Monthly car costs: a line-by-line example in SAR and EGP
What does your car really cost each month? Two full examples in SAR and EGP: fuel, oil, tyres, insurance, fees, and the cost people forget: depreciation.
Reviewed 8 min read
First: has consumption really gone up?
Many people go by feel (“the tank empties faster”) or the dashboard figure, and both can mislead. The feeling is coloured by a higher price per litre or more trips this month, and the dashboard number is an estimate that can be off. The right method is simple:
- Fill the tank until the pump clicks off the first time, and note the odometer.
- Drive as usual; at the next fill-up, fill to the click again and note the litres and odometer.
- Divide the litres by the kilometres and multiply by 100: that's your L/100 km.
Consumption (L/100 km) = litres at the second fill-up ÷ km between fill-ups × 100
Example: You filled up at 52,300 km. Next time the car took 42 L at 52,780 km. Distance 480 km, so consumption = 42 ÷ 480 × 100 = 8.75 L/100 km (about 11.4 km/L).
Repeat over at least three fill-ups and take the average, because a single fill-up can be skewed by a road trip or unusual traffic. If the new average is more than about 10% above your car's usual figure, there's a cause worth finding.
The causes, with numbers
These figures come from the US Department of Energy (fueleconomy.gov) and Natural Resources Canada. They're approximate and vary by car, road and weather, but they show where to start: the biggest effect and the easiest fix first.
| Cause | Extra fuel | What to do |
|---|---|---|
| Aggressive driving | worst in traffic) | Smooth starts; look ahead to anticipate lights |
| AC in extreme heat | up to 25% (short trips most) | Air out the hot cabin for a minute, then use AC; park in shade |
| 120 km/h instead of 100 | ≈ 20% | Ease off on the highway |
| Roof box or rack | 2–17% (من المدينة إلى الطريق السريع) | Take it off when you don't need it |
| Under-inflated tyres | 0.6–4% | Check pressure monthly with cold tyres |
| Wrong oil grade | 1–2% | Use the grade in your manual |
| Extra 45 kg | ≈ 1% | Clear heavy things out of the boot |
Rough figures; they vary by car, road and weather. Sources: US Department of Energy (fueleconomy.gov) and Natural Resources Canada (NRCan), 2026.
Good to know: What about the air filter? On modern fuel-injected cars, a clogged filter hurts acceleration but barely affects fuel economy, according to the US Department of Energy. Change it on schedule, but don't expect it to fix your fuel bill.
Causes the table doesn't show
If you've ruled out driving style, AC, speed and tyres and consumption is still high, the cause may be a fault. These are the usual suspects, and all need a mechanic's check:
- Check-engine light on: a faulty oxygen sensor or similar can make the engine computer add more fuel. Ask for a diagnostic scan.
- A sticking brake: one wheel much hotter than the others after a drive, or the car pulls to one side.
- Worn spark plugs or coils: shaking at idle or weak acceleration.
- A thermostat stuck open: the engine takes too long to reach normal temperature.
- A fuel leak: a smell of petrol around the car. This is dangerous; stop and have it checked at once.
Also watch for changed conditions, not just faults: moving further from work, short school runs every morning, or a longer summer all raise the average with nothing broken.
What to check, cheapest first
- Work out consumption properly over 3 fill-ups.
- Set tyre pressure to the door-sticker number.
- Remove the roof rack and empty the boot.
- Try two weeks of calm driving and lower highway speed, then compare.
- Make sure the oil is the right grade and the service is up to date.
- If the gap stays, get a diagnostic scan and have the brakes and plugs checked.
Read next: How often to change engine oil · Tyre age and date code
What does the difference cost you each month?
Example: a car that averaged 8 L/100 km now uses 9.6, a 20% rise, and covers 2,000 km a month. That's 32 extra litres a month. At SAR 2.33 a litre, the October 2026 price of 95 in Saudi Arabia (Saudi Aramco), that's about SAR 75 a month, nearly SAR 900 a year. In Egypt at an example EGP 19.25 a litre (an illustration, not today's price) it's about EGP 616 a month. The current price is in the box alongside.
Let Sayarti+ watch your consumption
Log each fill-up in three fields (odometer, litres, price or amount), and Sayarti+ works out consumption full tank to full tank, even with partial fill-ups or one you forgot to log, and charts every fill-up. A sudden jump in the chart flags a problem before it costs you much. For company cars, Sayarti+ Business alerts you when a car uses clearly more than its usual average.
Read next: Fuel consumption sheet for company cars
FAQ
What makes a car use more fuel?
Most often: aggressive driving in traffic, AC in heat, high speed, a roof rack and low tyre pressure. Then faults such as sensors or sticking brakes.
How do I know consumption really went up?
Calculate full tank to full tank over 3 fill-ups and compare with your usual average. More than about 10% higher is worth investigating.
Does AC use a lot of fuel?
In extreme heat it can add up to 25%, most on short trips. On the highway, AC is better than open windows.
Does a new air filter save fuel?
On modern fuel-injected cars, usually not, according to the US Department of Energy. It helps acceleration, so change it on schedule.
How can I cut my car's fuel use?
Drive smoothly, keep highway speed moderate, keep tyres at the right pressure, remove the roof rack, service on time, and cut idling.
Why does the dashboard differ from my maths?
The dashboard figure is the car computer's estimate and can be a few percent off. Full-to-full maths is more accurate because it uses the actual litres.
Sources
- US Department of Energy (fueleconomy.gov): Keeping your vehicle in shape; tyre pressure, oil grade, air filter on modern engines — checked 28 October 2026
- US Department of Energy (fueleconomy.gov): Driving more efficiently; aggressive driving costs 10–40%, roof cargo and extra weight — checked 28 October 2026
- US Department of Energy (fueleconomy.gov): Fuel economy in hot weather; AC can cut economy by more than 25% on short trips — checked 28 October 2026
- Natural Resources Canada: Fuel-efficient driving techniques; 120 km/h uses about 20% more than 100 km/h — checked 28 October 2026
- Saudi Aramco: Fuel prices, October 2026; gasoline 91 SAR 2.18, 95 SAR 2.33 per litre — checked 28 October 2026
We write practical guides on car costs, maintenance and company cars. Every number has a source.
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