You filled up at a pump you do not normally use, and within a few kilometres the car starts acting up. Jerking, mild power loss, maybe an unusual smell. The problem is not the gas system itself but what you put into it. LPG quality at pumps in BiH varies more than most drivers realise, and bad fuel causes cumulative damage if you do not catch the signs early.
What Bad LPG Actually Is
The LPG that cars run on is a blend of propane and butane. The ratio is not arbitrary: in winter, a higher propane share is needed because butane barely evaporates at low temperatures, while in summer the mix can contain more butane since ambient warmth helps it vaporise. When the ratio does not match the season, the engine gets fuel that evaporates poorly or burns at the wrong conditions.
Beyond the wrong propane-to-butane ratio, bad LPG can contain contaminants: heavy residues from refining, moisture, and mechanical particles. These do not burn. Instead, they collect in the filters, the reducer, and on the injectors. Moisture is especially problematic in winter because it can freeze in the valves and block gas flow on a cold morning start.
It is worth understanding that "bad LPG" does not necessarily mean the station is deliberately selling inferior product. Poor fuel quality comes from the supply chain, storage, and transport. The end user has no way to test the gas at the pump. All you can do is learn the signs and react.
How Bad LPG Shows Up in the Car
The clearest signal is a change in engine behaviour right after filling up at a new pump. If the car was running fine, you filled up, and now it jerks or loses power, the timing points squarely at fuel quality. That is a completely different situation from the gradual decline caused by worn filters or spark plugs.
The second sign is filters clogging faster than usual. If you replace your LPG filters regularly every 10,000-15,000 km and notice they are getting blocked well ahead of schedule, that usually means the gas from your pump carries more contaminants. The liquid-phase filter will show visible sludge rather than just mild discolouration.
Deposits in the reducer are a third indicator. The reducer converts liquid LPG into gas, and contaminants that get past the liquid-phase filter settle on the membrane and inside the chambers. This gradually changes outlet pressure, so the engine runs poorly on gas until it warms up, loses power under load, or spontaneously switches back to petrol. More detail on how the reducer affects performance is in the LPG service advice.
A noticeable gas smell in the engine bay or cabin after filling up also deserves attention. Low-quality LPG sometimes has a stronger odour because of impurities that cleaner gas does not carry in the same concentration.
How to Protect Yourself from Bad Fuel
Complete protection is impossible because there is no way to test the chemical composition at the pump, but a few habits significantly reduce the risk.
Fill up at high-volume stations. A pump that moves large quantities of LPG has faster stock rotation, meaning the gas spends less time in the tank, absorbs less moisture, and degrades less. Small stations with infrequent deliveries carry a higher risk of old or poorly stored fuel.
Stick to one or two pumps. When you always fill up at the same place, you have a baseline. You know how the car runs on that gas, and any change in behaviour stands out. If you constantly switch pumps, it is harder to link a symptom to the fuel because you have no reference point.
Do not always chase the lowest price. The price difference between pumps is usually a small amount per litre, but the quality difference can mean significantly faster filter clogging and shorter component life. Paying slightly more per litre is cheaper than replacing filters twice as often.
What to Do if You Filled Up with Suspect Fuel
If the car starts running poorly right after filling up at an unfamiliar pump, the simplest step is to switch to petrol and drive on petrol for the next stretch. This does not fully solve the problem, since the bad gas is still in the tank, but it reduces the load on the gas system while you use up that fuel or replace the filters.
Replace the LPG filters ahead of schedule, without waiting for the regular interval. A clogged filter from bad fuel is not worth tolerating: replacement is quick and inexpensive compared to possible damage to injectors or the reducer. A regular LPG system service includes filter replacement and a full component check, so that is a good time to inspect everything.
If a pump has proven to be bad, simply avoid it going forward. There is no point making a fuss, but there is also no point repeating the same mistake.
Winter, Summer, and the LPG Mix in BiH
In BiH, the LPG blend is not controlled as rigorously as it should be. In winter, the fuel should have a higher propane share (typically 60-70% propane versus 30-40% butane) because butane barely evaporates below zero. If a pump sells a summer blend in January, the engine will struggle to start on gas, run rough until it warms up, and fuel consumption will be noticeably higher.
In summer, the issue is reversed but less pronounced. Excess propane in summer does not cause major drivability problems, though it can slightly increase consumption. The issue is mainly economic: propane is more expensive than butane, so gas with too much propane in summer means you are paying more than necessary for the same energy content.
Drivers have no control over this because the propane-to-butane ratio is not displayed at the pump. The only indicator is engine behaviour: if the car starts poorly on gas in cold weather but starts fine on petrol, the blend may be wrong for the season.
How to Tell Bad Fuel Apart from a System Fault
This is the key question because the symptoms of bad fuel and a faulty gas system can look identical. The difference is in the pattern.
Bad fuel produces symptoms that are time-linked to filling up. You filled at a new pump and problems appeared immediately or within a day or two. You replaced filters, went back to your usual pump, and everything returned to normal. That pattern clearly points to the fuel.
A system fault produces symptoms that do not depend on the pump. If the car runs poorly on gas regardless of where you fill up, if the problem persists after filter replacement, if it worsens gradually over weeks, that points to a mechanical or electronic issue in the gas system itself. In that case, read the rough-running-on-gas advice, which covers component-by-component diagnostics in detail.
If you are not sure whether it is the fuel or the system, book an appointment and we will go through the entire gas system. Diagnostics show the condition of every component and quickly clarify where the problem is coming from.