Hi, I have a 2004 XJ8 with 31500 miles on it. I had my 30000 mile service done a couple of months ago. What does anyone think about changing to a synthetic oil at this stage, is it worth it or not. I would appreciate your opinions. Thanks Ed.

 

And opinions you will get!

Ah, the great oil debate. I'm sure I am stepping right in "it", but here goes:

I like to use synthetic oil in my Jaguars primarily because it extends the change interval. Synthetics also improve cold startup conditions over mineral oil, but that isn't an issue for me.

On change intervals, synthetics have been shown to hold their additive package longer than mineral oils. I've proven this to myself by taking oil samples a couple of times and had them tested at Blackstone. One sample from my XK8 was taken with 15K miles on the oil and blackstone reported I could have extended the change another approx 5K miles. That was the longest I've gone. I now do about 12K changes with one or two oil filter only changes, either one at 6K or two at 4K miles.

Dino oil works just as well in terms of providing the engine with proper lubrication and cleaning, but the additive package tends to run out sooner, and multi-viscosity blends tend to have a narrower range in extremes, repeat, extreme temps.

BUT, you pay less for mineral oil than synthetic oil, so pretty much, the cost per mile is about the same. Just how frequently you want to be on your back getting an oil shower or at the Jiffy Lube is more the difference between mineral oil and synthetic.

OK, thats my "opinion" I am opening up my umbrella now!...and making some popcorn!

 

Castrol Syntec in both of my Jags.

 

Mobil one in my 04 and Stop Tech full synthetic in my 96

 

Unless you're going to make full use of the extended change interval, there's no real world advantage to synthetics.

 

Well put Mikey, I completely agree. I can't believe it when someone says they use synthetic oil and change it every 3K miles. It's as irrational as putting new tires on the car every 3K miles.

 

Thank you gentlemen, your opinions are much appreciated. I was not thinking too much about the oil change intervals, I was wondering if it in fact it extended the life of the engine over regular mineral oils.

 

I read an article years ago in a hot rod magazine about an independent test conducted, to compare synthetic and regular motor oils. They chose two populations of NYC taxi cabs, which is considered fairly severe driving conditions. The population with regular motor oil had their oil changed every 3k miles up to 60k miles. The population with synthetic oil NEVER changed the oil up to 60k miles. They only added oil as necessary and changed the filters at certain intervals. At the end of the test, they broke down all of the engines. The regular oil population showed significantly more gum and deposits throughout the engine than in the synthetic population that never changed the oil. I recall a picture of the oil screens, and the synthetic screens were very clean and the regular oil screens had buildup. I've been running Amsoil and Mobil 1 ever since, and I change it once per year in all cars, which is somewhere between 8k and 12k miles. I strongly believe that there is no comparision between regular and synthetic oil. Also, synthetic oil is man made, and reduces our reliance on the Arab nations, which I think we would all agree is a good thing.

 

I use MOBIL 1 full synthetic with a k&n oil filter and i change it every 5000 miles.

 

There is no evidence to support this. A poster above quoted part of a study using NYC taxi cabs. It is true that the engines run on synthetics were 'cleaner', but showed equal wear to their dino fed brethren.

 

Actually Mikey, I have a hard copy of the article here at my desk. It was an article titled "Synthetic Oil Secrets: Fact or Friction", and it was published in Camaro Corral Magazine. The actual quote was, "The Amsoil group of cabs had substantially less sludge and wear compared to the cabs using petrolium oil". The article also goes into great detail about the extraordinary durability of synthetic oil compare to petrolium, and said that most synthetic oils perform better after 10,000 miles than newly installed petrolium oil. Jet engines use synthetics, the Space Shuttle uses synthetics, Vette's, Vipers and AMG's are all delivered with synthetics, because it is a superior product.

 

Well I for one have never used synthetic, and have never had any problems, but I do change oil and filter more frequently perhaps than the manufacturer recommends. Surely frequent oil changes are better than just running on the same oil for 10s of thousands of miles ? As miles build up the water and acids that are passed from the combustion chambers via the piston rings into the engine relentlessly accumulate in the oil. Frequent oil changes mean these do not build to serious engine-damaging percentages. So synthetic or not, frequent changes are better, in which case why pay so much extra for the synthetic ?

I rest my case !

