Originally Posted By: Ramblejam
Kam,
Stop.
You're going out and trying to find an oil without any actual knowledge of what you're looking at.
75/80w-140 API GL-5/MT-1 oils are available anywhere.
Interesting thread on the engine oil. I found a similar low miles XPAG engine that had sat for over 30 years with (fortunately) clean oil in it. The guy (old friend of the family sort of thing) said it would start right up once I got the ignition renewed and rebuilt the carbs and fuel pump, etc.. I knew the oil pan (sump) was a sludge collector in these engines so I removed the sump cover (pan) and slogged out all the sludge and cleaned up the pickup screen, checked things over, etc. I used some modern 5W30 when ready to start for first time, and it did start right up. Car was not ready to drive yet so I would leave it to "idle" at about 800-1000 RPM to get good and heated up. Did that several times then changed to 10W40 and repeated. I rejected all people who said I should run kerosene or diesel (yeah right) mixed in the oil to "clean it up inside." I changed out the light weight oils a few times when it showed any signs of getting dirty, which it did for a while. By the time it was ready to drive I went with a heavier multi grade like the Rotella or Delo. Oil now gets dirty at a "normal" rate.
My uncle raced an MG Special for years from the 50's thru 70's. It was MG TD chassis based, with the rack and pinion steering and front independent suspension. So it had the XPAG or XPEG (1250 & 1500 cc)and he insisted on using the TC transmission. I don't recall what he used for the differential. He said the TC transmission was heads and shoulders better than the TD and TF transmission, which he referred to as totally unsuitable for racing. What I am getting at here is that the TC and maybe the TB tranny is somehow quite different from other MG's of the era. I seem to recall MGA based racers sometimes also preferred only the TC tranny. The TC & TB manual calls for 140W in the tranny, and no other MG except for the quite rare 18/80 used 140W. I found a Pentrite advert chart that shows this about the TC tranny and all the other MG's here:
http://www.geomatique-liege.be/MGJP/DocumentsPDF/PenriteMG.pdf
I don't know if the above quote refers to differential or transmission, but is not the point being made that a modern gear oil with GL5 and MT-1 ratings mean that is safe for yellow metals? Both the Tranny and Rear end (I am pretty sure) on TC have brass caged bearings and maybe bronze in the synchro's which might benefit from such a yellow metal friendly oil? The tranny on the TC for some reason MG calls for 140W on this one only. I wonder what it could be about this transmission that is so robust and high competition potential (which is pretty much the opposite of how Kam describes it) that it (MG) specifies 140W? Seems like GL4 140W is still readily available. I would stick with 140W in the tranny until you have a better idea why MG (uncharacteristically) called for 140W.
And would not the above quote idea on multi weight MT-1 GL4-5 work well in the differential, assuming there is still some brass caged bearings in there? Remember this is not even a hypoid technically, so 140W is not so strange, I don't think. I could see how something like a copper friendly 85w140 multi weight gear oil could be an upgrade, though. I am not saying for the tranny but for the diff. Not sure what sort of modern multi might be best in the TC tranny.
