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.

 

[25362]

Following patprimmer's message see:

http://thebestoil.com/tro.asp

 

[Knap]

Perhaps indicates not a base oil issue

http://www.machinerylubrication.com/article_detail.asp?articleid=586&relatedbookgroup=Lubrication

 

[drwebb]

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.

 

[romke]

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

 

[Knap]

The concern appears to be over ZDDP rather than base oil

http://www.joegibbsracingoil.com/datasheets/81106.php

Amsoil have a tech bulletin on flat tappets

http://www.amsoil.com/dealer/techservicesbulletin/TSB_flat_tappet_and_camshaft_lube.pdf

These types of oils are a PAO ester mix, however with reference to M1 the ester content is low with AN being used.

 

[RossABQ]

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...

 

[kenre]

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....

http://www.retallickeng.com.au

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

 

[evelrod]

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

 

[bigmo460]

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"?????

 

[RossABQ]

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"...

 

[drwebb]

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.

 

[RossABQ]

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!

 

[bigmo460]

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??

 

[RossABQ]

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.

 

[patprimmer]

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

Regards

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[Knap]

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.

 

[RossABQ]

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