Shell Diala S4 ZX-I – 20 Litre
Genuine Shell Diala S4 ZX-I (formerly Diala S3 ZX-IG), premium inhibited GTL transformer oil to IEC 60296 Ed.5 Type A, 20 litre. 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 20 litre pack 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. The 20 litre is the practical size for topping up, commissioning small units and maintenance work where a 209 litre drum is more oil than the job needs.
Genuine, sealed Shell stock. Manufacturer data sheet and certificate of conformity supplied with every order.
Shell Diala S4 ZX-I 20 L – 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 | 20 L (this page), 209 L drum, bulk delivery |
| Shell part number | Confirm on quote |
| Supplied by | Harlow Lubricants Supplies, authorised Shell distributor, London NW4 |
Why specify a GTL-based insulating oil?
Shell Diala S4 ZX-I is made from base oils produced by Shell’s gas-to-liquid process rather than refined from crude. The result is a uniform molecular structure and essentially zero sulphur — below the 1 ppm detection limit of ASTM D5185, against an IEC limit of 500 mg/kg.
Sulphur is what drives oil-related copper corrosion inside a transformer, so removing it removes that risk. The oil is non-corrosive to DIN 51353, ASTM D1275, ASTM D1275B and IEC 62535, free from PCBs, DBDS and passivators, and readily biodegradable.
Can I use a 20 litre pack to top up an existing transformer?
Only if it matches what is already in the tank. Diala S4 ZX-I is an inhibited oil; mixing inhibited and uninhibited fills, or mixing across base oil types, should be assessed before you do it rather than after. If you are unsure what is in the unit, have the existing oil sampled first. We can quote either an inhibited or an uninhibited grade once you know.
Key test figures
Typical values from the Shell data sheet: breakdown voltage untreated 60 kV against an IEC 60156 minimum of 30 kV; dielectric dissipation factor at 90°C below 0.001 against a maximum of 0.005; water content 6 mg/kg against a maximum of 40 mg/kg for drums and IBCs. After 500 hours at 120°C the oil shows total acidity of 0.02 mg KOH/g and sludge below 0.01 %m. These are typical production figures — the current data sheet goes out with the quote.
Pack sizes, price and delivery
This page is the 20 litre. For larger volumes see the 209 litre drum or bulk delivery. Prices are not published; send quantity and delivery address for a current price with stock and lead time. UK delivery and export to Nigeria, Ghana, Kenya and South Africa. See the full transformer oil range.
