Fuel is the heart of engine performance. When a vehicle stands idle, it is first the petrol that degrades: loss of octane, oxidation, moisture absorption in petrol containing ethanol, and formation of deposits. This guide gathers only the good practices related to fuel, to avoid hard starts and damage to fuel-system components.
1) Petrol shelf life: practical guidelines
- SP95 / SP98: 3 to 6 months recommended without driving (beyond that: lower octane rating and volatility).
- SP95-E10: ~3 months, because ethanol is hygroscopic (it absorbs moisture from the air).
- Low-ethanol SP98 + stabiliser: up to 9–12 months with careful storage (tank tightly closed, dry and temperate environment).
Fuel warning signs: acrid/solvent-like smell, brownish colour, engine that stutters, stalling, unusual knocking.
2) Why does petrol degrade?
- Oxidation: petrol reacts with oxygen and loses its volatility and its anti-knock power.
- Gums and varnishes: polymerisation of certain fractions → deposits in the injectors/carburettor and the pump.
- Water/condensation: especially with E10; micro-droplets → corrosion, misfires and hard starts.
3) Before storage: 100 % fuel checklist
- Fill up to ~95 % to limit the volume of air and therefore condensation in the tank.
- Add a fuel stabiliser (follow the dosage) then drive 10 km to spread the product as far as the injection rail.
- Prefer SP98 for a long stop (less ethanol). SP95-E10 requires more vigilance.
- Seal tightly (cap, compliant venting) and store away from heat and humidity.
4) During storage: what to do about the fuel?
- Monthly maintenance start (10–15 min) to renew the petrol in the circuit and prevent gums.
- Smell check: a strong rancid/solvent smell may indicate advanced oxidation.
- Avoid opening the tank unnecessarily (air exchange = potential moisture).
5) Back on the road: fuel protocol
- Inspection: look for abnormal smells, check tightness and the condition of the hoses.
- Fuel age:
- ≤ 3 months (SP/E10): generally fine if stabilised and stored correctly.
- 3–6 months: consider a 50/50 dilution with good-quality fresh fuel.
- > 6–9 months (E10) or > 12 months (SP98/stabilised): favour draining the tank and replacing the petrol filter.
- Filtration: replace the filter if misfires/knocking appear after the top-up.
- First start: let it stabilise at idle and listen for knocking (a sign of insufficient octane). If needed, add a temporary octane booster.
- Fresh fill-up as soon as possible to flush the old fuel out of the circuit.
6) E10 vs SP98: which to choose when storing?
For prolonged storage, SP98 is generally more stable (low ethanol content) and limits water absorption. SP95-E10 remains usable, but it requires a stabiliser and closer checks. In all cases, fresh fuel at restart clearly improves drivability and mechanical protection.
7) Fuel memo table
| Type of petrol | Recommended time without driving | Recommended action |
|---|---|---|
| SP95 / SP98 | 3–6 months | Tank ~95 % + stabiliser; dilution if > 6 months |
| SP95-E10 | ~3 months | Stabiliser essential; monitor humidity |
| SP98 + stabiliser | 9–12 months | Dry/temperate storage; fresh fill-up at restart |
Fuel FAQ
Can I drive with an old/new fuel mixture?
Yes, 50/50 dilution is common for reviving slightly degraded fuel. If the smell is very strong or the colour dark, prefer draining.
Is a stabiliser enough for 1 year of storage?
It helps a lot, but beyond 9–12 months it is safer to drain or to dilute very heavily with fresh fuel and replace the filter.