It was a while I settled on my oil choice but from memory the problem I found with trying to find a suitable 0w or 5w oil is that they are mostly...modern, designed for modern engines.
So are designed with considerations that don't matter or could even be detrimental to an old engine like a Jaguar v12, that doesn't have cats, or EGR, or hydraulic tappets, or direct injection or particulate filters etc etc etc.
Also again from memory, i'm sure I read it's more difficult for an oil to perform well & remain stable and long lasting, the wider the difference between the numbers. So say a 5w30 is more stable than an 0w50.

But I was also nervous about using a more boutique or specialist/no-name oil for reasons in the thread - money for testing etc. & again I was nervous about specialist 'classic' oils form the likes of Castrol e.g their 20w50, as I got the impression they are intended for...proper classics, like cast iron Carb engines from the 1950s, perhaps more designed for high fuel dilution, or very low miles between changes etc.

Also with a side-eye on cost, & what I could find actually for sale... is basically a summary of what lead me to choosing shell Helix HX7 10w40.
I wish it was just more straight forward and there was just an agreed 'best oil' but unfortunately I think there isn't.

 

Most of us have an owners manual in their glove box, i will trust that. There are multiple weights listed, just stick to one of these and never think about it again lol.

 

When I hear "longevity" and "Jaguar V12" the first thing I think of is "cooling system"

Anyhow, how does a Jaguar hobbyist measure wear and longevity? I reckon sending your old oil out for analysis might be useful in that regard?

It would be interesting to turn back the hands of time and take 5 brand new Jag V12s, each on a diet of a different engine oil, run each of them identically for 200k miles, and then do a full engine teardown for inspection and measurement of wear. I wonder what we would learn and how useful that knowledge would be, in a real world sense, today. Speaking for myself it isn't that important to me whether I need an engine overhaul at 200k miles versus 220k miles. But that difference is probably very meaningful to a guy owning 100 taxi cabs who is trying to control operating expenses.

What would be truly useful, IMO, is identifying which engine oils actually harm the engine. I don't mean some increased wear over 100k-150k miles of use. But actual immediate harm.

So, which motor oil brands or types are so bad or so incorrect that we should avoid them like the plague?

Cheers
DD

 

Any that aren't changed frequently enough and backed up by an appropriate filter, change frequency must be based on how the car is used and the type of oil you put in it - the old style mineral oils degrade faster than modern synthetics even when the car isn't used they're degrading (not so much the synthetics), filters are another can of worms - not all filters are equal.

The biggest killer of a V12 is poor maintenance, neglect and inappropriate driving, treat them right and they're pretty bullet proof - that means no 10 minute trips to the store, if you aren't prepared to redline it occasionally the V12 will hate you (true of any engine though - the higher the performance the more it needs to be exercised), no leaving it for months without stretching its legs - personally I would avoid the antique mineral oils like the plague now, 100% synthetic, preferrably one with an Ester base is all I will use in any of my cars (and I have a few) - for what it is worth it is a habit I got into when I had a track day habit and had oil analysed - I don't do that no more .... but the metals and contaminents were lower with an esther based, on track days I ran a heavier oil than you would a daily driver (10W 60) because it gets hot, real hot, and crazy thin - like no oil pressure on tickover thin ... .

I drop the oil and replace every year regardless in all my cars, I never let a car pass 6k miles but I try to assess how long it has sat in traffic - I just wish there were hour counters same as commercial machinery - but there ain't. Cost of even the most expensive oil is insignificant compared to the alternative.

Mine went down not because of the engine but because of the tin worm (corrosion) - but it will be back with a vengence next year (though I said that last year and this year) ...

 

I would agree. There is no oil that is so good that it will protect the engine from neglect. But that's not what I was asking.

I was asking which oils are so bad that they will cause engine damage. Not fractional percentage of increased wear over the course of 150k-200k miles. Actual damage.

If we can identify those oils then we've really hit upon some useful information.



I would ask the same question. Which are so bad that they should be avoided at all cost for fear of something really awful happening?



I would agree. And it's typically neglect in the cooling system that kills 'em off.

When is the last time any of us heard of a failure of the reciprocating assembly in a Jag V12? I'm not sure I've ever heard of one !


I certainly agree.

Until the body became too rusty I used my V12 as a daily driver for several years. My daily work commute was a grand total of 4.6 miles! I never had any reason to believe the engine was being harmed in any measurable way but it did require the Italian tune-up fairly often. And I was only too happy to oblige . When I sent the old girl off to the the boneyard the engine was still running like a watch!

