I read Greg Bernierś test results from 2006, where he was convinced that 75-90 Hypoid oil was the best. Is that what others agree with?
Does the Moss box share oil with the OD, as does the later, full synchro box?
Probably…?!
There is a Service Bulletin from Jaguar Cars North American Corp., not numbered, but issued on 16 May 1957, addressed to service managers. This is of course applicable only to the non-synchro first boxes, as it would be 8 years before the full synchro box was used.
GEARBOX LUBRICANT
“It is drawn to attention that the correct grade of lubricant for all Jaguar manual gearboxes and overdrive units is SAE 30 engine oil.”
“A number of oil companies have incorrectly indicated that other grades of oil are suitable for these components and it is pointed out that these instructions are misleading and that an incorrect lubricant can bring about mechanical difficulties or failure.”
“Please ensure that only SAE 30 engine oil is used for the manual gearboxes and overdrive units as authorized in factory literature.”
It is correct that the Moss box shares its SAE 30 oil with the OD unit.
SAE 10W-30 is also correct, as the 10W is the Winter viscosity rating and the 30 is the summer viscosity rating. Do not confuse the two numbers, as they are based on two totally different rating scales. I have not heard of anybody trying SAE 5W-30 but perhaps it is because nobody drives their old Jag in subzero F (-18C) weather.
Some people think it it important to use non-detergent oil, in which case you can look for SAE 30 non-detergent oil as used in air compressors.
This instruction does NOT apply to full synchro boxes, which use SAE 90 gear lube, which is based on yet another viscosity rating scale.
My recollection is SAE 30 engine oil has similar viscosity to SAE 75/90 gear oil at 100 degrees C, 212 degrees F. The numerical categories for SAE engine oil and gear oil do not use the same numbers for the same viscosities.
IIRC, the Manual states that the G/B oil should be non-detergent, 30wt motor oil.
Page A24 of the Service Manual gives five brands and types of oil for the gearbox, repeated on page F5 and in the XK150 supplement page 19, which are the same as the summer engine oil, SAE 30. It says nothing about detergent or non-detergent.
I’ve been using EP90 for years! Am I so badly wrong-Got me worried now?
It has to be engine oil. It’s due to the fact that the oil pump in the OD does not work well with the gearbox oils…
Tadek
So I should use 20-50 mineral oil…!!!
AMSOIL has a website page showing some similarities and differences between engine and gear oils at
Redline Synthetic works well, too: IIRC, it is MT-90.
(Its not the same weight as 90w)
CORRECTION: it was MTL I used in Tweety’s Moss ‘box.
EP as in Extreme Pressure? Many EP lubes contain sulfur, and any oil with sulfur in it (especially “active” sulfur)can/will be harmful to “yellow” metals. As I recall when rebuilding my G/B and O/D unit, there were bronze and/or brass parts in there and the reverse gear may have been bronze, too. Personally, I would not use any oil in the G/B unless I knew it was safe for yellow metals. And if you have O/D, there is a mention in the Manual that certain EP lubricants may cause trouble due to the planet gears acting as a centrifuge…essentially separating the oil’s components from one another.
There is some interesting reading out there on the net about non vs detergent 30wt in the Moss box…mostly about aeration and contaminants-suspended-in-the-oil issues…worth some research, IMO.
To follow up…there are at least 3 bronze thrust washers in the O/D unit, and the reverse gear of the G/B rides on a bronze bush…I don’t remember if there any yellow metal thrust washers in the G/B itself since it’s been a long time since I’ve had mine apart. Hope this helps.
I believe the reason Jaguar wanted its service managers to use SAE 30 in their customers cars was all about the synchronizers having sufficient friction. The concern in 1957 was that oil companies were ignorantly saying you could use SAE 90. USA service people, not knowing about this friction requirement, and being in the habit of using SAE 90 in US make transmissions, were erroneously using it in Jaguars. Then the synchros would not work as effectively.
There may have been concern about SAE 90 in the Laycock DeNormanville overdrive, but it was not specifically mentioned in the Service Bulletin.
Unfortunately if we asked Jaguar about it, all their engineers who ever saw a Moss box are long gone, so after all this time we are not likely to get anything from them.
I read the Amsoil and Redline technical bulletins, and one graph on the Redline bulletin shows that SAE 30 motor oil has the highest coefficient of friction at higher RPM. Higher even than Redline.
SAE 90 gear lube EP90 is good for constantly meshed gears and non-synchromesh sliding shift gears. But it has a much higher viscosity at 32F 0C and 0F -18C than SAE 10W30, making it more difficult to squeeze the oil out of the synchro as it comes together, thus resulting in slower synchronization.
Mineral motor oil loses some of its shear stability after high mileage, and as a result you may notice the gears will make more noise in hot weather.
The Redline MT line and Amsoil MTF are synthetics that offer to take the place of mineral oils. Both say they are ok with brass parts.
I tried entering vehicle=XK120 to see what they would recommend.
Amsoil didn’t go back past 1980. Redline recommended MT90.
Redline MT90 approximates SAE 40, so I do not know why Redline recommends it for XK120. Maybe their information is faulty. One can’t always trust internet sources.
Amsoil MTF approximates SAE 5W-30.
So…if I wanted to change from motor oil, I would try Redline MTL or Amsoil MTF as they approximate SAE 30.
Thanks Rob, and all others for your extensive input. I hope that it will be of interest to all other owners of XKs with ODs.
The situation today is slightly different in that all our cars do very little mileage, compared to when they were used daily back in the day. So the wear is far less, and perhaps the oil used is of less importance.
But some oils make gear changing harder, which is not nice and is not related to mileage. I hear different suggestions from not only this forum but from so called specialists in England.
I have Redline MTL in the Moss boxes with no OD attached, and most people agree that this is the best product.
But I have also heard that the OD doesn´t like it, and hence the engine oil suggestion for such equipped cars.
What is the conclusion from the above discussion when it comes to oil for Moss with OD…?
On another note, I have a 150 with the all synchro box with OD, and here I have harder gear changing than normal, esp when the oil has warmed up…I think there is another issue than the oil used in this particular case, but I don´t know what?
Peder
Peder
What oil are you using in your 5 speed, Tremec T5 state automatic fluid, which is what I have and its really a lovely smooth gear change
Morris.
A lit of modern manuals—Volvo comes to mind—use ATF. I used it in my race cars…never had an issue.
I checked my XK150 manual(The black one) and the recommended lubricant for gearbox with OD is indeed SAE 30. My Haynes manual for MK2 Jaguar states EP 90. Early Mk2’s did also have a Moss box. I did a little research and the JEC forum says it something to do with XK’s having the early OD vertical solenoid and something to do with pump.
Anyway I purchased 5L of straight 30 mineral oil (not too easy to find-Comma Classic) and drained both the gearbox and OD. Used opportunity to clean OD filter and there were some small brass particles in the bottom of the big brass drain plug. To be frank the car is hardly used so it probably be good for short journeys. Who knows when I’ll next change it if ever me!!
Extract from:
SERVICE INSTRUCTION MANUAL for the LAYCOCK- DE- NORMANVILLE OVERDRIVE UNIT WITH ELECTRICAL CONTROL
PUBLICATION PART No. 502174.
(…)
CARE AND LUBRICATION
The oil in the overdrive is common with that in the gearbox. The oil to use is ordinary mineral oil in the following grades :–
Normal summer climates - S.A.E.30
Normal winter climates - S.A.E.20
Under no circumstances should extreme pressure gear oils be used, because the centrifugal effect of the planets may separate some of the additives from the oil and cause sludging.