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Instant Freight-Included Delivered Pricing on ASTM D3487 Type II Naphthenic Transformer Oil — Drums, Totes & Bulk Tankers
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What Is Mineral Type II Transformer Oil?
Mineral transformer oil is a highly refined naphthenic petroleum product used as the primary dielectric coolant and insulating fluid in power and distribution transformers. It dissipates heat generated by the core and windings, suppresses partial discharge, and protects the cellulose insulation paper from thermal degradation.
ASTM D3487 defines two grades of mineral insulating oil for transformers:
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Type I — Uninhibited mineral oil. Used in sealed or nitrogen-blanketed transformers where oxidation resistance is less critical.
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Type II — Inhibited mineral oil. Contains antioxidant additives (typically DBPC) that significantly extend service life in breathing transformers exposed to oxygen and moisture.
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Type II is the standard specification for most utility, commercial, and industrial transformer applications in North America. If your transformer draws in air during cooling cycles, Type II is the correct choice.
ASTM D3487 Type II Specifications
Property | Test Method | Type I Requirement | Type II Requirement |
|---|---|---|---|
Dielectric Breakdown Voltage (kV min) | ASTM D1816 | 30 | 30 |
Color (max) | ASTM D1500 | 0.5 | 0.5 |
Kinematic Viscosity at 40°C (cSt max) | ASTM D445 | 12 | 12 |
Kinematic Viscosity at 0°C (cSt max) | ASTM D445 | 76 | 76 |
Kinematic Viscosity at -30°C (cSt max) | ASTM D445 | 3000 | 3000 |
Flash Point (°C min) | ASTM D92 | 145 | 145 |
Pour Point (°C max) | ASTM D97 | -40 | -40 |
Neutralization Number (mgKOH/g max) | ASTM D974 | 0.03 | 0.03 |
Interfacial Tension at 25°C (mN/m min) | ASTM D971 | 40 | 40 |
Power Factor at 25°C (% max) | ASTM D924 | 0.05 | 0.05 |
Power Factor at 100°C (% max) | ASTM D924 | 0.3 | 0.3 |
Oxidation Stability — Sludge (% max) | ASTM D2440 | 0.1 | 0.01 |
Oxidation Stability — Acid (mgKOH/g max) | ASTM D2440 | 0.3 | 0.1 |
DBPC Inhibitor Content (% by weight) | ASTM D2668 | None (Type I) | 0.08 – 0.40 |
Corrosive Sulfur | ASTM D1275 | Non-corrosive | Non-corrosive |
Gassing Tendency (μL/min) | ASTM D2300 | Negative preferred | Negative preferred |
Water Content (ppm max) | ASTM D1533 | 35 | 35 |
Specific Gravity at 15.6°C (max) | ASTM D1298 | 0.91 | 0.91 |
Understanding the Key Test Properties
TransformerParts.com stocks ASTM D3487 Type II naphthenic transformer oil at multiple distribution centers across the United States. All pricing is freight-included and calculated to your delivery ZIP code in real time.
Available container sizes:
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55-gallon drums — Minimum 1 drum
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275/330-gallon totes — IBC totes for medium volume
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Bulk tanker — Full and partial tanker loads
Container Type | Capacity | Best For | Freight Method | Notes |
|---|---|---|---|---|
55-Gallon Drum | 55 gallons | Small top-offs / field service | LTL freight or FedEx Ground | Standard steel drum; UN-rated |
275-Gallon Tote (IBC) | 275 gallons | Medium volume fills | LTL freight | Intermediate bulk container; pallet-mounted |
330-Gallon Tote (IBC) | 330 gallons | Medium volume fills | LTL freight | Larger IBC; confirm with order |
Bulk Tanker | 3000–6000+ gallons | Large transformer fills / stocking | Bulk tanker truck | Contact for availability by region; freight included |
No forms. No phone calls. No waiting for a quote. Purchase online with credit card, ACH, or NET-30 terms.
Order Type-II Oil
Type I vs. Type II Transformer Oil —
What's the Difference?
