Box answered your question in better detail than I could have.

Most folks think an engine only gets to the temperature that the coolant is at.

Also note that pressure itself creates heat, there are parts of this engine under much higher forces. So shear strength of oil also becomes a factor.

 

Here are 2 good article about the carbon buildup problem and its link to engine oil.

Fortunately we have been spared for the most part, but we are not immune.

So with good oil habits we delay the problem even further.

5 Q&A's: Intake Valve Carbon Build-up, Direct Injection & Mini Coopers

Intake Valve Deposits in Gasoline Direct Injection Engines

 

I'm aware of the internal forces as well as the high temps realized within ICE's, where I disagree is that IF in fact said oils are compromised that that fact would not show up with the various labs do their analysis. These oil samples, examined under pretty strict scientific tests, have shown little to no degradation/breakdown/or excessive contaminates which could in any way cause or let damage happen to our beloved cars. This has shown to be the case in every single test I've seen which seems to conclude that changing oil sooner than recommended intervals has shown zero returns in terms of protecting your car any more

 

You're trying to argue Apples vs. Oranges. Again, your dismissing the obvious.

 

I purchased my 2010 XK 2.5 years ago with 4,800 miles. The oil was clean and I had it changed with the brake fluid at 6,000 miles. Now I have 8,500 miles. Am I suggested to change the oil (Jaguar synthetic) because of time? I don't think so as synthetic doesn't break down as conventional oil does. I'm sitting quietly and doing nothing as I want to find any excuse to keep my car out of the service dept to avoid any damage or mishaps which do occur. My opinion.

 

Time is one of those factors in which acids take their toll. This is the byproduct of the combustion process that enter into the crankcase. Short trips make the condition worse, where an engine doesn't achieve full operating temp, and rich mixtures contribute.

 

Hey Rob, maybe the dealer thinks that WA is a harsher environment. Over here on the Gold Coast we have it done annually for the XKR.

 

Hi Bruce,
I called the national number without giving my location, so that wasn't it.
On balance, I'm inclined to leave it. I'll have a discussion with the guy who does my car as well - he is both the owner of a Jag/Rangie specialist garage and my friend & neighbour, so I'll be interested in his views of everyone else's views!
Cheers,
Rob

 

I have S-Type maintenance sheets including for Arduous. (There was no Severe set when I got them.) The sheets include 2.5, 3.0, 4.0, 4.2 NA & SC, diesel so I suppose somewhat include engines in XK cars.

Mainly Arduous seems somewhat intuitive, includes places like Afghanistan, and things like:
Frequent driving at high speeds in high ambient temperatures above 50ºC
Frequent driving in severe cold weather below -40ºC

I think people should do whatever they like and whenever they like as regards oil changes etc. Treat USA as Arduous renamed to/from Severe if you like.

Someone posted oil analysis results for quite a few years of the 4.x (I forget 4.0 or 4.2) in the S-Type section, changed at the Jaguar 12 month / 10,000 mile intervals and they were apparently good all along, if that helps anyone.

 

Ah, the never ending oil debate, every vehicle board has this ongoing discussion with no one agreeing. Just like which is the best tire.

I am with Leeper, I follow the interval as prescribed and have never had any issue with any car I own. I tend to keep cars for 8 years or more for my previous Porsche and BMW, both of which I religiously stuck to the 2 year/15k mile interval. You can find data that supports more frequent oil changes and data that supports the manufacturers interval.

What I do not fall for is the "this is a $100,000 car" and therefore you should just change it more often for that reason. To me it is just a car. But this is a common argument when all else fails.

Matter of fact, my Jag is a $44k car to be exact. And for some that have an older car, it is a $20k vehicle.

 

Yes but how many of us have any long term experience with Direct Injected engines.
Apparently even the manufacturers dont and are only just learning.

If you can pump your gas, you can change your oil. In a Jaguar 5.0 it could not be easier and you wont get a drop of oil on your hands.

Change it every 6 months. If you are wrong you would have wasted exactly $80 dollars a year. If you are right you will gain thousand of miles before $4k repair. The risk-reward is a no-brainier.

Keep in mind absolutely no one saw the problems with DI coming. They all agree clean oil is the best defense. Note: the relationship with direct injection and clean oil was only discovered recently, long after the manufacturer's manuals were printed.

Worse yet. No engineer thought you are going to drive a car so little. Short trips and not very frequent. A killer combination for oil and DI. Also discussed here.
Ask An Engineer: GDI Problems In A Nutshell - The Truth About Cars

 

Not to mention frequent/continuous pulling of a trailer, off roading in the desert or stop/start driving similar to taxi service.

Can't remember seeing too many Jags of any type fitting into that category, never mind an XK.

