When I bought my Pajero I would have preferred the diesel engine. At the time diesel fuel was around the same price as unleaded and since the diesel engine uses about 6 litres less fuel every 100km it had significantly less running costs. Unfortunately the additional $9000 odd price tag pushed the budget just a little too far and I opted for the 3.8 litre v6 petrol engine. In hindsight the petrol was actually the best choice anyway as the price of diesel has risen so much in comparison to unleaded that the savings in consumption have been reduced significantly. The fact that the petrol engine can also be converted to run LPG makes it actually cheaper to run than the diesel and the conversion is only around $2500. The petrol engine is also much smoother and quieter. The diesel may still have an advantage for towing and heavier 4wdriving where more torque is desirable but the Petrol/LPG dual fuel system suits my use of the vehicle.
LPG conversion cost
The conversion to LPG was painless except that at the time the federal government had just introduced a large rebate scheme to encourage drivers to convert. Because of this, availability for LPG tanks was difficult and I had to wait a few months to get the work done. On the good side the $2000 rebate reduced the cost of the system from $4500 to $2500 which made it worth the delay, my timing couldn't have been better. The Impco brand LPG system that I chose was a fully injected system that gave the best performance, safety and economy. There were cheaper LPG systems for around $2500 however these were simpler systems that are not fully injected. I had heard of problems with these like backfiring, engine damage and lower fuel economy.
LPG installation
The installation was done by Carb&Gas at Wooloongabba in Brisbane. I was completely amazed at how neat the job was. The fuel intake cap fits next to the unleaded intake inside the fuel door. The LPG tank fits under the rear floor by removing the third row rear seats. The bottom of that cavity was cut out and lowered to increase the space slightly. The LPG fuel guage is a small panel with 5 indicator lights and an on/off switch that is mounted in the centre consol in front of the gear lever. From the outside there is no sign of the installation apart from the little LPG sticker added to the registration plate.
LPG performance
So how does it perform? Great! The car starts on unleaded and runs until it warms up before switching over to LPG. There is a small "pssst" noise, the indicator light on the LPG panel changes colour and then you are running on LPG. There is no noticable difference in power and if anything the engine appears to run a little smoother. On long hill climbs the engine is definately less "pingy" which is noticable when running on lower octane fuels. In effect LPG feels like running a premium type unleaded fuel. If you listen to the engine up close it makes a slight "tappy" noise when running on LPG and that's about the only noticable difference.
LPG economy
The LPG tank's effective capacity is about 68 litres as it cannot be filled to 100% as part of its safety design. That 68 litres will do between 350 and 400km depending on driving conditions. That's between 19.4 litres per 100km and 17 lph, an average of 18.2 lph. On unleaded the car was averaging around 15 lph which means that LPG uses about 20% more LPG than unleaded. The big win is that LPG is usually less than half the price and sometimes even a third the price of unleaded which equates to a huge saving! I kept a log book of fuel usage and calculated that I hade saved $2500 in 18 months which meant the system had paid for itself. Now all those savings go straight to me! Another great advantage I have gained is that with the standard 90 litre unleaded fuel tank covering about 600km I now have a range of around 1000km before needing to fill up.
I am aware that the government is going to increase the tax on LPG over coming years but even with the extra few cents that will be added it will still be a huge saving and worth doing.