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.
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
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
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RE: pressure limits on synth oil
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
RE: pressure limits on synth oil
RE: pressure limits on synth oil
"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
Also: remember competition oils as mentioned have little to no detergent and more pressure additives.
RE: pressure limits on synth oil
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
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: pressure limits on synth oil
"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
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
"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
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
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
Amsoil is a good product.
Some of their sales methods are suspect at best.
Regards
eng-tips, by professional engineers for professional engineers
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RE: pressure limits on synth oil
RE: pressure limits on synth oil
RE: pressure limits on synth oil
RE: pressure limits on synth oil
RE: pressure limits on synth oil
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
Following patprimmer's message see:
http://thebestoil.com/tro.asp
RE: pressure limits on synth oil
h
RE: pressure limits on synth oil
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
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
htt
Amsoil have a tech bulletin on flat tappets
http://
These types of oils are a PAO ester mix, however with reference to M1 the ester content is low with AN being used.
RE: pressure limits on synth oil
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
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
Rod
RE: pressure limits on synth oil
RE: pressure limits on synth oil
RE: pressure limits on synth oil
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
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
RE: pressure limits on synth oil
RE: pressure limits on synth oil
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RE: pressure limits on synth oil
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