2000 Buick maintenance problems. Why is such an unused car in bad shape?

Ok first of all that is not impossible, just do the math. Let's say he bought it new so he's had it for 12 years, 31000 divided by 12 is about 2500, so every year he only went 2500 miles. So now we divide 2500 by 12 again to figure out how far each month which is about 200. So every 3 months he would've went around 600 miles which means he would've been about a quart low on oil and that is far from being able to cause any problems.

Now for your questions, a car can consume oil for various reasons, it can just leak out or burn it and that can be due to valve seals, pcv valve, etc. That and the running badly issue are most likely related, we don't have enough info to really diagnose it for you tho sorry.

All GM vehicles since 1995 have a long life coolant (Dexcool) that is advertised to be good for 150,000 miles IF the plastic coolant recovery tank is always kept 1/2 full. Personally we drain, flush and CLEAN any cooling system after five years of use.

We would suspect since the car was never driven vary far or at fast highway speeds the the inside of the engine *could be filled with moisture sludge, varnish and carbon. Peak down through the oil fill cap with a flash-light. If it's black inside you are more than likely correct. The oil either wasn't changed as often as people thought or the wrong oil was used for his type of driving.

Mobil1 5W-30 will gradually clean the inside of the motor out. The throttle body should be removed from the intake manifold and cleaned. A Chevrolet dealer could professionally clean the fuel injector nozzles. The motor gas iridium spark plugs that don't need changing till 100,000 miles. The ignition wires should be changed every five years or 50,000 miles. Age causes electrical resistance in all ignition wires.

The automatic transmission fluid should be changed along with the filter every five years regardless of mileage.

*The brake fluid should be changed every five years because moisture enters the vent hole cover in the master-cylinder reservoir. Water mixed with brake fluid will cause the wheel cylinders and brake calipers to seize sooner or later. Water will cause the brake fluid to boil at a lower temperature than new fluid will. Water in the brake fluid will also cause the brake lines to rust from the inside out.

We have an old Winter beater 1999 grand Prix with the very same engine. It's well taken care of and gets 33 mpg. on trips when it's hot in the Summer. 29 on trips in the Winter.

*Don't let Paul, the non-mechanic ruin your day. He's putting the horse in front of the cart! Have a trusted mechanic do an inexpensive *cooling system pressure test to see if you have any external or internal coolant leaks.

not driving a car as often as it should be driven is worse than putting a lot of miles on it. allowing it to sit lets it rust up inside the engine and the seals and rings dont seat properly which explains your oil loss. you might have to change gaskets and seals then drive it regulalry to work out the kinks. i bought a 95 t-bird with only 60,000 miles on it and a month or so had to change the intake gaskets because water got in the oil. so the best thing to do is tune it up if you havent already, find out where the oil is going - is it burning or leaking somewhere?- fix that problem, and then DRIVE IT. cars are made to be driven. if not they will go to pieces. good luck

"Doesn't sound good"--{Oil} Blown Head Gasket(s) and/or Bad leak at Valve Cover Gasket(s), Major Tune-up Needed, "Good Radiator Shop" to Flush & Check Cooling System. {Lack of Complete Maintenance}.