Synthetic oil

[Doug&Deb]

Engine rebuild is almost done. Any thoughts about using synthetic oil after break in period? The mechanics aren’t sure about the seals being up to the task even though they’re new.

[knuckleharley]

1 hour ago, Doug&Deb said:

Engine rebuild is almost done. Any thoughts about using synthetic oil after break in period? The mechanics aren’t sure about the seals being up to the task even though they’re new.

My best GUESS is synthetic oil wouldn't harm new seals in a newly rebuild engine,and if rebuilt properly,the engine should last practically forever.  Look at how long most of them lasted using crap oil like 30wt Quaker state non-detergent oil.

 

I am assuming you have a oil filter on the engine,or have added one?

 

I would be really hesitant to just add synthetic oil to a old engine full of non-detergent oil and crud,though.

 

 

Edited September 28, 2018 by knuckleharley

[Merle Coggins]

I've been running Amsoil in my truck for years. Yes, it has a couple of small oil leaks, but I don't believe it's any worse than if I used conventional oil.

[thebeebe5]

Synthetic oil won’t harm the seal.  What happens to older cars that are swapped to the detergents is that dino oil deposits are disolved away, and if a seal has shrunk with age and the deposits are dissolved and removed is that the seal begins to leak.  

 

I plan to swap to Amsoil after a couple thousand miles on my fresh 201 rebuild and I’ll have zero concerns about seal issues.  I’ll be using their “Z-Rod” 10W-30 weight oil to maintain adequate zinc for the flat tappet camshaft.  

[knuckleharley]

2 hours ago, thebeebe5 said:

Synthetic oil won’t harm the seal.  What happens to older cars that are swapped to the detergents is that dino oil deposits are disolved away, and if a seal has shrunk with age and the deposits are dissolved and removed is that the seal begins to leak.  

 

I plan to swap to Amsoil after a couple thousand miles on my fresh 201 rebuild and I’ll have zero concerns about seal issues.  I’ll be using their “Z-Rod” 10W-30 weight oil to maintain adequate zinc for the flat tappet camshaft.  

Any oil rated for diesel use has plenty of zinc in it.

[50 coupe]

i.e. Shell ROTELLA T, much less expensive than synthetic and will give all the protection you need for these old motors. 

[Don Coatney]

4 hours ago, thebeebe5 said:

” 10W-30 weight oil to maintain adequate zinc for the flat tappet camshaft.  

 

Why do you need zinc?

[austinsailor]

Oh, no! Not the zinc/no zinc battle again!!??

 

But, whichever side you are on, the "modern" diesel oils have most of the zinc gone. Rotella's current version, J, has little. But the older H version, which had plenty, is still made. It's sold for Detroit Diesels, which I've bought by the drum lately, and even in Walmart by the gallon, sold as older vehicle oil.

[knuckleharley]

59 minutes ago, austinsailor said:

Oh, no! Not the zinc/no zinc battle again!!??

 

But, whichever side you are on, the "modern" diesel oils have most of the zinc gone. Rotella's current version, J, has little. But the older H version, which had plenty, is still made. It's sold for Detroit Diesels, which I've bought by the drum lately, and even in Walmart by the gallon, sold as older vehicle oil.

I use Mobile 1 15-40 diesel in pretty much everything,including my 06 LBZ diesel.

Edited September 28, 2018 by knuckleharley

[Plymouthy Adams]

my oil is real, the car is synthetic  

[desoto1939]

If you are having the engine rebuilt fromteh ground up then make sure they use a good break-in oil when they are first starting the car engine.  When my engine was rebuilt i switch over to 10W40 oil and have run that for over 30 Years.  Also the properties of the newer oil has chnaged and i feel for the better.  If you wanted to add some syn blended oil that might help with the engine or maybe a qt of full synthtic oil.  Just my $1.00 worth of input.

