One of the first questions we hear after an LPG installation is: "Why does it use more than gasoline?" It does, that is a fact. But how much more is what makes the difference between normal operation and a problem that is costing you money.
How Much More LPG Normally Uses
LPG has a lower energy value per liter than gasoline. That means the engine needs more liters of LPG to produce the same power. In practice, the normal difference is 15 to 20 percent higher consumption in liters compared to gasoline.
A concrete example: if your car uses 8 liters of gasoline per 100 km, on LPG it should use somewhere between 9.2 and 9.6 liters. Since LPG is roughly half the price, you still save 40 to 45 percent on fuel.
If your car on LPG is burning 10, 11, or more liters under the same conditions, something is not right.
When Consumption Points to a Problem
Over 25 percent difference compared to gasoline is a signal to have the system checked. Here are the most common causes:
Bad Map Calibration
The most common reason for increased consumption. The LPG computer controls how much gas it injects based on electronic maps. If those maps are set to inject too much (rich mixture), the engine runs fine but wastes fuel.
This happens for two reasons: either the system was not calibrated properly in the first place, or the parameters have drifted because nobody did a recalibration during service.
Dirty Injectors
LPG injectors that are dirty or worn do not close fully or open imprecisely. The result: instead of a precise dose of gas, the engine gets more than it needs. On one injector the difference is small, but multiply that by four cylinders and consumption climbs noticeably.
Reducer Problem
The reducer converts liquid LPG into gas and regulates pressure. If the membrane inside the reducer is not sealing properly or the valve is worn, gas pressure becomes unstable. The engine gets sometimes more, sometimes less fuel, and the computer tries to compensate by injecting extra.
Leak in the System
An LPG leak does not have to be large to affect consumption. Even a small leak at a fitting or hose means part of the gas escapes into the surroundings instead of reaching the engine. Beyond consumption, this is also a safety concern that needs immediate attention.
The Problem Is Not the LPG, It Is the Engine
This is a situation we see often. Someone comes in saying "the LPG is burning too much," and when we check, gasoline consumption is higher than it should be too. Worn spark plugs, dirty gasoline injectors, vacuum leaks, or a faulty oxygen sensor. All of these raise consumption on both fuels, but it shows up more on LPG.
How to Check It Yourself
Fill the LPG tank completely, reset the trip meter, and drive normally until you empty the tank. Divide the liters used by the kilometers driven and multiply by 100. Compare that to your gasoline consumption under the same conditions (city, highway). If the difference is over 25 percent, it is time for diagnostics.
What We Do When Someone Comes In With This Problem
We connect diagnostics to the LPG computer and check the parameters in real time. Within 15 to 20 minutes, we can see whether the problem is in the maps, injectors, reducer, or somewhere else. Often a recalibration and cleaning is all it takes to bring consumption back to normal.
If you have noticed your LPG consumption climbing, do not ignore it. Every extra liter is wasted money that you were trying to save by installing LPG in the first place. Give us a call and we will take a look.