The more threads about the various coolant types I read, the more conflicting the info seems....several threads advocate using G-05 in cars factory-filled with "Jaguar Yellow, Dow D-542" Sadly, Dow D-542 seems to exist only in the mind of Jaguar - my internet searches ad nauseum have been fruitless.

So, I wrote Valvoline (makers of Zerex) and this is their reply:

" Status: Customer Responded Date: 11/25/2011
Time: 10:18:01 Creation Date: 11/23/2011
Creation Time: 21:18:00 Created By: feedback@valvoline.com

Description:
Thank you for your response. Unfortunately Valvoline does not recommend the Zerex G-05 Antifreeze/Coolant for the Jaguar Dow D542 specification. We would recommend the Zerex Dex-Cool Antifreeze/Coolant for the Jaguar Dow D542 specification, whether you choose to use the coolant as a top-off or a complete drain and fill service.
Valvoline recommends the Zerex G-05 Antifreeze/Coolant for Jaguar vehicle models 1995 and all prior years. The Zerex Dex-Cool Antifreeze/Coolant would be recommended for all Jaguar vehicle models from 1996 - present. If you have any further questions, please feel free to contact us via email or by phone at 800 TEAM VAL for assistance. Thank you once again for your question.

Incident Information:

Submitted Via: Email "

SO - this seems straightforward. And authoritative (?). Yet several posters warn about mixing DexCool with Jaguar Yellow. The more I read, the confuseder I get!

 

They have no idea what years the DOW YELLOW was used.
The Yellow is used up to 1999MY Jaguars.
The S-Type (listed as a 2000MY in the US) and all 2000MY jaguars switched to the orange XL coolant.

See the list of TSBs I submitted in a different post.


The DOW D542 is not as different from Zerex G-05 as the orange XL Coolant (OAT)

Just drain the D542 and top up with G-05 and you should be good to go.

G-05 is probably compatible with Dow D985 so here is a TSB for you.

bob gauff

 

It depends on what you want to use, what you already have in there, and what factory fill was.

That will determine how careful you have to be about flushing.

However, the G-05 is a licensed BASF Glysantin formulation as was presumably the Jag Yellow.

If you are changing types, flushing is mandatory, and lots of it. Once you are done flushing ... flush some more.

When you refill afterwards start with full strength and not the premix because you already have water in the system to dilute the antifreeze. Otherwise, you will end up mixing diluted antifreeze with even more water.

 

I need some help clarifying what antifreeze to use in a 1991 XJS, V12.
I think I need to pick between Zerex G-05 or the original Jaguar JLM204043 and need to verify these two coolant specs and applications to the 91 XJS.

What was the original 1991 Jaguar XJS antifreeze. Was it Jaguar # JLM204043? This is what my local Jaguar dealer sold to me for my 91 XJS.
Is JLM204043 the same as D542?
Who made or makes D542?
The original antifreeze was phosphate free per the owners manual. Was the original antifreeze also nitrate free and silicate free?
Zerex G-05 and JLM204043 are both yellow.
Zerex G-05 is phosphate free, but contains nitrates free and lowered silicate.
Does Zerex G-05 meet the BS 6580 standard?
Is Zerex G-05 an acceptable and safe replacement for JLM204043 in the 1991 Jag XJS, V12?

Autozone shows the Pentosin NF antifreeze as fitting the 91 Jag XJS, also show Zerex G-05 and many other products as acceptable. The Pentosin is a bright blue color. I have not confirmed the specs on Pentosin NF. O'Reilly Auto Parts shows a different Pentosin for the 91 XJS.


Thanks

 

Zerex G-05 would be an excellent choice for the XJS V12. I ran mine on it for 4 years. It is always a good idea to flush the system properly when switching coolants.

There's a lot of rot talked about coolant. In general, it is far more important that your coolant is fresh and in good condition that exactly what kind you use. The main compatibility issues are :

1) Old engines with a radiator cap on top of the radiator - no expansion tank or catch tank : Dexcool doesn't like these, as it doesn't like presence of hot oxygen, which is what you get at the top of the radiator.

2) Mixing Dexcool with the old green stuff.

Colour of coolant is a very poor guide to its type. There is little or no consistency across the marketplace. Yellow could be Jaguar, Prestone Universal, or any of a dozen others.