 

Rich Hartung

Desoto1939@aol.com

[austinsailor]

For years I've heard that  synthetic oil can cause leaks in old motors because it's much slicker that petroleum  oil      and will slip through the seal.

 

i've also heard a new motor won't break in properly because of the same properties.

 

 

[Don Coatney]

6 minutes ago, austinsailor said:

For years I've heard that  synthetic oil can cause leaks in old motors because it's much slicker that petroleum  oil      and will slip through the seal.

 

i've also heard a new motor won't break in properly because of the same properties.

 

 

 

I agree. I have heard the same stories.

[Dodgeb4ya]

7 hours ago, knuckleharley said:

Any oil rated for diesel use has plenty of zinc in it.

That's not true these days ...

Edited September 29, 2018 by Dodgeb4ya

[DrDoctor]

   The reason synthetic oils will leak more in older engines, isn’t because of its “slickness”, but rather because of the size of the molecules in it, which are smaller than that of petroleum-based oils. The same holds true when comparing transmission fluids.

   As for the break-in issue, it’s not so much of an issue in contemporary engines, due to the advanced machining quality of the components within contemporary engines. In older engines that’ve been overhauled, with or without machining of internal components, it’s still an issue, as most machine shops/rebuilders/remanufactures don’t have the machining equipment with the requisite sophistication/computerization/tolerances of the EOM factories.

[belvedere]

7 hours ago, DrDoctor said:

   The reason synthetic oils will leak more in older engines, isn’t because of its “slickness”, but rather because of the size of the molecules in it, which are smaller than that of petroleum-based oils.

 Not quite...the molecules are just more uniform in size.  In a conventional oil, the molecules average out to a 10 (or whatever) weight, but in a true synthetic, they will be much more uniform.

 

This isn't even getting into the fact that many oils labeled "synthetic" in the US are actually group 3 oils, which are a very highly refined conventional.  Not that it's bad...group 3 oils can mimic true synthetics and provide excellent performance.  It's just that they aren't a true syn, such as group 4 (PAO) or group 5 (usually esters).  A bottle of finished motor oil usually contains base oil from at least 2 groups.

[DrDoctor]

   True – petroleum-based oils are produced by a refining process of the crude oil. Refining processes aren’t as precise as a manufacturing process such as utilized in synthetic oils. As such, the molecules in petroleum-based oils are randomly organized, and are of inconsistent size, and thereby inconsistent in their weight. The inconsistent sizes of these molecules negatively effects their ability to permeate certain media, as well as to pass between two close-fitting items, such as a part, and the seal’s surface against that part.

   Synthetic oils are manufactured under an extreme tightly controlled process, and can thus achieve a much finer pre-designed specific molecular structure that’s smaller that its petroleum oil-based counterpart, which yields a much more organized, and consistent, molecular size, and thereby a more consistent molecular weight.

   Further, one must take into consideration the viscosity index, which is the relationship between the base viscosity of the oil, and the temperature of the oil. Oils with a high viscosity index value aren’t affected by temperature as much than those with a low viscosity index value.

   The conclusion – the smaller, lighter, more consistent structure, of the molecules of a synthetic oil can pass thru a finer media easier than the molecules of petroleum-based oil. Thus. of the molecules of a synthetic oil can pass between an oil seal, and the part being sealed, easier than the molecules of petroleum-based oil.

[belvedere]

Well Doc, that was a very well-written post.  I was with you right up until your conclusion, when you threw in the "smaller, lighter" description!  Not sure where that came from!

 

Since the molecules of the syn oil are consistent, and the molecules of the conventional oil are less so (they just average out to the same size), some molecules of the conventional oil will necessarily smaller than those of the syn.