There's no evidence that suggests the Jag recommended intervals are in any way 'adventurous' and needed to shortened. Beware those who arbitrarily cut them in half with a warning that bad things will happen to those that don't follow suit.

If anything, some of the intervals are starting to fall behind those of other manufacturers who are keeping up with modern materials and methods.

 

Like a politician I have evolved. In the early days it was oil change at 3K miles then as oils improved I went to 5K miles. Then it was minimal of once a year with Syn. oil and now I'm at that stage with the Jag. My Lexus and Volvo are still at 5K but I use dino oil in those . So with the Jag I will now follow the mfg. recommendations and stay with that. As for my pick up truck I just use the oil change message for time to change.

 

to take any guesswork or assumptions out of this equation why not just have a sample analyzed by BlackStone or other testing firm. That is the only way to know for sure whether your oil is within acceptable standards... that way you KNOW and are not relying on a mechanic (who has a vested interest in doing maintenance/oil changes more frequently) or people here who will constantly argue without really having anything scientific to stand on? All of us here on the forum attest to doing what we do because we have always done it "that way" but we don't know truthfully if we are helping or wasting when it comes to frequency that is the bottom line... we can use our own anecdotal experiences but that doesn't mean much of anything in truth.

 

I have done my own oil changes for the last 25 years. Have learned a lot in doing so.
On my truck (which has used Mobil1 or better since mile one, now on mile 250,000 all original parts!) there is a built in reminder, there will be valve-train noise at startup when the oil is above 7months old. Even when the levels are perfect.

I have left the oil in the Jag for a year and it was filthy, way more than my comfort level. Sure some lab coat wearing greenie could tell me that the oil is good for another 3 years. He is welcome to buy it from me then. I will put clean fresh, engine cleaning oil after 6 months. Maybe 9 months if I drove it on the highway everyday. Mine hardly ever sees the hwy.

 

in 1989 bought my Acura new, a few years back gave it to my buddy with just shy of 300K miles ran perfect still got over 30mpg... all that time used the cheapest Castrol dino oil changed every 3K per recommended intervals, all my cars have always subscribed to recommended intervals and have NEVER had anything oil related happened. My current DD (170K miles) gets it's oil changed every 7500 miles per Honda recommendation. anecdotal experiences mean almost nothing on either side of an argument/discussion.

Back to ""lab coat wearing greenie", what they will show is not the color of the oil, which actually means zero in terms of anything relevant (lubricity levels, additives if they are still there and within spec, contamination from coolant or exhaust entering from worn rings, metals due to breakdown, etc) but rather is it still within acceptable levels... seems to be good enough for the military to use on jet engines, aviation in general, etc that has a whole lot riding on it than we do! Color versus scientific analysis detailing every aspect of concern is hardly comparable argument but again you're going to do what you're going to do regardless just as I will. You're going on faith, a belief in the absence of proof, as there's not a shred of evidence that has shown replacing oil prior to mfg recommended intervals has ever benefited an engine in any way. Like God or religion some people will believe what they believe while others will think it's silly and neither side will convince the other of their merits

 

Dont forget the lab coats greenies told us Ethanol was a good idea and safe for engines.

When I say oil gets dirty, I dont mean the color. It becomes sludgy.

 

I was not initially replying to your post. Just making a statement that I have not been able to push syn in my truck past 7 months.

Regarding this post, Oil analysis are fantastic and can tell you all sorts of things. One thing they will not is now much sludge you have building up in the engine. As a result of extended oil changes. And not all oils clean the same. I love Pennzoil ultra for its cleaning ability. And amsoil for the same.

 

Ethanol was not pushed by "LCG's" that was a product of the corn lobby group (actually they are HUGE!) and your friendly neighborhood dirty politician, the same group that said Flint MI water is safe. LCG's knew ethanol was bad, actually so did the corn groups and politicians. That is why they came up with different seals and such to try to accommodate ethanol based fuels and why aviation didn't allow it from the get-go. If you want a feeling of comfort do what they do in aviation as they've got MUCH more riding on things, and they utilize and trust sampling of oils for various reasons especially to show premature wear or possibly preventing catastrophic breakdowns due to things like bearings going or metal shavings in their oils - again scientific analysis versus your ouija-board belief of changing oil every third week or 200 miles whichever comes first :-)

Yeah color and sludge are two different things. On my Jag my oil is as fresh looking at 7K as it is going in

 

The lab coat greeniesare still trying to find proof that it isn't safe for engines as claimed by the tinfoil beanie brigade. It's been 30+ years but they're still at it.

If you've got sludge in your engine despite 6 or 9 month oil change intervals, don't blame the oil or the interval. If shipping costs didn't make it impractical, I'd take your old oil off your hands