Mobiltherm oils are important members of the Mobil brand of specialty fluids that have gained a reputation for performance and reliability, even in severe applications. Modern refining techniques are a key factor in providing the excellent product features.

Mobiltherm 600 Series offer the following benefits:

Features Advantages and Potential Benefits
High resistance to thermal cracking and decomposition Free from sludge and coke deposits and minimum interference with heat transfer capability and minimized maintenance needs
Excellent thermal properties High heat transfer rates and improved operating efficiency and lower operating costs
Good thermal and oxidative stability Long trouble free service life and reduced downtime
Good low temperature fluidity Easy starting of cold systems


Application Considerations: Mobiltherm heat transfer oils should not be mixed with other oils since this may impair the excellent thermal and oxidation stability resulting in a change in other properties, and complicate analyses aimed at determining useful oil life. If the oils are used above their recommended maximum temperatures, vapor lock may result unless the system is designed to operate at the higher temperature by pressurizing with an inert gas such as nitrogen. At higher temperatures, fluid life will be shortened because the rate of thermal degradation which increases markedly as temperatures rise above the recommended limit. In well-designed systems the temperature of the oil film surrounding the heating element should be about 15ºC to 30ºC above the bulk oil temperature. If higher than this, the service life of the oil may be shortened and sludge and coke may be deposited which would interfere with the heat transfer rates.

As with other mineral oils, Mobiltherm heat transfer oils should be used only in systems with forced circulation. Systems that depend on convection for circulation of the heat transfer medium do not provide a rapid enough flow to prevent local overheating and rapid deterioration of the oil. Further, these oils are not recommended for use in open systems where hot oil is exposed directly to the air. If they spray or escape from leakage points, hot Mobiltherm oils may spontaneously ignite.

Mobiltherm 600 series can be used in open and closed installations where the bulk oil temperature ranges are as outlined in the table below.

  • Mobiltherm 603: Closed Systems (-15º C to 285º C), Open Systems (-15º C7 C to 150º C)
  • Mobiltherm 605: Closed Systems (-12º C to 315º C), Open Systems (-12º C to 180º C)
  • Mobiltherm 610: Open systems (-6°C to 250°C)
  • Mobiltherm 611: Open systems (-6°C to 275°C)

Typical Properties

Mobiltherm 600 Series 603 605 610 611
Viscosity, ASTM D 445
cSt @ 40ºC 20.2 30.4 113 490
cSt @ 100ºC 4.2 5.4 11.5 31.5
Pour Point, ºC, ASTM D 97 -15 -12 -6 -6
Flash Point, ºC, ASTM D 92 194 230 250 294
Specific Gravity @15 ºC kg/l, ASTM D 4052 0.835 0.857 0.88 0.906


5.0 / 5.0
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1 Star
If only all companies operated like this one.
Did a little research and found the best price with this company. Never ordered from them before so I didn’t know what to expect service wise but was shocked at how quickly I received my order and the packaging was excellent as well. It was such a breeze to order and completely hassle free. Definitely will use them in the future.
Needed mobiltherm for my carpet cleaning  truck
Needed mobiltherm for my carpet cleaning truck
December 18, 2018
1 year ago
Great Customer Service
We use this oil in a closed system for heating. It has a great lifespan. The Lubricant Store had the best price I could find unless I wanted to buy a 55 gallon drum which would have been overkill for our needs. The buckets were on back order, but thankfully they were able to ship out a partial order and got everything here as quick as possible. Sylvanie was the excellent rep who helped me. She was responsive and accommodating. She made my experience great.
April 2, 2019
1 year ago


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Browse 3 questions Browse 3 questions and 12 answers
Why did you choose this?
The Lubricant Store Store
For thermal transfer
Bryan W on Jan 20, 2020
Needed for project
Kirk V on Aug 30, 2019
For thermal transfer
Bryan W on Jan 20, 2020
I picked this product because it's exactly what I need.
Joe K on Oct 14, 2019
Needed for project
Kirk V on Aug 30, 2019
for equipment
Rachel C on Aug 22, 2019
RICKY B on Jul 10, 2019
Required by our Maint dept.
Richard C on May 30, 2019
Spec's fit my needs
Charles E on May 17, 2019
customer request
Alejandro T on Mar 14, 2019
Quick and easy ordering and checkout on-line. This is a required product for our machine and most suppliers only have drums. The Lubricant Store has 5 gallon pails, good for us when we are filling machine.
I needed it.
Alexander B on Aug 15, 2018
I picked this product because it's exactly what I need.
Joe K on Oct 14, 2019
for equipment
Rachel C on Aug 22, 2019
can i use mobiltherm 43 in place of 603?
pomaxp22 on Jun 8, 2018
BEST ANSWER: The Mobiltherm 43 is more like and comparable to the Mobiltherm 605 not the 603. The 605 is closer in performance to Mobiltherm 43 and has better low temp capabilities with the 605.
can this be used on a radiant floor heat system?
A shopper on May 10, 2018
BEST ANSWER: Potentially yes, however, we don't know how intense the heat is and we don't know if it's compatible with the piping being used. If you are needing more information please email customerservice@thelubricantstore.com with answers to those questions.