Edited October 1, 2018 by belvedere

[T120]

Several years ago my son brought home a high mileage PT cruiser ( bought it cheap)  and parked it in my driveway. Underneath the engine wasn't spotless, but there were no annoying oil drips on the concrete. He gave the car an oil change and for some reason used synthetic oil, right away the car started  marking the area where he parked it. After awhile I moved it, cleaned up the driveway and changed the oil using a multigrade 10W30 conventional oil and this solved the annoying drip...So from that experience I would guess that maybe there's a larger proportion of big molecules than the smaller molecules in conventional motor oil. ? 

  

[classiccarjack]

On 9/28/2018 at 4:26 PM, Don Coatney said:

 

Why do you need zinc?

It's very critical in the British cars.  When Zinc was reduced in engine oil, the neighboring shop next to mine began experiencing constant lifter failures and cam lobe failures. 

 

We got together and figured out the issue, as both our shops were the only shops that built engines in the complex.  I called Amsoil and the representative told me the news.  My neighbor began using STP oil treatment to supplement the Zinc deficiency.  From that day forward, not one more issue for him.  I began using ZDDPlus or ZDDMAX.  None of my Mopar Engines failed, but I heard of other makes having issues by others.

 

 

[50 coupe]

On 9/28/2018 at 6:03 PM, austinsailor said:

Oh, no! Not the zinc/no zinc battle again!!??

 

But, whichever side you are on, the "modern" diesel oils have most of the zinc gone. Rotella's current version, J, has little. But the older H version, which had plenty, is still made. It's sold for Detroit Diesels, which I've bought by the drum lately, and even in Walmart by the gallon, sold as older vehicle oil.

Regardless of of zinc content the 'diesel' rated oils should give ample protection whether in synthetic or dino. They are formulated to provide protection for diesel engines going thousands of miles more between oil changes then our cars would go and also handle the burdens of industrial diesel engines in the process. 

[DrDoctor]

Belvedere,

   You have a point concerning the seepage issue – the smaller molecules in the random-sized petroleum-based oils will pass by a seal easier than the consistent/uniformed molecules in synthetic oils. The larger-sized molecules within the petroleum won’t be able to get past the seal as easily. I guess it boils down to the volume of smaller molecules compared to the larger molecules in the petroleum-based oils. Given that comparison, one can’t definitely state that one type of oil will leak more than the other type, but rather – it’s dependent upon the ratio of small/large molecules in the oil in question, and the condition of the engine, and its seals. As such, you’re correct, and I stand corrected. I thank you for your cogent remarks, and for this civil discussion with you. With kindest regards . . .  

[kencombs]

IMO, formed after many, many, many years of working on engines and lots of study of oil info is this:

the need for zinc is driven by a combination of four things:

 

Valve spring rate.  Light springs are easy on wear,  The heavier they become the more demanding of oil.

 

Valve opening rate:  Some high performance cams have very rapid open and closing rates which really stress the cam/lifer interface.  That is what drove the development of roller based lifters and cam followers.

 

RPM,  The faster it turns the more wear per operating minute.  Newer engines normally have a much lower highway cruise RPM, but are capable of much more than our flatties.  My 5.7 Toyota cruises at less that 2k, but will shift a 6.5K if I make it.  I think it's electronically governed at 7k, but i don't intend to find out for sure.

 

Valve train weight.  Long push rods, big 'normal' steel valves, heavy rocker arms etc, require lots of push to overcome their inertia.  And, lots of spring pressure to reseat.

 

Our flatties have light springs, really slow opening and closing rates, aren't capable of really high rpm and have short light valve trains.

 

My '56 that's getting worked over for my pickup had mostly tar in the oil pan!!  Cam and crank fine. So, I'd feel OK with no added zinc, but use a high zinc oil.  belt and suspenders kind of guy

[DrDoctor]

 

   The “zinc” in motor oil is actually Zinc Dialkyl Dithiophosphate (“ZDDP”). The primary purpose for Its initial presence in motor oil was to protect the lobes of the camshaft, and the lifters running against those lobes. At high engine speeds, pressure builds up between the lobes and their lifters, causing pressure which can squeeze the motor oil out from these two mating parts. This created the need for an anti-wear additive. Hence, the introduction of zinc in the motor oil, because the molecules in the ZDDP bond to the metal surfaces inside of the engine, and thus create a “coating” that protects moving parts, especially the camshaft lobes, and their respective lifters. The introduction of roller lifters in high-performance racing engines reduced the rotational friction between the cam lobes, and the flat-bottoms of conventional solid, and/or hydraulic, lifters. Roller lifters have made their way into many contemporary engines, with correspondent reductions in internal friction, and thus increased efficiency, both in engine longevity (just one factor in that result), and fuel economy.