Cheers
DD

 

The so called classic oils are a cheap group1 base oil with lots of viscosity improver added, and they shear out of grade fairly quickly. In the oil world these would be considered like the "Value range" house brand products at the supermarket - not high quality and you can get better oil buying the conventional oil from a major oil company.

 

Forgive me, but the one thing I’ve come to believe in the XJS V12 after reading the forums for over 30 years is it could run on bacon fat and be just fine. I don’t recall a single oil related failure that wasn’t caused by something else.

Jaguar was awesome at times with brute force engineering, and the V12 is a master class in that as far as oil volume, galleries size, etc. Plus the numerous little leaks are nice rust prevention (or at least I tell myself that)…

 

Diesel oil that isn't dual rated for gasoline service for example, or a gasoline oil rated less than about SF, unless used strictly for break-in purposes with a short drain interval.

When I was working for a company that built oilfield equipment we bought in engines mainly from Caterpillar and Waukesha and these were functionally long blocks, ranging from 95hp to about 5,500hp. We had to design and built the starting, oil, cooling, exhaust, fuel, electronic control, mounting and coupling systems. I've been to many of the courses the engine OEM's offer for engineers who need to "package" these engines. These engines ran on natural gas, as they were used for compressors that pump natural gas in remote locations, so the engines burn what they pump.

We sold a unit with a Cat engine to a major oil company that had a policy to only use their own lubricants. The problem was they made engine oils rated for diesel service and gasoline service, but not one rated for natural gas. So they used a gasoline rated oil of the recommended viscosity. Once commissioned, the engine made it about halfway to the first recommended oil change interval before it seized up due to lubrication failure from the oil being incorrect. Not only was that a $2 million "oops" for a replacement engine, the bigger problem for the company was the waiting time to get a new engine at the time was about a year and a half. Using the wrong oil cost them a lot of money.

 

According to the triboligist on the small saloon forum, If you want a Quality level to follow, once run in, use any product APPROVED against Mercedes Benz 229.5. (NOT meets the requirements of). They physically test each candidate oil prior to approval and have an arduous test regime. Many products to choose from. The approved is important!

https://operatingfluids.mercedes-ben...sheet/229.5/en

 

Filters are yet another can of worms, the things to look for you cannot see - the particulate size that they can capture, the lift pressure of the bypass inside them. A filter needs to be capturing 30 microns or less, problem with such a restriction is that improper design can lead to the internal bypass lifting (all oil filters should have this), if the bypass opens unfiltered oil is going around the system. I stick to the Jaguar branded filter but is it the best - I doubt it given my experience with aftermarket parts - so my plan is to change it frequently. I use this link only as a starter so that the technology of filters and how they work is clearer - there is more to them than many realise.


I would challenge the Jaguar are best re oil galleries etc having given mine considerable attention during the rebuild, the supply to the heads is particularly poor, the oil pickup strategy is a joke (once primed it is fine providing it stays primed, the oil cooling strategy is a disaster and creates a sediment trap in the oil cooler which is an absolute bear to get at / remove.

The cooling system is an absolute abomination and is one aspect to my V12 that I have 're-designed' I won't go into crazy detail here. Worst thing you can do is follow Jaguars recommendations - Barr's leaks every coolant change !! (hell no don't do it) - and never never never use straight water or water from the tap (not a Jag recommendation but I know many use straight water with no 'anti corrosion / anti freeze' properties. You don't need a cooling system filter ever if you use the correct 'stuff', you absolutely must make sure the engine grounds are good (I added additional straps) because not all corrosion is caused by O2 but the establishment of an electrical circuit between differential metals, then there is the pitting on liners caused by cavitation if the specific gravity of the coolant is too low - what is the best antifreeze / anti corrosive - hells bells there are those worms again - I used good old 'blue' glycol but once I light it up I don't know what I'm going to fill it with - I have been looking into OAT technology.

On the Mercedes specs - beware - they are forced to incorporate requirements for fuel efficiency, they also do so against the tolerances within their cars - the oil spec isn't necessarily a good indicator but how do 'we' prove that what it says on the label is accurate ... though I do agree with this to some extent how do you prove any of it. It is interesting that the oils that I stick to are in the Mercedes list - Fuchs Titan and Castrol Edge, I have used Shell Helix too when I ran the Sprinter but the Castrol and Shell I reserve for the 'daily drivers' - 2 * VW Passat Est, my Audi S4 gets the Fuch's

 

Thank you.

