Holden Calais Problems

The Holden is more refined so, although both cars get The Tick, I'd go for the Calais.

The guiding range if it were sold privately would be $14,000-$16,000.If it were traded in it would be valued at $11,000-$13,000. On average a 2009 Calais would be expected to have done 80,000-130,000 km. The car you are considering has done considerably more kays than the average 2009 model, but at $10,000 it’s priced well under the market value. You should check for oil consumption, there have been reports of the 6.0-litre V8 using oil. Apart from that it comes to condition.

I'm not aware that Holden has said there is a fault with the engine that causes the high oil consumption; the reaction from dealers is usually the one you got, i.e., to monitor it. Ask the dealer to monitor it themselves and if their results show high oil consumption it's much easier for you to request remedial action. I don't believe there is any difference with the VF.

It could well be a valve lifter that's draining while the car is standing and the engine not running. It might be a case of establishing which lifter is at fault and replacing it, but you need an experienced mechanic to listen to it to determine where it is coming from. If it only happens when the engine is started from cold it might be necessary to leave the car with the dealer overnight.

An experienced mechanic should b able to pick the difference between tyre noise and a bearing rumble. I would have an independent mechanic drive the car and tell you what the noise it. That way you should be able to get it properly resolved.

The main things to be aware of are the start-up knock in the engine that plagued the Gen III, also the rear suspension clunk due to warn bushes, and the rear tyre wear.
 

They do have problems; you are not alone. But you shouldn't be left with the problems, as you have reported the issues and they are being dealt with. I would keep the pressure up on the dealer and Holden to ensure they don't drop the ball.

The oil is probably coming from the rear main oil seal on the crankshaft. It's relatively common and shouldn't be of great concern providing it's not a large pool of oil. Check the engine oil level regularly and if you see it dropping rather quickly have a mechanic check the leak. There are anti-rattle washers in the brakes and they are sometimes lost or not replaced when the brakes are serviced, so have a brake specialist check them for you.

The backfire you are hearing is the gas igniting in the intake manifold, which is quite common with cars running on LPG. A random spark usually causes it, and the plug leads usually cause that. It's not the LPG. I'd take it back to the installer and get his help.