How a strait you will never see reaches your fuel bill

Crude oil drops sharply. The news says so. Nothing happens at the pump, or so little that you have to check the receipt to be sure.

The usual explanation is that someone is pocketing the difference. The actual explanation is duller and more useful: most of what you hand over at a pump was never linked to oil in the first place, so most of it cannot fall when oil does.

Where the price you pay is decided

India does not produce most of the crude it uses. Import dependency for crude oil, measured against petroleum-products consumption, was 87.8% in 2023-24, and 88.1% over April to December of 2024-25. That is the Petroleum Planning & Analysis Cell's own figure, and it means the input price is set somewhere else — in dollars, on water, by people who have never heard of your city.

A large part of that oil leaves the Persian Gulf through the Strait of Hormuz, which the U.S. Energy Information Administration describes as the world's most important oil transit chokepoint. A channel a few tens of kilometres wide is therefore upstream of your commute. That is the part of the story that sounds dramatic.

The part that decides your bill is the next step.

The build-up

A pump price is assembled in layers, and only the bottom layer has anything to do with oil.

Take a build-up of ₹35 base, ₹20 excise, ₹4 commission and 25% VAT. These are illustrative figures, not current rates — the point is the shape, and you should put your own in.

That comes to (35 + 20 + 4) × 1.25 = ₹73.75 a litre.

Now let crude fall 20%, and assume every paisa of that is passed on. The base goes from ₹35 to ₹28. Excise does not move — it is a rupee amount, and it does not know what oil did. The commission does not move either. So:

(28 + 20 + 4) × 1.25 = ₹65.00

The pump price fell ₹8.75, which is 11.86% — not 20%. Of the oil move, about 59% reached you.

Nothing was pocketed. Tax was 47.1% of that original price and the crude-linked part only 47.5%, so barely half the price could respond at all.

The part almost nobody expects

Raise the excise and the pump becomes less sensitive to oil, not more.

Keep everything else the same and set excise to ₹40. Now the price before the oil move is (35 + 40 + 4) × 1.25 = ₹98.75, and after the same 20% fall it is (28 + 40 + 4) × 1.25 = ₹90.00.

The fall is ₹8.75 again. Exactly the same rupees — but now only 8.86% of the price, so the pass-through has dropped from 59% to 44%.

The rupees are identical because only the base moved, and a percentage tax scales whatever sits beneath it:

₹7 of base times 1.25 is ₹8.75, whatever the excise happens to be. The excise only changes what that ₹8.75 is a percentage of.

There is a second surprise hiding in the same formula. Raising VAT raises the price you pay, but it does not change what share of an oil move reaches the pump — because it scales both the before and the after equally. Only the rupees-per-litre components dilute the pass-through. You can check both claims with the formula above: set excise to zero and move VAT, and the pass-through figure will not budge.

Where it goes after the pump

Diesel is not mainly a household purchase. It is a freight input, and freight sits inside the price of anything that has to be carried to the place it is sold. That is the route by which an oil move becomes a grocery-bill move, arriving later and smaller, diluted at every step by the same taxes and margins.

Which matters for your money in a way that has nothing to do with driving. A fixed deposit paying 7% against 6% inflation is not earning 1% — it is earning 0.94%, because returns and prices both compound and you have to divide rather than subtract. That arithmetic is worked through in real returns — why you divide, not subtract, and you can run your own numbers on the inflation calculator or check a deposit on the FD calculator.

What this explanation does not cover

• Timing. Retail prices move on their own schedule, not on the day crude does. Everything above compares two states of the world, not the path between them.
• The exchange rate. Crude is bought in dollars. The rupee can undo a dollar-price fall entirely, and none of the arithmetic here shows that separately.
• Whether a move is passed on at all. That is a commercial decision, which is why the simulator makes it a slider you set rather than a number anyone hands you.

The honest summary is narrow and worth holding on to: whenever a fixed rupees-per-litre charge sits in a price, a percentage move in the underlying commodity always arrives smaller. Not because of anyone's motives — because of the shape of the sum.

Which industries sit at the other end of these routes, and what depends on which strait, is a larger question than one article can settle — and one worth reading the shipping and customs sources on directly.