Cheers
DD

 

I agree....although perhaps for different reasons

What driving/owner/maintenance conditions would create this scenario?



I haven't looked at oil filter tests in many years but one of the problems was that oil filter manufacturers don't make all of their filters to the same quality or design standard so shopping by brand name alone doesn't guarantee you'll be getting what you think you're getting.

Add to that the problem of label engineering....which does take place with filters. Do we really know what we're buying?

Which, IMO, is the most effective, and virtually foolproof, plan for 99% of us.....to the extent that the tons of information at our disposal becomes pretty much academic.



I'll say. There are aspects of it that I still can't quite wrap my head around. We are fortunate that, nowadays, thanks to the internet, we have more understanding and knowledge of the oddball cooling system than we had decades ago. It's easier than ever.....though perhaps not outright easy..... to make the system work properly.

Owner paranoia became part of the problem, IMO. But that's a different conversation.

Cheers
DD

 

Inadequate oil changes, inappropriate oil grade selection for the environment / temperatures particularly when engine is cold - excessive differential pressure across the filter which is compounded by the flow rate that the V12 oil pump can achieve - I have yet to see one that lists the lift off pressure of the internal bypass.

As for the knowledge like all things engineering and in particular fluids engineering has come a long way since the 70's - like it or not decisions made 40 years ago were based on the knowledge and technology available at the time, does that mean that choices need to exclude advances in engineering ? - I am not of that opinion which is why I no longer have a rats nest of vacuum lines / valves or even a distributor - but that's a story for another day.

 

Which, IMO, simply comes down to changing your oil and filter a regular intervals and being sensible in choosing what grade to use.


I am 100% 'for' including advances in technology....if doing so enhances your ownership experience. And I'm 100% 'for' making the advances part of the discussion.

What I'm trying to do, here and in countless other threads over many years, is balance the discussion, to somewhat demystify the Jaguar ownership experience. This is not not intended to be adversarial although I understand that it might be perceived as such.

What I've discovered over the last 28 years, owning several Jags as daily drivers, is that they're not quite as exotic and mysterious and problematic as legend would have it. A legend that I myself once believed in. They're great hobby cars that a decent DIY hobbyist can enjoy without as much work or worry as many believe. They can indeed be reliable. The work needed is usually well within the realm of the average enthusiast. They don't require an unusual diet nor reengineering of the various subsystems.....although either or both can obviously enhance the experience for some.

My knowledge and understanding of technology, science, and engineering is virtually nil but that hasn't prevented me from years of Jaguar enjoyment. Not should it prevent anyone else, IMO. I'd like to see more old Jaguars enjoyed by more hobbyists. For that reason I'll be the guy who presents the "It's not quite as difficult or complex as you think" side oft the story .

Cheers
DD

 

And if my responses are making you think that I am responding to perceived confrontation that is not the case so if that is how it comes across that is not the intent.

All that I seek to do is to put some sources of information out there not based on internet myth, more to support the decision making, to be informed not misguided, I find that many are too ready to believe anything the internet puts in front of them - so I seek to shut down internet 'myth' or at least get others to challenge what they read.

 

As the cooling system has been mentioned, and apologies for the change of subject, but I thought it worth mentioning that it can be made to function like a 'normal one', if you have a non ABS car. However, since Ben said in Post 50 above "The cooling system is an absolute abomination and is one aspect to my V12 that I have 're-designed' I won't go into crazy detail here." But i will about what I did Ben!

I agree the OEM cooling circuit in the XJS V12 is an abomination. In a pre facelift, non-ABS V12 XJS it can be sorted to be much better. The problem, fundamentally, is the extraction of air from the cooling system, and this is a problem because the header tank is below the level of the engine and the radiator: hence the desperate air bleed/banjo/central filler spout/force-fed venturi/radtop pipe/question mark pipe "system" to overcome this fundamental flaw.
The fixing design (explained to me by Grant Francis who did it first, and which I developed and installed in my car) is as follows:

