Engine Oil

[DevilDog]

I know we discussed this before but the sites search engine comes up empty. What type of engine oil do all of you use? The book recommends 20W 40. Is this correct?
Thanks

[NigelW]

I use Castrol XL 20w50. I noticed that the new Jaguar XKSS costing a million pounds that was built at Ryton on the TV program the other night was filled with this oil. Glyn said to use a synthetic or semi synthetic oil so have been contemplating switching to it on the next oil change.

[Glyn Ruck]

Joe. Jaguar was happy with SAE 20W, 30 & 40 Monogrades in XK engines in different ambient conditions & even SAE 10W-40 in the Multigrade era. (20W-50 is on the heavy side by modern thinking unless you have a worn engine with a rebuild inevitable)

There is absolutely nothing wrong with using the very latest modern Synthetic oils of suitable viscosity in an XK engine. I advise using mineral oil of max SF level to run-in/bed-in/break-in a newly rebuilt engine (first 1000 miles) or it will take forever with modern oils. Run-in should avoid long periods at constant throttle & very high RPM. Varying throttle draws oil into the ring belt on overun which is desirable. After first 500 miles bursts at WOT are recommended. Watch the temperature gauge & back off if temperature climbs unduly.

Modern synthetic engine oils will substantially increase the life of an XK engine & due to the vastly better HTHS (High Temperature High Shear) performance they offer your cam & tappet area will be far better protected. XK engines due to long stroke have pretty high piston speeds & modern additive/base oil technology will reduce wear here by a large margin.

I am running in my engine on SAE 40 SF quality level mineral oil.

Thereater I will use a full synthetic SAE 10W-30 or 10W-40 approved against Mercedes spec 229.5.

Avoid so called "Classic Oils"

[Orlando St.R]

My engine had done 7,000 miles since rebuild. I have been using mineral 20W-50s - Castrol, Millers, Penrite, etc.

Last year I used Penrite 20W-50 Classic Mineral (https://www.classic-oils.net/Penrite-Classic-20W-50), which I chose because it uses Group 2 base stock (and therefore I thought it would be better). After about 500 miles, I noticed the oil pressure falling off as the engine got really hot, to the extent that at 3,000 rpm, it was barely touching 40psi. I'd bought the Penrite from Classic Oils of Bicester (https://www.classic-oils.net). I mentioned to owner Guy Lachlan what had happened and he offered to have the oil tested. So, I drained the Penrite and replaced it with Guy's own brand (https://www.classic-oils.net/Classic-Oi ... tage-20W50), which performed fine for the rest of the year. Anyway, the test came back to say that the Penrite had 'fallen out of grade' (ie. no longer met the advertised viscosity at high temperature), probably from getting too hot.

So, this year, I have swapped to Penrite HPR15 (https://www.classic-oils.net/Penrite-HPR15), which is a synthetic 15W-60, but with an additive package designed for older engines. So far, so good. Oil pressure is great, as you would expect!

The moral of this tale is that:

• (a) it pays to keep your eye on the oil pressure gauge,

• (b) our engines do get very hot - Nigel has even fitted an oil cooler

• (c) I absolutely concur with Glyn about the better high temperature performance and longevity of synthetics.

PS:

I use Castrol XL 20w50. I noticed that the new Jaguar XKSS costing a million pounds that was built at Ryton on the TV program the other night was filled with this oil.

As Castrol is the only brand of oil recommended for moderns Jaguars, I think it was almost inevitable they would use an oil branded as such.

[Glyn Ruck]

I'm a Tribologist by training.

So called "classic oils", blended by these boutique blenders & some of the main stream are ultra cheap to formulate 20W-50's & 20W-60's using ancient cheap additive technology at low treat, bags of VI Improver (Viscosity Modifier in US speak) that is cheap milled polymer & cheap Group 1 mineral Base Oils. Group 2 is better but cannot match full synthetics. It's just a BS marketing ploy. Some manufacturers even have the cheek to charge a premium for them. They should sell for a cheap & cheerful Halfords house brand price.

The old school VI Improvers used in these ancient & obsolete formulations are not shear stable & shear out of grade. What starts as a 20W-50 will frequently end up shearing to a 20W-30. The strands of polymer literally get chopped up into little pieces & no longer fulfill their function.

Synthetics ~ apart from their superior HTHS performance thin considerably less than their mineral counterparts for a given change (increase) in temperature. So called high Viscosity Index base oils. The Viscosity Index of an oil is the rate of change in viscosity for a given change in temperature. The higher the VI the less the change.

When using high VI synthetic base stocks one has to use far less or no VI Improver to achieve a multigrade oil so they stay in grade/maintain their viscosity over their full service life. Also modern VI Improvers are vastly more shear stable than the rubbish put into so called "classic oils".

