Is that R40 special worth the extra drive?

A R40 discount can disappear before you reach the till. If getting it means an extra drive, compare the saving with the cost of that detour before leaving home.

Here is a fuel-only check you can do with a calculator. All the numbers below are fictional examples, not current petrol prices, retailer offers or typical car consumption.

The R40 saving that vanishes

Suppose the same groceries cost R40 less at another shop. Reaching it adds 20 kilometres to your journey, including the return. For this example, your car uses 8 litres per 100 kilometres and fuel costs R25 per litre.

  • Extra fuel: 20 × 8 ÷ 100 = 1.6 litres.
  • Extra fuel cost: 1.6 × R25 = R40.
  • Saving left: R40 discount − R40 fuel = R0.

Add a fictional R10 parking charge that you would otherwise avoid, and the cheaper basket leaves you R10 worse off. You have also spent time travelling and shopping.

Count the extra distance

If you are already going past the shop, the answer can change. With the same fictional consumption and fuel price, an extra 4 kilometres uses 0.32 litres and costs R8. The R40 discount then leaves R32 before any other extra costs.

Use the distance added by changing your route. For a separate outing from home, count the outward and return journeys. For a stop on an existing trip, compare the total route with the stop against the route you would otherwise take.

Use your own numbers

  1. Compare the same items, pack sizes and quantities. Count only purchases you planned to make.
  2. Work out the additional kilometres.
  3. Multiply those kilometres by your car's fuel consumption in litres per 100 kilometres, divide by 100, then multiply by your actual price per litre.
  4. Subtract that fuel cost, extra parking and tolls from the basket saving.
  5. Check the offer's dates, participating branch, stock, loyalty requirements and minimum spend before setting off.

The result is an estimate. Use consumption that reflects your driving where possible; a different route or traffic conditions can change it.

Fuel is only the first check

A positive result does not prove the trip is worthwhile. This calculation leaves out vehicle wear, maintenance and the value of your time. The Automobile Association explains the wider costs of running a car; its article is from 2020, and we have not used its old rand examples.

If you are browsing promotions, FreeHub's coupons and deals directory links to offer details and sources. Confirm the final terms with the retailer, then do the journey calculation. This blog is connected to FreeHub.

Sources and links checked on 7 October 2026. The worked examples are our own arithmetic, with no guaranteed saving or recommendation to make a particular purchase.

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