Some of the people are money savvy and I am one of among them. So I always prefer lpg on petrol and diesel. It depend upon your expense bearing capacity and requirement of car also matter in this. If you run the petrol compatible car mostly on lpg this thing effect the engine of car. So you need to take care of everything.

I do less than 13000 miles each year but I've just switched from a petrol to a diesel. The petrol was a lovely Vectra sri that cost £300 and it was great to drive. The diesel is a Vectra estate that cost £450. I reckon that I'll "save" the difference in around 2000 or 3000 miles and it'll "pay for itself" after about 6000 - 8000 miles.

I've not sold the sri yet and I'm going to miss putting my foot down and zipping along but common sense says it needed changing. I reckon I'll try and get a lpg or, at the very least, a bigger-engined diesel next. For now I'm settling for chugging along in the diesel.

Don't know whether this is still relevant, but the tipping point used to be this. 13000 or more miles a diesal works out cheapr and less than 13000, an economical petrol works out cheaper.

When buying a car, it is important to take a lot of factors into account. Although diesels tend to be more economical than equivalent petrols, they are normally more expensive to buy and therefore it is worth looking at how many miles you do as it could be cheaper to buy petrol. Also diesels tend to be more expensive to service. However if you do a lot of miles every year, diesels are normally the cheaper option. Doing your sums thoroughly before buying a car could save you a lot of money and you may get a few surprises. Don't let the salesman talk you into buying something that isn't appropriate for your needs.