There is really no such thing as an additive package that is suitable for older engines. They benefit from the best they can get. The best goes into premium synthetics.

Jaguar engineers from the 50's & 60's would have loved to have the modern lubricant technology available today. They recommended the best available at the time.

The reason you will see me recommend products of suitable viscosity approved against Mercedes Benz 229.5 spec is that products that get through the rigorous Benz testing regime will exceed the requirements of all production gasoline engine manufacturers. VAG Group, Porsche etc. etc. AMG's performance engines are far more difficult to lubricate that our Jaguar XK units. An example is the A45 M133 engine which is one of the highest power density production engines on the market.

BTW ~ our additive company supplies all the additive packages used in Castrol engine oils. All the major oil companies make fine products as long as you buy their premium ranges. Boutique companies simply do not have the research budgets, facilities or technology. They buy in what they use.

[cass3958]

Thank you Glyn very informative.

Question though about engine oil service. Driven normally ie not driven quickly at high revs to create a hotter than normal working temperature, what would you say is the normal life of an oil in miles?

Modern engine manufacturers seem to recommend an annual oil change at service regardless of the miles driven. They also have service mileage points and recommend the oil to be changed after say 12,000 miles. An average yearly mileage on a modern car is in the UK about 12,000 miles but in our S Types it might take us 5 years or more to run 12,000 miles. So what is the life of a decent oil? Should it be changed on the number of miles driven or is there a shelf life for an oil just sat in the bottom of an engine doing 1500 miles a year?

I bought my car with 70975 miles on the clock in June 2013 and then rebuilt the engine completely. The car was put back on the road in November 2014 and I now have 76909 so have only covered 1200 miles a year.

I have the periodic service voucher booklet for my car. The first eight vouchers have been used but the 9th is for 24,000 miles. It recommends on the back of the voucher an oil change. So does the next one at 27,000 miles and the next at 30,000. It recommends an oil change every 3000 miles right up to the last voucher at 60,000 miles.

Do modern oils last longer?

Was this an overkill by Jaguar or were engine oils in the 1960s of such poor quality compared with modern oils that this was a necessity rather than a way of charging the owners for a service that was not really required.

Do we owe the long life of our engines in some cases to the regular oil servicing that was used?

[Glyn Ruck]

The operating life of an engine oil is usually determined by it's level of contamination by the likes of combustion by-products, silica (dust), wear debris, water, oxidation by-products, fuel etc. Standards of both oil & air filtration have a large bearing on this.

With top filtration a good rule of thumb for premium synthetic engine oils is about 15000Km/9000 mile drain intervals. Extending beyond this should only be done with an oil sample analysis regime. Additive depletion is not an issue unless drain interval is substantially increased.

The reason that annual replacement of engine oil is recommended by OEM's is the alarming rate at which water builds up in the sump of vehicles on a normal duty cycle. Water is a by-product of combustion. I have personally done endless dyno testing of fuel consumption with friction modified engine oils over 10 & 20Km from a cold start. It does not take long for water content in the oil to rise to 7 & even 10% in these operating conditions. It takes a very long time at full operating temperature to drive this water off. Far longer than many might expect so water levels steadily rise. Water is a poor lubricant & even with corrosion inhibitors in the oil some internal corrosion can occur in engines.

Drain intervals have increased from those recommended in the day by Jaguar due to advances in lubricant technology, filtration & fuel. e.g. fuel sulphur levels have steadily decreased.

Oil is cheap when compared with the cost of an engine rebuild. I recommend that people err on the safe side with oil drain intervals.

[DevilDog]

Thanks everyone for their comments.....great info.

To summarize: Full synthetic SAE 5W-40 approved against Mercedes spec 229.5. This looks like a great choice.

oil.jpg (99.08 KiB) Viewed 2422 times

[Glyn Ruck]

You are on the right track but NO. This product is not approved by Benz. Who is Triax Lubricants? Some boutique blender that has not achieved an approval. Stick to reputable oil company products.

Avoid products that use weasel wording in/on their labels. Most prevalent in the US. Avoid claims like ~ "For" or "Is suitable for" or "Meets the requirements of".

Only use products that state "Approved against Mercedes Benz 229.5" ~ "Holds Mercedes Benz Approval 229.5" etc.

Mercedes make this easy for you by listing all approved products.

Here is the latest global listing as of 6 May 2019.

https://bevo.mercedes-benz.com/bevolisten/229.5_en.html

Remember only use these premium products after run in/break in or you could severely retard the process.

[NigelW]

Something else you might like to shed some light on Glyn is the shelf life of oil, I've read a lot of contradictions on the subject. - thanks.