LPG tends to pull down a vehicle’s performance by a small percentage, but not enough really to notice the difference under normal driving conditions. You may tell of this is if you are driving the fast, under heavy load or requiring high performance. Very few people should drive under those conditions, so the clipping of performance will not even be noticed. Typically, people who convert from petrol to LPG are ones with vehicles with larger engines, and more so to help curve fuel cost. A larger engine will be even less noticeable with the performance end because they already out perform smaller engines.
LPG is a cooler burning fuel, therefore the engine does not produce as much heat or pressure to the cylinder. Because it is cooler burning it has less “power” per combustion charge. Because of this the reaction of the vehicle (the foot on pedal) will probably press down more, trying to get more “umph” out of the fuel, but in doing so will use more fuel. The key is to have patience and allow acceleration to happen naturally without over gassing the vehicle. If you do not do this, the result will mean more stops for fueling, around fifteen percent more stops to fuel.
The biggest plus to converting to LPG, even if you have to purchase 15% more, is that it has been typically about half the cost of petrol, and more than half that of diesel.
The issue with LPG in the engine is the temperature LPG turns to a gas vapour is the normal atmospheric temperature. Because of this, because the engine providers a hotter environment, when LPG converts into gas vapour, it evaporates faster, and because of this, in spite of the cooler burning process, when the evaporation occurs, the heat jumps up in the cylinder head. This may cause concern for the need to monitor the cylinder head temperature. However, not all vehicles have a temperature device on for the cylinder head temperature.
An LPG engine will heat up faster due to the cylinder head temperature, even with a cold engine. Petrol engines take a while to warm up, so this is a good thing for engines. LPG is high octane and runs cleaner through the engine. You will not experience sputters or knocks using this fuel, as it is clean burning. Ironically, though rapid vaporization causes excessive heat on the cylinder head, it causes excessive condensation and icing on the regulator. This is another reason not to put the vehicle through rapid acceleration, which causes these conditions.