The primary difference is oxidation inhibitor content. Type II oil contains DBPC (di-tert-butyl para-cresol) or a similar antioxidant that slows oxidative degradation, sludge formation, and acid buildup inside the transformer tank.
Which type should you specify?
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Breathing transformers (open conservator or dehydrating breather) — specify Type II. The oil contacts oxygen and moisture, making oxidation resistance critical.
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Sealed/pressurized transformers (positive nitrogen blanket) — Type I may be acceptable, but Type II is widely used regardless for its longer maintenance intervals.
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Retrofilling or top-off — always match the existing oil type. Mixing inhibited and uninhibited oils is not recommended.
When in doubt, specify Type II. It is the default for new transformer fills in North America.
Property | Type I (Uninhibited) | Type II (Inhibited) |
|---|---|---|
Antioxidant Additive (DBPC) | None | 0.08% – 0.40% by weight |
Oxidation Resistance | Lower | Significantly higher |
Sludge Formation Rate | Higher over time | Much lower (ASTM D2440: 0.01% max) |
Acid Number After Aging (mgKOH/g max) | 0.3 | 0.1 |
Typical Service Life | Shorter in breathing transformers | Longer in breathing transformers |
Best Application | Sealed / nitrogen-blanketed transformers | Breathing transformers (open conservator or dehydrating breather) |
ASTM D3487 Classification | Type I | Type II |
IEC 60296 Classification | Class I (uninhibited) | Class II (inhibited) |
Availability at TransformerParts.com | Limited | Yes — standard stock |
Relative Cost | Slightly lower | Standard (small premium over Type I) |
Mineral Type II Oil Brands Available
TransformerParts.com stocks ASTM D3487 Type II naphthenic transformer oil from multiple domestic distribution points across the U.S.
HyVolt
HyVolt is an inhibited naphthenic mineral transformer oil meeting ASTM D3487 Type II specifications. It is well-suited for breathing transformers requiring oxidation stability and long service life between maintenance intervals.
Hytrans-61
Hytrans is a naphthenic insulating oil meeting ASTM D3487 Type II requirements. Like HyVolt, it is formulated for use in power and distribution transformers and is suitable for both new fills and top-off applications.
CrossTrans-206
CrossTrans-206 is an inhibited naphthenic transformer oil meeting ASTM D3487 Type II and IEC 60296 specifications. It is available from distribution points serving the Central and Eastern U.S.
Note: Brand availability varies by delivery region and current inventory. TransformerParts.com will fulfill your order with the best-priced qualifying product from the nearest stocking location to your delivery ZIP.
Applications
Where Mineral Type II Transformer Oil Is Used
Mineral Type II naphthenic insulating oil is the dominant transformer fluid worldwide and is suitable for virtually all standard transformer applications:
Power Transformers
Substation power transformers up to transmission voltage. Type II is the standard fill for utility-grade equipment from 5 MVA and up.
Distribution Transformers
Pad-mount, pole-mount, and underground distribution transformers serving commercial and residential loads. The vast majority of distribution transformers in North America are mineral oil filled.
Mobile Substations
Mobile transformer units used for emergency response and grid support. Type II's wide operating temperature range makes it suitable for variable deployment environments.
Industrial Transformers
Furnace transformers, rectifier transformers, and large industrial drive transformers where mineral oil's thermal stability and dielectric properties meet application requirements.
When Mineral Oil Is Preferred Over Natural Esters or Synthetics
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Initial fill cost is lower than FR3 or MIDEL
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No retrofilling process required on existing mineral oil equipment
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Widely available from multiple domestic suppliers
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Proven performance in standard fire code environments
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Compatible with existing maintenance procedures and test labs
Fire Safety Considerations
Mineral Type II transformer oil has a flash point of approximately 145°C and a fire point above 155°C (ASTM D92). This makes it suitable for standard outdoor and indoor transformer installations in non-restricted environments.