That's why, if you didn't put the coolant in yourself, and don't know what you have, it's best to top off with distilled water, or the Prestone Universal.

 

Thanks very much.

Is it possible to verify that the.original Jaguar antifreeze was JLM204043 in the 1991 XJS and is this also known as D542?

I have to replace a leaking water pump and will flush the cooling system and replace with new coolant. I have been topping off the system with the Jaguar JLM204043 that the dealer sold me last year. The prior owner had maintained the car well with dealer service and I thought I should use the genuine Jaguar antifreeze when I was topping off.

The Zerex G-05 appears to be a good choice for the full replacement after flush.

I would like to verify how the Zerex G-05 Nitrate and Silicate content compare to the Jaguar JLM204043,

 

Rather than using a Jag part number, use the specification required by Jag. It should be listed in the owners manual.

Never ever use colour as a guide. It's irrelevant.

 

Thanks, Mickey.

My manual refers to the BS 6580 spec if something other than Jaguar Antifreeze is used. A search of BS6580 in the these forums shows more information, but leaves unanswered the clear history of what Antifreeze was use in the 1991 XJS and other 91 Jags. I've read through all the posts and references and still cannot confirm what was the original, but the reference TSBs may be saying that Jaguar used a D985 originally and later this was replaced by a D542 antifreeze which is apparently the JLM204043 antifreeze. That referenced TSB called out an 1997 XK8 which required replacing the blue-green D985 with the yellow D542 (jLM204043). I have not found any label in my engine compartment about a coolant change per any Jaguar TSB.

Jaguar sold me the JLM204043 when I asked them for the appropriate antifreeze to top off my 91 XJS.

Now that I need to change a water pump, it looks like I will be draining and flushing. Based on all I have read I think I can use either JLM204043 or Zerex G-05, but I did not see a statement that Zerex G-05 met BS6580. The literature from Valvoline calls out specs for G-05, but does not include BS6580. The jug of JLM does not call out BS6580, but I believe it does based on those TSBs calling out the JLM204043.

As for the Pentosin NF, there are forum comments that this is also Ok for the early 90s Jags, but my reading and interpretation of those comments is that Pentosin NF may be closer to the original antifreeze (I think D985) used in the 91 Jags than to the JLM204043 (D542 recommended as replacement in the TSB). Autozone says Pentosin NF fits the 91 XJS.

The inhibitor chemistry in JLM204043 and in Zerex G-05 is not clearly stated in what I have read. The G-05 is phosphate free, but does contain nitrates (to protect dispel engine cylinder liners from cavitation) and does contain silicates (220-250 ppm).

Can anyone confirm that D985 was the original antifreeze used in the 91 XJS and that this was replaced by JLM204043 (D542)?

Can anyone can confirm the inhibitor chemistries (OAT, HOAT) and that Zerex G-05 is a safe substitution for JLM204043, for the 91 Jag, assuming flushing?

If anyone has a TSB on the 91 Jag coolant, that will also be helpful.

 

You really are over-thinking this. Flush it out, put in a quality coolant. It really doesn't matter which one as long as you flush it out first, and change it when it's due.

I think HOAT coolants are a good choice as they combine the longevity of an OAT with some silicates for backward compatibility.

Zerex G-05 is an excellent HOAT coolant, and there are many, many others. It doesn't matter which one you use.

 

This might help:

all makes - Antifreeze- Blue vs Orange/Red | Technical matters | Back Room Forum | Honest John

"There was one grade of antifreeze / coolant, manufactured to BS6580 (1992) and it was Blue.
Now the majority of modern engines are designed to use a specific grade of antifreeze / coolant and the one thing you can guarantee is that modern vehicles will not have BS6580 as the specified product. BS 6580 is now a minimum quality standard for antifreeze / coolant that has been largely replaced by vehicle specific grades such as:

Audi TL774-D, Ford WSS-M97B44-D, ISUZU, Renault D, Jaguar WSS-M97B44-D, MB 325.3, SAAB 6901 599, Seat TL774-D, Skoda 61-0-0257, Vauxhall QL 130100 and Volkswagen TL774-D."



Jaguar WSS-M97B44-D supercedes BS6580 it seems.