 

Fraser,

Have you ever considered taking an oil sample for analysis? If not, you'd probably find the results very interesting. It is pretty amazing the comprehensiveness of a lab study like one that blackstone produces. It takes all the guesswork out of the "right" change intervals and will tell you exactly what's in the oil. From that, the report will even deduce the condition of some engine components, etc. From trace elements in the oil, they can early detect bearing wear, etc. If there is water buildup in the oil, they'll see it. They also estimate any life left in the oil, or if you've overextended the interval.

Up to about 7 years ago, I was "old school", applying lots of traditional theories about oil change intervals, oil types, even oil viscosities. After the first sample I had done, it completely changed my theories. The analysis is only about $20. I've only done a couple of these. That's all it takes to help establish a new pattern based on your driving habits, location, car, climate.

So there are no misconceptions, I have no business interests in Blackstone labs more than as a customer.

 

Yes, I'm aware of that article- sponsored and published by an obviously biased oil manufacturer. I was referring to an UNbiased source, the original taxi cab test:

http://www.moneybluebook.com/article....oilchange.php

Here is a similar report from Amsoil themselves in which they report actual wear figures.

http://www.worldsbestoil.ca/taxi-test.php

The point could be argued that the wear 'was half of dino oil'

Control Group: Petroleum
3,000 Mi. Oil/Filter Change Group B: AMSOIL Synthetic
6,000 Mi. Oil/Filter Change Group C: AMSOIL Synthetic
12,000 Mi. Oil/Filter Change Group D: AMSOIL Synthetic
Fill for Life *10 = clean
but the wear on any of the engines at that level of mileage is neglible, so the OPs point 'do the engines last longer', the answer is still no.

As to the use of synthetics in aircraft engines, I have recently retired from a 31 year career at worlds largest manufacturer of gas turbines and can assure you that synthetics are NOT used in these engines because of supposed superior lubrication properties. Apples and oranges.

 

To your question, it is impossible to find an example of a failed engine that had any type, brand or weight of modern engine oil in it with the correct amount and changed, along with the filter, at any reasonable interval in the range suggested by the manufacturer.

Oil has three main functions in an engine:

1. Lubrication
2. Cooling
3. Cleaning

Assuming an otherwise healthy engine in all technical terms:

As long as the correct oil level is maintained, oil will keep lubricating forever.

Also, as long as the correct oil level is maintained, simply by fact that oil is a liquid, the cooling will keep occurring.

The real question is - how long will the oil keep cleaning? Or, when does it become saturated with contaminates, and/or lose its additive package (additive package is primarily a cleaning function). This really determines the change interval.

Engine crankcase contaminates come from simply driving the car. There is a minute amount of blowby in any healthy engine that will introduce exhaust gasses in the crankcase, fuel contaminates, even anti-freeze shows up in very minute amounts. The contamination is exacerbated by different driving conditions and climate conditions. Frequent cold starts and very short trips, combined with a high humidity climate produces far more crankcase contaminates than a car that does all highway driving in an arid climate.

It is normal and should be expected that oil comes out a different color (dirty) than when it went in. That means it is doing its job. Good filtration keeps solids from recirculating in the oil on long change intervals and is why I've moved to 12K synthetic changes with interim filter only changes.

Long answer, but expect your engine will completely fail for any reason unrelated to the type of oil used; or, last forever for the same unrelated reasons.

 

The above echoes the results of my own research- oil related failures and/or excessive wear resulting from use of one brand or type over another are a thing of the distant past.

Kinda like the laundry detergent or soft drink market- constant marketing that their own product is better than before and 'proven' better than the competition.

 

A couple misconceptions that I thought I would mention....synthetic oil is made from petroleum just like the standard stuff, it's molecules are just modified in the base stock and the processes and additives are different. In addition, the USA only gets about 10% of its oil from the MidEast, the majority of it comes from.....Canada, then, at much smaller percentages....Mexico and Venezuela.

 

Another very good post, thanks!

Oh, thanks for buying our oil too

 

It's all routine maintenance. The key here is to just do it!! And put what ever you want in your car, thats why it's yours. We all buy what we like....cars, clothes, electronics, oil, etc. I think we all should avoid 4 subjects 1. Religion 2. politics 3. oil and 4. transmission fluid changes

 

A jag tech told me to keep the conventional oil because my 2004 xj8 does not take synthetic but another tech in the same store told me that's nonsense that syntech oil it's better for my kind of driving since I drive about 40,000 per year to the northern states