Should I have my 2000 Mitsubishi Shogun converted to LPG to reduce fuel consumption?

I'm being offered a 2000 model Mitsubishi Shogun GLS V6 LWB 3-litre petrol model free of charge by a family member. It's a very nice car inside, and has only done 30,000 miles, but it drinks an incredible amount of fuel. I was wondering if you would recommend having it converted to LPG? I'm guessing we would probably do up to 10,000 miles a year in it. If not, have you got any other ideas how I could cut down on fuel consumption?

One other quick question. As far as I'm aware, it has never had its cambelt replaced. Would you recommend that I have this replaced?

Asked on 5 February 2011 by BS, Hendon, London

Answered by Honest John
Yes, needs its timing belt replaced.

A decent LPG conversion will cost £1,500 - £2,000 and the cost of LPG is rising faster than other fuels because the world price of LPG is rising faster than other fuels (the price of fuel is made of fuel + fixed road fuel tax + VAT, so the fuel price and the VAT rise, but the road fuel tax stays the same). If the engine has variable valve timing then on LPG it might eventually burn out its exhaust valves. That said, every Toyota Corolla Altis taxi in Bangkok has a VVT engine and runs on LPG or CNG. A lot of Thai HGVs and minibuses now also run on CNG, but the tanks are huge. More here: www.honestjohn.co.uk/faq/lpg-and-cng

It doesn’t seem to restrict performance. Together with 16 other people I was driven at well over 100mph for about 10 miles in a CNG-fuelled Toyota Commuter. We even passed a Porsche.
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