Hydraulic oil

[MattF]

Exempting the obvious main use of hydraulic oils, what other purposes are they suitable for. Are they actually a good lubricant, similar to a single grade oil, which could be used in compressors and for older machinery's bronze bearing for lubrication, for example? Also, if it's specified as a 32, 46 or whatever, is that just referring to the viscosity, or do different suppliers/manufacturers tend to have their own numbering systems?

 

[Paul99]

The ISO rating (32, 46 etc) is an industry standard AFAIK so should mean you get the same viscosity no matter what supplier you use. How each manufacturers oil performs (as a hydraulic oil) however might vary greatly depending on quality of the oil itself but more importantly the quality and quantity of additives used like anti foaming compounds etc.

Since it's easy to get hold of and cheaper than standard engine oils I tend now to use it as a generic oil for nearly every odd job needing a squirt of oil from squeaking hinges to drilling lubricant and even as chainsaw oil.

 

[pedrobedro]

I put some hydraulic oil in an oil can as it was the easiest way to get it into my jack without making too much mess when topping up. I forgot about it and left it in there and when I went back to it a few weeks later it had turned into a milky substance like the oil used in cutting tools. I certainly wouldn't use it as lubricant anywhere that mattered and definitely not use it as chain oil for my saw. This was good quality oil as used by my brother in law in his JCB 3C

 

[Justme]

I dont think the 32 rating is its single viscosity rating. If I remember right 32 hydrolic oil is about the same as straight single grade 10w oil.


Its also worth noting that hydraulic oil is designed to absorb moisture as a way of protecting the hydraulic system innards. Unlike normal oil that will keep it separated.

Once it gets to max holding capacity it starts to foam / goes white. After that the extra water will form globules on the bottom of the tank.

 

[MattF]

Cheers chaps. Honestly didn't realise that it was designed to absorb moisture. I always assumed it was the complete opposite. That one's now off my list of possibilities. Looks like I'm sticking with the container dregs of unused motor oil for the time being.

 

[rory1]

Here's a chart that compares the viscosity of different types of oil

http://media.noria.com/sites/archive_images/Backup_200107_viscosity_table_2.gif

 

[Justme]

Ah, so 32 has the same viscosity as 15w not 10w.

 

[KemppiFrog]

How close is ATF to hydraulic, they do the same job in steering systems? I drained my Ford (manual) gearbox and it had ATF in it?? Is this normal?

I knew veg based brake fluid was hydroscopic, didn't realise hydraulic was too.

 

[Julian_P]

How close is ATF to hydraulic, they do the same job in steering systems? I drained my Ford (manual) gearbox and it had ATF in it?? Is this normal?

I knew veg based brake fluid was hydroscopic, didn't realise hydraulic was too.

Well I use AFT in one of my oil cans as I find it penetrates well. In cars I believe Landrover specced ATF in one of their manual boxes - nice and thin to help the gearchange.

hydraulic fluid, I don't think, is hydroscopic, I suspect some slightly wonky thinking here as it's normally the hydraulic filters that contain hydroscopic media. Here's what the web says about hydraulic fluid: Hydrolytic stability
ability of additives and certain synthetic lubricants to resist chemical decomposition (hydrolysis) in the presence of water. And: hydrolytic stability
the ability of a product to withstand chemical reaction with water to produce acids and other substances

Julian

 

[rtbcomp]

ATF is an option for my Volvo 240 gearbox.

PS - the word is hygroscopic, not hydroscopic

 

[KemppiFrog]

ATF is an option for my Volvo 240 gearbox.

PS - the word is hygroscopic, not hydroscopic

Thank you, RTB. d,s and g,s do look a bit similar

 

[gordon stephenson]

My Volvo 760 had ATF in the gearbox too,

 

[pedrobedro]

I knew veg based brake fluid was hydroscopic, didn't realise hydraulic was too.

Common brake fluid is mineral based and is hygroscopic

 

[rtbcomp]

My Volvo 760 had ATF in the gearbox too,

Mine too - but it did have an auto box!

 

[Julian_P]

Common brake fluid is mineral based and is hygroscopic

Don't think so, it's phosphate ester based. Mineral oil was used by the likes of Citroen in their wierd old cars....

Julian

 

[Pete.]

As a lubricant it does a fantastic job. i use it for all sorts of stuff in my home workshop.

I never saw any hydraulic oil turn milky just from being left standing though, it must have been contaminated with something, or it was some other oil in a hydraulic oil can.

A contractor on a site I was on once bought a can of 'hydraulic oil' cheap off some dude and put it in his 360. Turned out it was concrete ad-mixture and it trashed the whole hydraulic system. They had to scrap the machine.

 

[AndyStobbs]

Many car gearboxes (manauls) and diffs/transfer boxes use ATF. Its not uncommon.

 

[hairymel]

PS - the word is hygroscopic, not hydroscopic

what the f..

its surprising how I can travel through life confident in my hard earned knowledge and then one day find out the world is not flat