1. Move windscreen washer bottle to the space behind the wing stone baffle. The problem for an ABS car this original washer bottle space is not available as it is full of ABS stuff, which is why Jaguar moved the washer reservoir to the wing on ABS cars)
2. Have a header tank made up with three outlets: i) 1/2 inch diameter at the bottom to tap into the heater return pipe, ii) 5mm into the pressured part near the top for the radiator bleed, iii) overflow to atmosperic tank in the cap space as normal
3. Iemove the banjo, radtop crosspipe, question mark pipe, OEM header tank, venturi high pressure source pipe, and the spouted crosspipe and all associated smalllbore flexibles, (blank off as required
4. Install the saloon spoutless crosspipe to the engine
5. The thread size on the radiator bleed bungs is 1/8 inch BSPP. take the bung normally on the LHS and install it into the RHS (old banjo) radiatot position.
6. Buy a SHORT 1/8 BSPP 90° bend and a 6mm hosetail to fit. Install this in the LHS of the radiator
7. Run a hose/hose and stainless 4mm ID (6mm OD) from this hosetail to the header tank you have installed in place of the washer bottle
8. T into the heater return pipe from the 1/2 inch outlet on your header tank
9. Run the overflow to a atmo tank installed where the OEM header tank used to be.
10. Fill system from ABOVE the level of the engine/radiator! Kiss goodbye to all your fill and bleed problems!

Custom header tank: blue hose goes to the heater return (this is the main connection to the systyem to fill it). Small hardline to red flexible is the bleed line from the radiator. Longer red flexible is to the atmospheric overflow


View from the rear looking forward. Filler for wing mounted washer bottle by the tank.


Close up of connection to the heater return. I used very high spec hose for this connection and double T clamps.


Overall shot of the system. You can see the stainless 4mm ID hardline going slightly uphill from the radiator to the tank. The red tank is the atmospheric overflow. NOTICE: no central filler spout


Solid bung on RHS where the banjo used to be


90° 1/8 BSPP fitting to bleed the air to the header tank


My radiator top fixings. The rearmost holds the electric fans and the front one secures the radiator, the aircon dryer and condenser top fixings. Loads more airflow through the engine bay. No foams round the radiator either.

 

I dumped the atmospheric and had a larger 'shaped' expansion tank made, my original was round but I determined the capacity was too small to manage the expansion, retained the bleed circuit, my washer bottle is behind the right headlight and the vacuum reservoir behind the left (retained only because of the Delanair but I plan to work on that too - eventually - eliminating any dependence on vacuum for anything but brake servo). I have a 4 row radiator, larger fans and three temperature measuring locations - but this is way off topic -

I'd love to find a solution for the oil cooler but locating one given the design of the circuit is more of a challenge than I am interested in right now the fact that you cannot drain the thing or the pipes under the engine is a real annoyance.

 

That's why I gave the list from MB - they are the ones approving the oil and if it's on their list, it has been tested by them and passed the tests. The difference between "approved" and "recommended" is that an approved oil has been tested and passed the tests. A recommended oil has not. It might pass if it was subjected to the tests, or it might not, you don't know.

The 229.5 spec is a quality spec and it is only for gasoline rated oil. It's is things like staying in grade, resisting oxidation and nitration, and appropriate TAN and TBN that will stay in spec for the expected drain interval, not etching bearings, etc. It isn't a viscosity level which might be specified for fuel efficiency. Any viscosity could meet the requirements of the spec if it was designed to do so.

Oils meeting this spec is generally considered to be among the highest quality oils on the market for passenger cars.

 

As the thread owner and the person who opened the floodgates to the variety of differing opinions on this topic, I guess I must take the accountability for any tensions that could arise!

However, it's been great to see the politeness with which members have read and responded to the often differing views, perhaps reflecting the respect with which we all have for other owners and our common enjoyment of our Jaguars.

I've very much enjoyed reading the various posts and have a better appreciation for the nuances of oil viscosity, understanding better the reasons for the original Jaguar recommendations in the handbook, the advances in oil technology, and why we might now consider a differing approach with modern oil technology. As a result, I've not only made my choice as to the oil I'll use for my friends 6 litre, it's also made me consider changes to the regime I'll use for my other cars.

I'm also grateful to Doug for morphing the conversation to thoughts about the oils and grades we might wish to avoid that could negatively impact the health of these otherwise robust V12 engines. And thanks to Ben, Craig & Greg, amongst others for their reponses to Doug's prompt.

We all have slightly different approaches to ownership and maintenance of our cats, reflecting our personalities, use of our cars, and our technical capabilities. My mantra has always been change the fluids regularly - engine oil, gearbox, diff, brake fluid, coolant, PAS etc. Fluid is cheap, components can be very expensive.

Thank you all for your input, I'm hugely enjoying the debate and feel better informed. Oil viscosity is my new pet subject!

Cheers

Paul

PS And I still only put 97/98 RON petrol with max E5 content in the cars. Light blue touchpaper and retire......

 

Très diplomatique, très juste, très amusant, Paul. Un grande "merci" pour votre Présidence.