In my more that 1 year struggle to find the engine oil leak on my 2.5L 2004 X-Type I had now the epiphany to mix dye into the engine oil - a dye, which can be detected with UV light. Such a dye is commonly used in A'C systems. When I had that idea I had spend several hours looking at the product description of various sellers of this product:

This dye is normally used for A/C systems, however, I found several sellers, who put in their product description that is can also be mixed into engine oil.
Today this dye finally arrived in the mail. Now I can clearly read, what is written on that bottle - last line: "Do not mix with other oil"
So what shall I believe now?
Does anyone have professional knowledge, if I can mix above product into the engine oil without causing any damage? I would poor the lot (60ml) into the engine oil...

 

https://www.popularmechanics.com/car.../a106/1272471/

 

Thanks, Dell, yes, that is the general idea of how to use the dye - good advise though in your first link, where they recommend to put the dye into some to-be-added-oil first, so that the main part of the dye does not remain stuck near the filler to start with.

I also note that your last link shows exactly my product (A/C dye), and the text there describes it as "Universal UV dye", which means that it could be added to the engine oil. I also found this "promise" on some sales-ads, but in contrast to that the bottle itself says "Do not mix with other oil".

Hence my confusion, and I am hoping that we have a professional mechanic out there, who knows for sure, if that product, which I have does the trick without doing damage to the engine...

 

Hallo Peter,
wir nehmen diese Farbe nur für Wasserbasierte Flüssigkeiten. Entspricht LIQUI MOLY Fluoreszierender Lecksucher K. Für Öl nehmen wir LIQUI MOLY Fluoreszierender Lecksucher für Hydraulikanlagen. Es wird den Motor nicht beschädigen könnte aber zu einere Emulsionsbildung führen. Ölwechsel ist dann unerlässlich.
Hello Peter,
we only use this color for water-based liquids. Corresponds to LIQUI MOLY Fluorescent Leak Detector K. For oil we use LIQUI MOLY Fluorescent Leak Detector for Hydraulic Systems. To the luiqid you bay, it will not damage the engine but could lead to emulsion formation. An oil change is then essential.

 

OK, danke. Also falls ich es nicht schaffe, ein 100% geeignetes UV-dye zu finden, dann koennte ich also das vorhandene verwenden und dann eben einen Oelwechsel machen. Danke.
(OK, so if I cannot find a more suitable UV-dye, I will use the one I have followed by an oil change. Thanks.)

Deine Liste von Fahrzeugen enthaelt einen XJ330 6L V12 von 1997!? Was ist das denn? Hab ich noch nie von gehoert... Google kennt es auch nicht.
(What's a XJ330 6L V12 from 1997?)

PS: I checked and found that I cannot get hold of that Liqui Moli stuff here in Australia. But I found instead Auto Pro dye (for more than 3 times the price of the other product above):

Is that any good (i.e. can this be mixed into the engine oil without causing damage to the engine and without requiring an engine oil change directly after use?) ?

 

Hi Peter, thanks for the reply. I made a mistake with the XJ. I have changed it.

 

Oh wow, nice car - I did not know that Jaguar (indirectly) still produced a V12 in 1997...:
So your Jag is a XJ12 aka X330:
The X330 is the long-wheel base version of the X300.
And while Jaguar produced the last XJ12 in 1995, Daimler produced the last XJ12 in 1997...

PS: Update on my little project: I decided to use the UV-dye, which I have already, look for the leak and then do an engine oil change.
I was pondering, which way to go, but since a local shop currently has a good special going on for 5W-30 full synthetic oil, I made my decision.