OP
DieselPower
Elite Member
- Joined
- Sep 30, 2006
- Messages
- 2,756
- Location
- Fairfield, PA
- Tractor
- JD 3020, JD 4230, JD 7410, JD 2440, MF 750, NH LS170
Ok, still seems to be some question about viscosity and which would work better a single viscosity or a multi-viscosity. I can probably use a real life example as the best reference.
This tow truck belongs to one of my best friends. As tow trucks go it has a rather unique hydraulic system on it. It has a one piece tripple pump instead of the regular style one piece double pump that would be found on most tow trucks this size. Two pump at the same preasure and the third pumps at a reduced preasure and operates only the winch's. Unlike most tow trucks that come with ISO 32 / SAE 10 oil as the factory fill this one came with and called for a ISO 68 due to the pump design. It was a new new tow truck body for ATAAC that year. He got finished building the truck in the spring of 2005 and it worked like a charm. As winter approached and the temps dropped however he started to notice greatly reduced speeds in his winch's and slow operations of all the hydraulic's for the first 20 or so minutes. Not exacly what you want in the dead of winter when your trying to winch trucks 250+ feet back onto a road out of a field. My answer to the problem for this truck was to replace the single viscosity hydraulic oil with a 10W/20 UTF. He changed out the fluid at some point in the summer of 2006 and during last year's and this year's winter he has had no problems.
So, what happened, why and what did the fluid change do for it to fix the problem.
The problem was that the Vickers pump that is on the truck is a industrial pump that usually uses a ISO 68 / SAE 20 viscosity hydraulic oil. In industry this type of pump would purr along all day long just fine since it's probably indoors and operates at a constant temperature. In this application however the pump is exposed to large temperature operating ranges. When it's -5 degree's outside it may take the system 20+ minutes to warm up enough to work suitably.
By replacing the single viscosity with a multi-viscosity oil the oil act's like a lower viscosity single weight oil would in the cold and as it warms up act's like a higher viscosity single weight oil would. So as far as the pump know's when it's very cold it thinks it has a 10 weight oil in it and when it warms up it thinks has a 20 weight oil in it. The pump doesn't know it's being tricked by some fancy act of chemistery.
Now let's look at Power Trac. If I had to guess the reasoning behind using 10W30 or 10W40 motor oil in their systems it would be this. We have covered the it's cheap and readily available aspect. Well if that's all they wanted they could have filled it with a single viscosity motor oil. I would have to say the reason they spec a multi-viscosity oil is to ensure peak operating characteristics in a broad temperature range. Since this system from my understanding can run rather hot they didn't want to put a thin single viscosity oil in because it would suffer at higher temps. Conversely if they had put in a higher single viscosity oil it would run very slugishly at low start up temps. What's the best of both worlds, multi-viscosity.
JJ - You wrote: "All I really want to know, what is the best synthetic single weight hydraulic oil for me here in Florida."
If your confident that your only going to be working on the warm side and start up and cold weather opertion characteristics are not a concern then the best single viscosity would probably be something like a ISO 68 or possibly even a ISO 100. The problem is until the system warms up to full operating temp it's probably going to be a little on the thick side and therefore slugish/slow. Hot operating temps would be just fine. If you go with something like a ISO 32 you would be fine when cold but once you reach full operating temp's it would be to thin. My whole reason for a multi-viscosity UTF and not a single viscosity hydraulic oil.
This tow truck belongs to one of my best friends. As tow trucks go it has a rather unique hydraulic system on it. It has a one piece tripple pump instead of the regular style one piece double pump that would be found on most tow trucks this size. Two pump at the same preasure and the third pumps at a reduced preasure and operates only the winch's. Unlike most tow trucks that come with ISO 32 / SAE 10 oil as the factory fill this one came with and called for a ISO 68 due to the pump design. It was a new new tow truck body for ATAAC that year. He got finished building the truck in the spring of 2005 and it worked like a charm. As winter approached and the temps dropped however he started to notice greatly reduced speeds in his winch's and slow operations of all the hydraulic's for the first 20 or so minutes. Not exacly what you want in the dead of winter when your trying to winch trucks 250+ feet back onto a road out of a field. My answer to the problem for this truck was to replace the single viscosity hydraulic oil with a 10W/20 UTF. He changed out the fluid at some point in the summer of 2006 and during last year's and this year's winter he has had no problems.
So, what happened, why and what did the fluid change do for it to fix the problem.
The problem was that the Vickers pump that is on the truck is a industrial pump that usually uses a ISO 68 / SAE 20 viscosity hydraulic oil. In industry this type of pump would purr along all day long just fine since it's probably indoors and operates at a constant temperature. In this application however the pump is exposed to large temperature operating ranges. When it's -5 degree's outside it may take the system 20+ minutes to warm up enough to work suitably.
By replacing the single viscosity with a multi-viscosity oil the oil act's like a lower viscosity single weight oil would in the cold and as it warms up act's like a higher viscosity single weight oil would. So as far as the pump know's when it's very cold it thinks it has a 10 weight oil in it and when it warms up it thinks has a 20 weight oil in it. The pump doesn't know it's being tricked by some fancy act of chemistery.
Now let's look at Power Trac. If I had to guess the reasoning behind using 10W30 or 10W40 motor oil in their systems it would be this. We have covered the it's cheap and readily available aspect. Well if that's all they wanted they could have filled it with a single viscosity motor oil. I would have to say the reason they spec a multi-viscosity oil is to ensure peak operating characteristics in a broad temperature range. Since this system from my understanding can run rather hot they didn't want to put a thin single viscosity oil in because it would suffer at higher temps. Conversely if they had put in a higher single viscosity oil it would run very slugishly at low start up temps. What's the best of both worlds, multi-viscosity.
JJ - You wrote: "All I really want to know, what is the best synthetic single weight hydraulic oil for me here in Florida."
If your confident that your only going to be working on the warm side and start up and cold weather opertion characteristics are not a concern then the best single viscosity would probably be something like a ISO 68 or possibly even a ISO 100. The problem is until the system warms up to full operating temp it's probably going to be a little on the thick side and therefore slugish/slow. Hot operating temps would be just fine. If you go with something like a ISO 32 you would be fine when cold but once you reach full operating temp's it would be to thin. My whole reason for a multi-viscosity UTF and not a single viscosity hydraulic oil.
