TL;DR: Near the top of the cycle, no. In Brisbane on 24 July, across the 259 supermarket sites with a cheaper independent nearby, the median supermarket board for 91 petrol was 186.9c/L; take your 4c docket off and it’s 182.9c/L. The median cheapest independent within a 4km search was 176.9c/L — still about 6c/L cheaper after the docket, around $3 on a 50L fill. The independent won at 80% of those sites, and the winner sat a median 2.5km away. At the bottom of the cycle it’s closer, and the docket can win.
The question
Someone at the op-shop counter had a Coles docket in her purse and a servo two suburbs over she reckoned was cheaper. “I’ve got 4c off on my docket, so the supermarket servo is the cheapest one for me,” she said. Is it — spend the docket, or drive the extra couple of kilometres? Everyone runs this sum in their head at the bowser, so I ran it properly.
What I checked
Every number here is the Queensland Government price feed — the board price each station reported, not a driver’s guess. Same feed that fills the map.
I took the board snapshot for Brisbane metro on 24 July: 440 stations with a live 91 price within 30km of the CBD. Then I did it pairwise, not in a lump. For every supermarket-aligned site — the chains where a Coles or Woolies 4c docket redeems — I knocked 4c off its board price. (The docket terms — 4c a litre for a $30 shop, redeemed at the one partner chain — are the supermarkets’ own, not something I’m measuring; I’ve taken them as stated.) Then I found the single cheapest independent (United, Metro, Liberty, Pearl, U-Go and Freedom) within a 4km search of it, and took the difference. Of the 289 supermarket sites on the metro board, 259 had any independent within that 4km — the other 30, about one in nine, sit isolated with nothing independent close enough to compare, so they drop out. Across the 259 matched sites, I took the median.
Pairwise matters. Comparing citywide averages would mush it. What a real driver faces is this supermarket servo against the cheaper one near it — so that’s what I measured, one site at a time.
What it shows
After the docket, the supermarket servo is still dearer at most sites.
Across those 259 matched sites the raw board gap between the two medians was 10.0c/L (186.9 down to 176.9). The docket claws back 4c of that — leaving about 6c/L in the independent’s favour. On a 50L fill that’s about $3 you’d keep by driving. And it wasn’t a fluke of a few sites: at 207 of the 259 supermarket servos — 80% — a cheaper independent still beat the docket price, and within the 4km search the winner sat a median 2.5km away. Two suburbs over, like she said.
The verdict
Near the top of the cycle, driving to the independent wins — about 6c/L, roughly $3 a fill, four times in five. The docket is a real 4c, but it’s 4c off a board that’s already sitting high, and the independents ramp less at the peak — see the independents-vs-majors piece.
It’s not a universal law, though. At 52 of the 259 sites the docket did win — isolated supermarket servos with nothing independent nearby, or a pocket where the local prices had already dropped. And this is a near-peak snapshot. At the bottom of the cycle the whole board squashes down together and that 10c gap shrinks, so a 4c docket can get you over the line. The docket looks most tempting exactly when it loses hardest — at the peak — which is the catch worth knowing.
So what for you
Don’t treat the docket as settling it. It’s 4c in your favour, not a win by default — check the cheaper servo near you before you decide, because two suburbs over is often still cheaper even after the 4c comes off. The prices on Pinly Fuel come straight off the Queensland Government feed, so the number on the map is the number on the board — knock your 4c off it in your head and compare. (If your docket only redeems at one chain, just compare that chain; the answer points the same way.)
The honest limit
Two medians here, over two different populations, so don’t mix them up. The metro-wide 91 median — all 440 stations that quoted a price, supermarkets and independents together — was 185.9c/L. The supermarket-aligned board on its own (289 sites) sat higher at 187.9c/L, which is the point: the docket chains price above the metro middle before any docket comes off. The 186.9 and 176.9 in the chart are a third thing again — the like-for-like medians across just the 259 matched sites I compared pairwise. Same feed, three honest cuts; the gap holds up in all of them.
The 176.9 is the median cheapest independent within 4km across all 259 matched supermarket sites — every site I could pair, not just the ones where the independent won. This is board price on one day near the cycle peak, and it’s the peak answer, not a year-round average — at the trough the docket closes the gap and can win. The margin also depends on how far you’ll go: widen the search past 4km and the cheapest independent tends to sit a little lower still, so a genuinely out-of-the-way servo grows the gap but costs you the drive. I didn’t model the fuel you burn on the detour, but 2.5km each way costs well under a dollar, so the $3 survives a short hop. A docket you earned by spending $30 on groceries is money already spent — that’s not a fuel saving, so I’ve left it out. The board was also rising across this week — the metro-wide 91 median sat at 175.9c/L on 20 July and 185.9c/L by the 24th on the QLD Government feed — so these are near-peak numbers, not a settled level. I ran this on 91; E10 tracks it within a cent or two most days, so the verdict doesn’t move. And this is Brisbane metro, 91 petrol, on the QLD Government feed — your local spread can differ.
— Karen