application there are a number of ways a formulator can tune the performance for targeted benefits.  For example, the 1994 Nissan KA24E is known to be severe for valve train wear- that's why it is used for the Sequence IVA test.  If you use any API licensed oil you will get fit for purpose performance in this engine.  But for one that was used prmarily for short-trip, around town service it is quite possible that a motor oil with better valve train protection, maybe at the expense of high T deposit control, could very well translate into longer service life and/or lower maintenance.  

Changes in motor oil chemistry alone (i.e. without changing viscosity) can move engine output by +/- 3-5%, which can make one measurably 'better' for racing applications than another, even though drain intervals are usually short.

RE: pressure limits on synth oil

the reason for the perceived lack of performance may both lie in the amount of additves and in the baseoil itself.

in many "streetoils" nowadays the amount of metallic additives is reduced to meet emission criteria. they have however been replaced with other additives so antiwear performance should not really have been changed. although emiision criteria  have to be met, the actual performance tests by standardizing organizations or carmanufacturers have not been changed - so engine quality should not have diminished.

another reason migth however be the baseoil. the viscosity of a baseoil varies not only with temperature but also with pressure. the pressure variation usually is neglected, but in specific circumstances may well be important. in the valvetrain there can occur really high temporary pressures up to 10000 bar - which means that the oil locally temporarily can solidify. however, baseoils differ in their behaviour under pressure. it may well be that the particular synthetic oil has a smaller pressure coefficient then standard mineral baseoil and that may make a difference when high revving geartrains have to be lubricated. most synthetic base oils are poly-alfa-olefin based and the pressure coefficients of poly-alfa-olefins are usually smaller then those observed in mineral baseoils. that means that under high pressure conditions a simple "heavy" base oil may be better suited to the task then a "energy efficient" synthetic oil.

see for more information: http://www.iantaylor.org.uk/papers/friction.pdf

that file may take some time to load since it is about 7MB

RE: pressure limits on synth oil

I'd like to "resurrect" this thread (don't see one newer);  since the phase-out of ZDDP in Rotella and other diesel oils, the classic car world is in a tizzy trying to deal with this issue.  I know personally of 4 freshly rebuilt engines (all typical pushrod engines) that failed in less than 1,000 miles after careful initial break-in with cam lube, due to flattened lobes and lifters. All were running current spec, quality oils; some synthetic, some not. One of the British MG sites documented failure of the valve train on a classic engine within something like 50 hours;  some older Cadillac engines were toast in less time on another site.

My question is, why isn't ANYONE marketing legacy oils (made to older OEM specs)???  From what I'm seeing, every non-OHC engine in the country could be trash in a very short period of time!  While that may fit in with some people's agenda, it surely doesn't fit in with mine!

And no, I'm not interested in Royal Purple or Amsoil at $7/qt for a 40-yr-old car that is simply in too good a shape to throw away...

RE: pressure limits on synth oil

RossAB,

Interesting you mention this wear problem.  I have heard several times recently, and witnessed one case, of older pushrod engines with worn lobes and or destroyed lifters. All were using Synthetic oils.  The one i seen myself was a Small block chev, probably the most reliable auto engine in history!     I have recently built up a small block myself, And the maker of the camshaft states clearly DO NOT use synthetic oils.

Maybe time to look at Penrite oils again....




www.retallickeng.com.au

Was told it couldnt be done, so
i went and did it!

RE: pressure limits on synth oil

Well, Ross, since you brought it up...I am now at odds with all that I previously thought correct about synthetic street oils.  I just lost three cam lobes on my 1930 Model A engine using Mobil 1 after only 9000 miles !  This is the same engine that went 125,000 miles on 'who knows what quality' motor oils  (I'm only the second owner to drive this car.  However, the original owner died in '74 and I never got to meet him).   I'm going to pull it out and take it up to H & H for a professional 'look see', as soon as I can get it into my shop...Shops loaded with projects, mostly racing related...but, soon.  If I can remember (old guy syndrome), I'll post the results here.

