My fan also started making noises last year but a squirt of Tri-flow after I took it out fixed that right up 
Is triflow an oil?
Glad to hear that. I did not have time to search the thread because I was on my way to the trail. I am curious,where is the link to those?
I thought I got them all on Ebay.
Where is OP at?!! He started the thread and has not been seen since!! 
@Chris DISREGARD THAT link I posted below for the Barrel connectors! The listing ended and the ones they posted are WRONG!!
https://www.ebay.com/itm/7-9-5-5mm-DC-Male-to-5-5-2-1mm-DC-Female-Power-Plug-fo-Lenovo-IBM-Laptop-Adapter-/253600326860?
oid=142340377628
I have Two spares I can send you if you want. send me PM w/ your address
Yes. I use the spray-on can but you can get it in squeeze bottles, etc. To be honest I haven’t notice much difference in light oils and I think there’s a lot of marketing hype regarding them.
These are the ones I got a while back , they were just over £3 but now they’re only £1
With these I can pick the opus up & move it around with no loss of connection.
Look what I found on AliExpress
http://s.aliexpress.com/IFfMVbqa
Apologies …. I got crazy busy at work as soon as I posted and then had friends come to stay over the weekend …. I kept meaning to check it but just haven’t had a chance.
I left it unplugged and have tried again and it seems fine now which is really weird, I got 4 x 18650’s and put them all in at the same time and the fan cut in as it should.
I hadn’t put the battery in the wrong way and did try using magnets on the ends before I posted this thread.
Think I may oil the fan anyway as it’s always been noisy, is there any oil I should use … is 3 in 1 OK or silicon spray any better
I’ll also look at the fan upgrade that’s been mentioned although I just want to make sure the unit’s OK before I spend the money on that and find the issue I had was the start of it breaking down and don’t see what else I can do but keep using it for now and see if the error occurs again.
I used Tri-flow oil on mine last year and it’s been running quiet since then. I think for the most part that any oil/grease would work effectively for this particular purpose.
I use 3 in 1 spray , it’s a little thinner than the caned 3 in1 oil.
Just charged 4 x AA’s with it with no problem … took them out and went to replace with the next 4 and it just said Null on each slot …. definitely not a happy charger it seems 
Further Update …. Switched it off, left it for a while, switched on and put the 4 x’s AA’s back in, all registered a voltage and left them to charge, fan cut in after a short while.
Left it for about 10 mins, went to check and saw the voltage hadn’t changed on any of them, switched through the display and it showed 2 mah had gone into each of the batteries, checked the time and they all said 0.00 … touched one of the batteries …. another 5 mins and I think it’d of been searching for the fire extinguisher and couldn’t hold onto them as I took them out of the charger so probably destroyed 4 brand new batteries as well.
My conclusion of the Opus BT C3100 is it’s a DANGEROUS POS … really hasn’t been a good experience for me at all.