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Hydraulic Fluids · Viscosity Grade Reference
ISO VG 46 hydraulic oil is the most widely specified viscosity grade in UK industrial and mobile hydraulics, and it is the grade we hold in the most depth. Britannia Automotive & Hydraulic Lubricants Ltd stocks fifteen separate VG 46 lines across Shell, Castrol, Valvoline, TotalEnergies and Wolf, in mineral, high-VI, synthetic, biodegradable and food-safe formulations. We supply them to workshops, plant operators, distributors and industrial sites on trade terms, quoted per order.
Tell us the machine, the pack size and your delivery postcode, and we will confirm the correct grade and price the same working day.
ISO VG 46 is the default hydraulic grade for equipment operating at moderate ambient temperatures under moderate to heavy load. It is what most excavators, cranes, hydraulic presses, injection moulding machines, tipper gear and workshop lifts run on in the UK climate.
The grade earns that position because it sits in the middle of the usable range. VG 32 flows more readily on a cold start but thins too far once a system reaches working temperature under load. VG 68 holds its film better when hot but costs efficiency and makes cold starts harder. VG 46 is the compromise that suits year-round UK operating conditions, which is why OEM handbooks so often specify it as standard and list VG 32 and VG 68 only as seasonal or climate alternatives.
VG stands for Viscosity Grade, and the number is the oil’s nominal kinematic viscosity in centistokes at 40°C. The classification is set by ISO 3448, “Industrial liquid lubricants — ISO viscosity classification”, which was last confirmed in 2023 and remains current.
The number is a midpoint, not an absolute. ISO 3448 allows a deviation of plus or minus 10% of the nominal viscosity, so an oil sold as VG 46 may measure anywhere from 41.4 to 50.6 cSt at 40°C and still be correctly labelled. Each grade in the series is roughly 50% more viscous than the one below it, which is why the steps run 32, 46, 68 rather than in even increments.
There is no difference. They are the same viscosity grade written two ways, and you will see both on datasheets, drum labels and OEM handbooks interchangeably.
“ISO 46” is simply the shortened form. Where a genuine difference does appear is in the letters that follow — HL, HM, HV, HLP, HVLP — because those describe the additive package and performance class, not the viscosity. An ISO VG 46 HM and an ISO VG 46 HV have identical viscosity at 40°C but behave differently across a temperature range, and they are not automatically interchangeable in a system that specifies one of them.
Equivalence works on two axes: the viscosity grade, and the performance class. Matching only the number is how the wrong oil ends up in a machine.
| Reference | ISO VG 46 equivalent | What it actually tells you |
|---|---|---|
| Kinematic viscosity at 40°C | 46 cSt nominal, 41.4–50.6 cSt permitted | The ISO 3448 grade band |
| Approximate SAE equivalent | SAE 15W (monograde reference only) | A rough crossover, not a substitution |
| Adjacent ISO grades | VG 32 (28.8–35.2 cSt), VG 68 (61.2–74.8 cSt) | Seasonal or climate alternatives |
| ISO 6743-4 / ISO 11158 category | HM (anti-wear), HV (high viscosity index) | The additive and performance class |
| DIN 51524 designation | Part 2 = HLP, Part 3 = HVLP | The German equivalent of HM and HV |
| Current governing standards | ISO 11158:2023, DIN 51524-2:2017-06 | What a current datasheet should cite |
Two points on that last row are worth checking on any datasheet you are handed. DIN 51524-2 covers HLP oils for hydrostatic drive systems where thermal stress occurs, where water ingress makes corrosion likely, and where anti-wear additives are needed for mixed-friction conditions in pumps and motors — that scope, not the viscosity number, is what makes an oil HLP. And ISO 11158:2009 was withdrawn in October 2023 and replaced by ISO 11158:2023, which covers the same HH, HL, HM, HV and HG categories. A datasheet still quoting the 2009 edition is not necessarily wrong about the oil, but it is out of date about the standard.
We hold fifteen VG 46 lines, covering every common performance class rather than a single house grade. That range is the reason trade customers come to us for a specification match instead of a nearest-available substitute.
Adjacent grades are stocked alongside them, so a site running mixed equipment can take VG 32, VG 46 and VG 68 on one order. The full range sits in our hydraulic fluids and industrial lubricants categories, and volume buyers should start with our wholesale hydraulic oil page.
Britannia supplies ISO VG 46 hydraulic oil to UK trade customers in 5-litre, 20-litre, drum and IBC quantities, with delivery nationwide and internationally on request. We operate a quote-based model rather than an online checkout, so pricing reflects your grade, pack size and volume rather than a shelf rate.
Send us the equipment or the OEM specification, the pack size and your delivery postcode, and our team will confirm the right product and quote the same working day. If you are not certain which class your system needs — HM or HV, mineral or synthetic, standard or zinc-free — tell us the machine and we will work it out with you. Buyers ordering engine oils on the same delivery can add them from our bulk engine oil range.
Our team responds within one working day with product, specification and trade pricing confirmed.