Hydraulic fluid for total loss lubrication

[Brad_C]

G'day all,

I do a lot of small motor repair and I run some old British machinery with Oilite bushes and white metal bearings. The recommended lubricants for these are Hydraulic fluids with ISO between 32 & 100 depending on the bearing.

The motor bearings are generally recommended to use Royal Purple Synfilm 68. The only problem I have is in Australia it is only available in 5Gal qty and only in multiples of more than one container (thus making it effectively unobtanium and certainly unaffordable).

The predominant quality required of all of these fluids is long term oxidation stability. They are all open bearings and really need a fluid that will be stable long-term. None of these machines are particularly high load or run at high temperatures.

The only synthetic lubricants I appear to have access to are Amsoil Compressor oil, and then only in 46 & 100 grades. Being designed for compressors I'd have thought it'd need to be extremely resistant to oxidation. Could I mix the 46 & 100 to come out with something like a 68? Would Amsoil Compressor oil in this use case come anywhere near the RP Synfilm for longevity?

My lathe specs ISO 32, but i figure 46 might be close enough for the light use it sees.

Us Aussies are pretty jealous of the range and pricing you guys get.

 

[MolaKule]

Quote:
Could I mix the 46 & 100 to come out with something like a 68?


Yes, mixing the two will get you an ISO 68 oil.

Quote:
Would Amsoil Compressor oil in this use case come anywhere near the RP Synfilm for longevity?


Probably better.

 

[andyd]

Are Oilite bushings made of powdered bronze with pores in it to absorb oil? The bushings on my old BMWs' heater motors would be dry after 15 yrs. I have rejuvenated a few by soaking the ends of the motor in ATF for a day an end in hopes of re-oiling the bushings. Just curious, is what I'm doing of any use?

 

[MolaKule]

I would soak them in a AW hydraulic oil of about ISO 68.

The oilite bearings should have a wick touching the shaft or bearing.

Oils do volatize over time and with heat.

 

[Brad_C]

Ok, so 5 Gallons of Amsoil ISO 68 hydraulic oil is $420 and it'd take me about 300 years to use it, so I've pulled the trigger on 2 qts of 100 and 2 qts of 46 compressor oil. I'll just mix them up in the numerical ratio required to make 68 and see how it goes.

MolaKule, you are spot on. The recommended oil for most light use oilite bushes is an anti-wear hydraulic oil of ISO 68 (which is why I was looking for some).

The best way to re-lube them is to take the bushes out and cook them in something like paint thinner to dissolve any leftover grunge, then dry them as best you can and boil (well, more like simmer) them in the oil. You can also just submerge them in oil for a couple of days but I can justify the lab hotplate and beakers to the wife if I cook the oil into them.

andyd, if your BMW heater fan is anything like my Volvo units the bearings will be surrounded by a circular felt wick. Your soak in ATF is the right idea, just with a less than optimum fluid. I dismantle mine and treat them as above (although I've sacrificed a unit here that I'm currently putting ball races in).

For reference at all the cheap auto stores here you can buy air compressor oil and air tool oil. The compressor oil is ISO68 hydraulic oil and the tool oil is ISO32.

 

[Datsyuk]

What is the oxidation hours requirement?
You would have to double check on some technical sites, but as I remember its possible to use 10w40 motor oil instead of hydraulic. If so, wouldn't synthetic 10w40 be a solution?