The named series were Mobil's lowest cost general purpose gear and bearing oils. They would be the first choice for a big old machine that looses a lot of oil. But it doesn't matter. I talked with Mobil last week and they are completely discontinuing the named series and recommend using the 20 series as a direct replacement. Probably not that many simple old machines out there anymore. I think the 20 series additives make it suitable for hydraulic systems which would have more sliding metal components and tighter tolerances than an old gearbox. I think Chevron Regal R&O oils are the same as the Mobil named series if that is what you want.
This was cross-posted to the Monarch forum. There's some very bad information here; I want to set the record straight.
- The DTE Named Series IS NOT Mobil’s “lowest cost” oil. In fact DTE Light is about 10% more expensive than DTE 24, even in 55 gallon drums. Both oils are made from turbine quality feed stock. They differ primarily in the additives used.
- The DTE Names Series HAS NOT been discontinued. It was available in December 2009 when Mad Machinist posted this and it is available today. AFIK, Mobil has no plans to discontinue it.
- Mobil DOES NOT recommend DTE 24 as a direct replacement for DTE Light. (Call their lube tech support line at 1-800-443-9966 and ask them yourself.)
Possibly he’s confused on the last two points. The Vactra Named Series was discontinued and the DTE
Named Series is the recommended replacement.
The DTE 20 series, which includes DTE 24, is formulated as hydraulic oil. The main purpose of hydraulic oil is to move things via hydraulic force, be it the cylinder on a backhoe or an industrial robot. According to the Exxon-Mobil website, the 20 series “
…were developed in conjunction with the major builders to meet the stringent requirements of severe hydraulic systems using high pressure, high output pumps as well as handling the critical requirements of other hydraulic system components such as close clearance servo-valves and the high accuracy numerically controlled (NC) machine tools.” The two companies they mention by name are Denison (a Parker Company) and Vickers (an Eaton Company); both market high end hydraulic cylinders, servo valves, etc. These components use special alloys that require protection by special additives in the oil. The NC machine tools they referr to here are probably things like industrial robots, not CNC machining centers.
Hydraulic oil has to operate in very different conditions than gear oil and has special additives to handle the service. For example, a retracting hydraulic cylinder carries minute amounts of contaminants back into the cylinder where it can contaminate the oil; special additives work to neutralize the contamination. Hydraulic systems usually have filters to remove particles from the oil and this typically means that additives are used to suspend the particles until they reach the filter.
Additives aren’t necessarily compatible with one another and may work at cross purposes. For example, the additives in DTE 24 inhibit it's ability to separate from water; DTE Light, on the other hand, has excellent water separation properties.
I’m sure DTE 24 is dandy for what it’s designed to do: operate under pressure and protect internal hydraulic components with exotic metallurgy. It has special anti-wear additives designed to meet those needs.
DTE Light is better at other things: better anti-foaming, much better water separation, better rust and oxidation protection. Foaming can definitely be a problem with a high speed spindle bearing, i.e. 10EE running at 4000 RPM.
For a machine tool spindle with no circulating pump and filter to clean the oil, the last thing you want is oil designed to suspend particles; you want the particles to settle harmlessly to the bottom of the sump. You also want water to separate completely. You don’t want water and debris constantly circulating though precision bearings. The only reason that I can think of for a machine tool manufacturer to specify DTE 24 over DTE Light in a spindle is some sort of alloys used that require the special additives. Obviously, if DTE 24 is specified, that's what you use.
data sheets:
Mobil DTE Oil Named Series
Mobil DTE 20 Series
Cal