Shell Diala S4 ZX-I – 209 Litre
Genuine Shell Diala S4 ZX-I (formerly Diala S3 ZX-IG), premium inhibited GTL transformer oil to IEC 60296 Ed.5 Type A, 209 litre drum. Authorised Shell distributor. Request a quote.
Genuine, manufacturer-sealed stock. Tell us the pack size and delivery address and we reply with price and lead time.
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Shell Diala S4 ZX-I is Shell’s premium inhibited electrical insulating oil, and this is the genuine 209 litre drum supplied by Harlow Lubricants as an authorised Shell distributor. It is the current name for the product previously sold as Shell Diala S3 ZX-IG.
Genuine, sealed Shell stock. Manufacturer data sheet and certificate of conformity supplied with every order.
Shell Diala S4 ZX-I – product summary
| Product | Shell Diala S4 ZX-I |
| Previous name | Shell Diala S3 ZX-IG |
| Type | Premium inhibited electrical insulating oil, GTL (gas-to-liquid) base |
| Specification | IEC 60296 Edition 5 (2020) Type A; IEC 60296 Ed.4 (2012) Table 2 Transformer Oil (I), Section 7.1 |
| Pack sizes | 209 L drum (this page), 20 L, bulk delivery |
| Shell part number | Confirm on quote |
| Supplied by | Harlow Lubricants Supplies, authorised Shell distributor, London NW4 |
What makes Shell Diala S4 ZX-I different from a conventional transformer oil?
Conventional transformer oils are naphthenic mineral oils refined from crude. Shell Diala S4 ZX-I is made from base oils produced by Shell’s GTL process, which gives a uniform molecular structure and essentially zero sulphur — Shell’s data sheet reports total sulphur below the 1 ppm detection limit of ASTM D5185 against an IEC limit of 500 mg/kg.
That matters because sulphur is the root of oil-related copper corrosion, a recognised failure mechanism in power transformers. With sulphur effectively absent, the oil passes the corrosive sulphur tests — DIN 51353, ASTM D1275, ASTM D1275B and the more severe IEC 62535 — as non-corrosive. The oil is also free from PCBs, DBDS and metal passivators, and is readily biodegradable.
What are the key test figures?
Typical values from the Shell technical data sheet, against the IEC 60296 Table 2 and Section 7.1 limits:
| Property | Method | IEC limit | Typical |
| Breakdown voltage, untreated | IEC 60156 | min. 30 kV | 60 kV |
| Breakdown voltage, after treatment | IEC 60156 | min. 70 kV | 75 kV |
| Dielectric dissipation factor @ 90°C | IEC 60247 | max. 0.005 | <0.001 |
| Water content (drums/IBC) | IEC 60814 | max. 40 mg/kg | 6 mg/kg |
| Total sulphur | ASTM D5185 | max. 500 mg/kg | <1 mg/kg |
| Total acidity after 500 h / 120°C | IEC 61125 C | max. 0.3 mg KOH/g | 0.02 mg KOH/g |
| Sludge after 500 h / 120°C | IEC 61125 C | max. 0.05 %m | <0.01 %m |
These are typical production values, not guaranteed minima. We send the current manufacturer data sheet with every quote so you can check against your own specification.
Which transformer manufacturers accept it?
Shell lists DOBLE TOPS and ENGIE Laborelec among its approvals, with manufacturer specifications including Hitachi Energy, HYOSUNG, SGB-SMIT and Siemens. Approval lists change, so if your OEM or utility specification names a particular body, send it with your enquiry and we will confirm against the current data sheet before quoting.
What is it used for?
Power and distribution transformers of all types, including highly loaded units and transformers in environmentally sensitive locations where the readily biodegradable formulation is an advantage. The good low-temperature viscometric behaviour means heat transfer stays effective from cold start, which matters for outdoor substation plant.
Pack sizes, price and delivery
This page is the 209 litre drum. We also supply 20 litre for top-up work and bulk road tanker delivery for transformer filling and multi-site programmes. We do not publish prices because transformer oil moves with base oil markets and depends on volume and destination — send quantity and delivery address for a current price with stock and lead time. We deliver across the UK and export to Nigeria, Ghana, Kenya and South Africa. See the full transformer oil range.
