Ford Falcon Engine Problems

It's not normal. Make sure you are using the recommended antifreeze in the coolant; that stops electrolysis, which is probably what's causing your problem.

The problem was solved when the external oil cooler was introduced. It was no longer in contact with the engine coolant, so there was no chance of coolant getting into the auto and causing the damage that was common when the cooler was in the radiator.

Based on your figures it's consuming about 50 percent more LPG than it should. It should be doing around 17-18 L/100 km on LPG, not 24-25. I would have the LPG system serviced, and the spark plugs and plug leads changed.

Ford's claimed fuel consumption for that model was 11.4 L/100 km overall, which means you should get 550 km or so from a tank of fuel. Regular unleaded was Ford's recommended fuel for your car, that's 91-  octane. They also gave the tick of approval for E10.

It is quite a common problem with cars that have to start on LPG. Most dual-fuel cars get around it by starting on petrol and then automatically switching to LPG after a few seconds. There's probably nothing wrong with your car; if it's running well otherwise, I wouldn't be concerned about it.

A recalibration using a chip would probably help, but I don't believe there is one available for your car. I would be giving it a tune-up, service the LPG system, and replace the spark plugs and leads, to make sure the car is running at its best.

The BA is well out of warranty, so the issue of being fixed under warranty doesn't come up, and it's doubtful that Ford would have automatically changed the head on the basis of a maybe. The best thing to do now is to repair the head.

It is good practice to run approximately 20 litres of petrol per month to keep the petrol volatile. The reason it's recommended you maintain a quarter of a tank of petrol is to protect the fuel system components such as the petrol pump, which may remain active during operation on LPG.

The fuel consumption is maybe a little too high, I reckon 11-12 L/  100 km would be closer to what you should get, but a lot depends on the load you carrying, the speeds you drive at, the traffic density etc, which makes it hard to be too specific. As for the engine I reckon you need to have it thoroughly checked over, it doesn't sound healthy to me.