The Department of Mineral and Petroleum Resources published the September adjustment on 31 August. From Wednesday 2 September, diesel at 0.05% sulphur (500ppm) rises 294 cents a litre and diesel at 0.005% sulphur (50ppm) rises 315 cents. Petrol 93 and 95 both rise 134 cents.
Inland wholesale diesel goes to R29.11 for 500ppm and R30.05 for 50ppm. Coastal goes to R28.24 and R28.79.
Stack that on 5 August, when 500ppm rose 138.44 cents and 50ppm rose 123.44 cents. Across four weeks the freight fuel line has moved R4.32 on 500ppm and R4.38 on 50ppm. Petrol over the same two adjustments is up 82 cents, because it fell 52 cents in August before rising 134 in September.
Benchmark your cost per drop against the headline petrol number and you will understate what happened to your business by a factor of five.
Where the September number came from
The department's own breakdown is specific, and it is worth reading rather than the summary.
International product prices added 321.29 c/l to the basic fuel price of diesel. Brent averaged $87.88 over the review period against $82.37 in the previous one, on US-Iran escalation, uncertainty over flows through the Strait of Hormuz, and higher shipping costs. Russian supply disruption held global product inventories down at the same time.
The rand moved in your favour and it was nowhere near enough. It strengthened from R16.46 to R16.21 against the dollar, taking 29.06 c/l off the diesel basic fuel price. Set against a 321 cent product move, a 29 cent currency benefit is noise.
For comparison, petrol took only 127.79 c/l from international product prices. Diesel took two and a half times as much. This is a middle distillate problem, and middle distillates are what your fleet runs on.
The line that reversed
The slate levy is the part of this adjustment that most coverage will skip, and it is the part that should change your planning.
In August the slate levy fell 52.56 c/l, from 113.94 to 61.38. That single movement is why the August diesel increase came in at R1.38 rather than closer to R1.90. It absorbed part of the product price move before it reached the pump.
In September it went the other way. The slate levy rises 21.90 c/l, from 61.38 to 83.28, effective 2 September. The cumulative slate balance stood at negative R9.519 billion for petrol and diesel at the end of July, against negative R7.418 billion at the end of June. The Self-Adjusting Slate Levy Mechanism is recovering that shortfall through the price structure.
So the September figure carries a 321 cent product move with nothing underneath it, plus 21.90 cents of recovery added on top.
Plan the next two adjustments on the assumption that the levy keeps recovering rather than releasing. A R9.5 billion negative balance does not clear in a month, and the balance grew by R2.1 billion in July alone.
One footnote for anyone modelling petrol separately: the Minister approved a 4.9 c/l increase, from 315.1 to 320.0, to cover the MIBCO forecourt wage settlement. That sits in the petrol structure only and does not touch diesel.
The line item almost nobody reprices
Fleet size, route plan and rate card all get attention when diesel moves. Cube does not appear as a line on any invoice, which is how it survives fuel increases unexamined.
Every cubic metre of air in an outbound carton and on an outbound pallet is moving at Wednesday's price. That air was decided at the packing station and at the pallet build, against box selection and stacking rules that in most South African operations were set years ago and have not been reviewed since.
Optioryx publishes three figures for its Pulse 3D Cartonization module: 15% lower shipping costs, 30% less carton used, and 35% less air shipped. Its 3D Palletization module builds full, stable pallets and returns a pallet count at order entry rather than after the fact.
Treat those percentages as direction rather than a promise for your building. The number that matters is in your own data and takes about a week to get: average fill percentage per outbound carton type and per pallet, against the theoretical maximum for the same order lines.
If that gap is 5%, leave it alone. If it is 25%, you are funding it on every drop against a R29.11 wholesale base.
How this fits alongside your existing WMS
Pulse connects on top of your existing WMS through an API. Optioryx states plainly that it is not a WMS and does not replace one. Integration runs three ways: manual file import and export, flat files over CSV or SFTP, or a direct API into your WMS, TMS or ERP.
That matters commercially. A cartonization change does not require you to reopen a WMS contract, retrain the floor on a new system, or push a capital request through an April cycle. The incumbent system keeps doing what it does, and Pulse changes how the packing and stacking decisions get made inside it.
The modules run on their own or together. Pick covers routing and clustering, published at 20% higher picking productivity and 40% shorter walking distances. Slot covers slotting beyond static ABC, at 15% higher storage utilisation and 20% lower labour cost. Pack is 3D Cartonization. Stack is 3D Palletization. Optioryx reports 65 or more warehouses live across 28 countries and holds ISO 27001 certification.
For a South African distributor the highest-value cartonization application is usually pick-to-box. The correct box type is assigned at order release, items go straight into the destination carton during picking, and repacking leaves the process entirely. The second is shipping cost visibility at order entry, which lets a sales team quote delivery on the real packed configuration rather than a nominal weight band. Optioryx's own published customer story here is Voltex, an electrical accessories manufacturer running pick-to-box across its Australian and New Zealand sites.
Three things worth doing before the October freight bill
None of these needs capital, and all three fit inside a fortnight.
- Reprice on the correct grade. Check which diesel grade your fleet and your contracted hauliers actually buy. The gap between the two September increases is 21 cents a litre, and the gap between the two inland wholesale prices is 94 cents. A fuel model built on the wrong grade is wrong by roughly 3% before it starts.
- Measure fill before you renegotiate anything. Pull 3 months of outbound consignments. For each carton type and each pallet configuration, compare the cube actually shipped against the cube the order lines needed. That single query tells you whether your cube problem is worth an intervention or worth ignoring.
- Check what your rate card is indexed to. Many South African road freight contracts carry a fuel escalation clause tied to a specific grade and a specific reference date. A 294 cent move will trigger clauses that a 138 cent move did not. Read yours before your carrier does.
The timing
Black Friday is 27 November, which is 12 weeks out. Peak outbound runs at 3 to 4 times normal volume, and every one of those consignments moves at the new base.
A cube problem that costs you a rounding error in September costs you materially in the last week of November, on volume you cannot reduce and at a fuel price you do not control. The box selection rules are the part you do control, and they can be changed without a capital request or a new WMS contract.
Measure the fill gap first. If it is small, spend your attention elsewhere.
Get the outbound cube query
It runs off 3 months of consignment history and your carton master. About a week to a number you can act on.
Sources
- Here is the official petrol price for September, BusinessTech, 31 August 2026
- Petrol and diesel up in September: Here's what you'll pay, The Citizen, 31 August 2026
- Fuel prices, Department of Mineral and Petroleum Resources
- 3D Cartonization Software for Box Packing, Optioryx
- Warehouse Optimization Software, Optioryx
Diesel prices quoted are wholesale. Pump prices differ.