Rod

RE: pressure limits on synth oil

I believe Mobil 1 is a SM oil which has the limited ZDDP. Could these be a cases where the lower ZDDP level causes the failure?  I'd try an oil that isn't API SM rated!  There are oils (usually higher viscosity's) without the SM rating!  A lot of work to see if a SM rated oil is the problem, isn't it?  I've read that GM sells a engine assembly oil additive that is supposed to get you though the break in??  I've also seen in "Skinned Knuckles"  rag Motorhead Hi-Z oil?? Claims to have 0.250 % Zinc and "the very best for flat tappet engines"?????  

RE: pressure limits on synth oil

BigMo,  that's my point, outside of the specialty mega-buck oils, no one I know of is selling anything but the most-current spec oil (i.e., very low ZDDP).  GM EOS is stated not to be used as an additive, only for break-in assembly lube.   Will look into Motorhead but as stated, I'm not interested in $7/qt oil for an engine that got along fine on dime-store Quaker State "back in the day"...

RE: pressure limits on synth oil

Pricing in the lubricant business is very sensitive to volume.   So now your obsolete dime-store oil is a specialty SKU.  Volumes are low, so it isn't worthwhile to a supermajor to fool with*, and the independents who want the business have to buy their base oil from the supermajor at undiscounted prices.  The technology is old but the additive companies have to get an attractive price for it to keep it alive- most have aggressively 'rationlized' their product lines to increase efficiencies/profits in the past 10 years.  So the independents aren't just trying to gouge you - at least not as bad as it may seem!  It's partly just the nature of the business.

If it's high phosphorus you're after then consider a universal service Diesel oil, since they don't have the same chemical limitations as the latest passenger car specs.  They're also cost effective because diesel oil is  even bigger business than passenger cars.  You may have to compromise on a 15W-40 vis grade instead of a 10W-40, but that shouldn't cause problems except in extreme cold service.

* indeed, the OEMs seek to limit distribution of 'obsolete' oils and thereby misapplication in vehicles that are still under warranty.  They maintain all categories up to current are back-serviceable, and so they are correct to do so.

RE: pressure limits on synth oil

drwebb,  I can understand the volume aspects, but I can't see that adding more than a buck a quart? As far as the market, how many flat-tappet engines are still out there?  I think GM and Ford went to roller lifters in the early 90's, and may still use flat lifters in some applications. Look at all the off-road (construction equipment) engines designed for higher ZDDP. I'm sure there are still many millions of vehicles that need the ZDDP.

Also, the newest diesel spec also reduced the antiwear additives due to the upcoming particulate traps and such for diesels.  It's apparently no better than the car grades now.

I see a fair amount of evidence that good ol' STP oil treatment may be all it takes, but the risk is really pretty high!

RE: pressure limits on synth oil

Does any one out there know what STP has in anyway??  Would be fun to know that.  It's an opportunity for STP to tell us and then sell to all those with old cars!!  Where can we get a cheap 4 ball test to compare oils??  I'm thinking that might be a good test for this problem??  

RE: pressure limits on synth oil

I've heard and seen on the web that it's ZDDP + EP-type additives.  They advertise on their bottles now that it contains the highest amounts of anti-wear additives.  It would be nice to see independent confirmation.

RE: pressure limits on synth oil

I thought it was mainly viscosity improver, aside from being mostly oil that is.

Regards

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

RE: pressure limits on synth oil

Oils and STP results from VOAs are updated on this site

http://www.lnengineering.com/oil.html
Follow up article from MG owners indicates that it is still not an issue in UK (SL oils)Penrite also released a tech bulletin warning about the use of SM oils with flat tappets
http://www.svmgcc.org/newsletters/apr_07rev3.pdf

Its odd that the SM tests include flat tappet testing but have not identified an issue.

RE: pressure limits on synth oil

KNap,  thanks for the post, there's some good empirical data there!  STP looks like a winner.

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