For applications requiring higher fire safety ratings — such as transformers inside buildings, parking garages, tunnels, or areas with restricted fire risk — consider natural ester fluids (FR3, BIOTEMP) or synthetic esters (MIDEL 7131), which have flash points above 300°C and are classified as K-class or FM Global-approved fire-resistant fluids.
Environmental Considerations
Mineral transformer oil is petroleum-derived and classified as a petroleum hydrocarbon for spill reporting purposes. Releases to soil or waterways require immediate containment and cleanup under federal and state environmental regulations.
Secondary containment is required in most jurisdictions for transformers over a certain oil volume — check local codes and NFPA 70B for your installation.
For environmentally sensitive locations — near waterways, wellheads, wetlands, or public water supplies — biodegradable natural ester oils such as FR3 are often specified to reduce liability and contamination risk.
Ordering Mineral Type II Transformer Oil
from TransformerParts.com
How It Works
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Go to the oil store at transformerparts.com/oil-store
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Select Mineral Type II and your container type (drums, totes, or bulk tanker)
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Enter your quantity and delivery ZIP code
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Get instant freight-included pricing — no waiting, no phone calls
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Check out online with credit card, ACH debit, or apply for NET-30 terms
Shipping & Freight
All pricing shown is delivered to your site. Freight is included — what you see is what you pay. We ship from multiple distribution centers across the U.S. to minimize freight cost and lead time to your location.
Minimum Orders
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Drums: 1 drum minimum (55 gallons)
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Totes: 1 tote minimum (275 or 330 gallons depending on availability)
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Bulk tanker: Contact us for tanker minimums in your region
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Frequently Asked Questions
Is mineral Type II transformer oil the same as naphthenic transformer oil?
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Yes. "Naphthenic" refers to the crude oil base used in production. ASTM D3487 Type II naphthenic oil is the standard mineral insulating oil for transformers in North America. It is also referred to as mineral insulating oil, transformer insulating oil, and dielectric oil.
What does ASTM D3487 Type II mean?
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ASTM D3487 is the standard specification for mineral insulating oil used in transformers and other electrical apparatus. Type II specifies inhibited oil — meaning it contains an antioxidant additive (typically DBPC) that slows oxidative degradation and extends the oil's service life compared to uninhibited Type I oil.
Can I mix Type I and Type II transformer oil?
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Mixing is generally not recommended. Adding Type II inhibited oil to a transformer containing uninhibited Type I oil dilutes the inhibitor concentration and reduces its effectiveness. If topping off, use the same type that is already in the transformer.
How do I know if my transformer uses mineral oil or natural ester?
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Check the nameplate. Transformers filled with FR3 or other natural esters are typically labeled with the fluid type. If the nameplate is not available, the service manual or manufacturer documentation will specify. Never top off a transformer without confirming the existing fluid type.
What is the difference between mineral transformer oil and FR3?
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FR3 is a natural ester fluid derived from refined vegetable oil. It is biodegradable, has a flash point above 300°C, and extends insulation paper life compared to mineral oil. It costs more per gallon than mineral Type II. Mineral Type II is petroleum-based, lower cost, and the default for standard transformer applications.
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Can I buy mineral transformer oil by the drum?
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Yes. TransformerParts.com offers mineral Type II transformer oil in 55-gallon drums with freight-included delivered pricing. Enter your quantity and ZIP code at transformerparts.com/oil-store to get instant pricing.
What is the lead time on mineral Type II transformer oil?
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Lead times vary by region and container type. Drum and tote orders typically ship within 1–3 business days from the nearest distribution center. Bulk tanker orders may require additional lead time. Pricing and estimated delivery are shown at checkout.
Do you offer NET-30 terms?
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Yes. Qualified businesses can apply for NET-30 credit terms at checkout. NET-30 orders are processed immediately — no waiting for payment before your order ships.
Buy ASTM D3487 Type II
Transformer Oil Online
TransformerParts.com stocks ASTM D3487 Type II inhibited mineral insulating oil in 55-gallon drums, 330-gallon totes, and full tanker loads. All shipments include certificates of analysis confirming compliance with ASTM D3487 Type II requirements.
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