   As for the lubrication of the valve stems, while ZDDP does play a part in this, lead (tetraethyl lead) plays a more significant role in this. Lead was introduced into gasoline in the early 20^th century as an anti-knock additive, which also increased net horsepower of the engine. But, it also prevented the valves from micro-welding themselves to their valve seats. The eventual cure to this welding phenomenon was the introduction of hardened valve seats. That, along with improved metallurgy of the valves themselves, including the stems, and especially with lead’s incompatibility with the platinum media utilized in catalytic converters, has relegated lead out of contemporary fuels (with the exception of aviation fuels). It’s still available as a fuel additive, and it’s advisable to use it in pre-catalytic converter equipped cars, especially if one isn’t sure if the engine in that pre-catalytic converter equipped car has hardened valve seats. But, it should never be used in a vehicle equipped with a catalytic converter – it’ll ruin it rather quickly.

 

[Don Coatney]

4 hours ago, kencombs said:

 

Our flatties have light springs, really slow opening and closing rates, aren't capable of really high rpm and have short light valve trains.

That is exactly why I questioned using a high concentration of Zinc in a Mopar flathead engine.

4 hours ago, kencombs said:

 

 

3 hours ago, DrDoctor said:

 

   The “zinc” in motor oil is actually Zinc Dialkyl Dithiophosphate (“ZDDP”). The primary purpose for Its initial presence in motor oil was to protect the lobes of the camshaft, and the lifters running against those lobes. At high engine speeds, pressure builds up between the lobes and their lifters, causing pressure which can squeeze the motor oil out from these two mating parts. This created the need for an anti-wear additive. Hence, the introduction of zinc in the motor oil, because the molecules in the ZDDP bond to the metal surfaces inside of the engine, and thus create a “coating” that protects moving parts, especially the camshaft lobes, and their respective lifters. The introduction of roller lifters in high-performance racing engines reduced the rotational friction between the cam lobes, and the flat-bottoms of conventional solid, and/or hydraulic, lifters. Roller lifters have made their way into many contemporary engines, with correspondent reductions in internal friction, and thus increased efficiency, both in engine longevity (just one factor in that result), and fuel economy.

   As for the lubrication of the valve stems, while ZDDP does play a part in this, lead (tetraethyl lead) plays a more significant role in this. Lead was introduced into gasoline in the early 20^th century as an anti-knock additive, which also increased net horsepower of the engine. But, it also prevented the valves from micro-welding themselves to their valve seats. The eventual cure to this welding phenomenon was the introduction of hardened valve seats. That, along with improved metallurgy of the valves themselves, including the stems, and especially with lead’s incompatibility with the platinum media utilized in catalytic converters, has relegated lead out of contemporary fuels (with the exception of aviation fuels). It’s still available as a fuel additive, and it’s advisable to use it in pre-catalytic converter equipped cars, especially if one isn’t sure if the engine in that pre-catalytic converter equipped car has hardened valve seats. But, it should never be used in a vehicle equipped with a catalytic converter – it’ll ruin it rather quickly.

 

If this forum was geared towards high rpm racing engines with heavy valve springs and very lumpy cams then zinc or ZDDP might be required. But for a stock or lightly modified flathead six cylinder Mopar engine that spins at a low speed then no oil additives are required in my opinion.

3 hours ago, DrDoctor said: