Say I take a car in mint condition, leave it in whichever condition is best for long term sorage in an ideal temerature and climate. I also store a car battery, some petrol and some oil nearby in whatever would be considered the best possible storage. Assuming then no maintenance and no driving is performed at all would it be likely I could just fill 'er up, get in and drive 100 years later? 1000 years? 10000 years?
Not that long, most likely.
I mean, a car needs to have the parts on it moved around once in awhile, I think.
Unless it is, of course, in Battlefield Earth, where things start after 1000 years with no problem. 
I think it would be as long as a battery would hold a charge. I have no idea how long that would be.
Depends on just how good that “long term storage in an ideal temerature and climate” really is.
Mr Shine, how theoretical are we getting here? Can we store the car in a vacuum? If we can keep the metal components of the car from reacting with oxygen (and perhaps some other gasses), we should be able to store the car a ridiculously long time. Measured in millenia, perhaps?
Even 100 years under ideal conditions it almost certainly would not start. If you allow charging the battery before attempting to start, you still have the problem of many of the parts oxidizing (rubber, plastic, some of the metals, etc.) that would probably render it unstartable in 25 - 50 years, at most. Then you need replacement parts. If you are allowing replacement parts, then the best way to store it would be as complete plans and specifications. Then it will last as long as you can get records of that type to last. But that grossly violates the OP hypothetical. 
Since the OP is specifying external storage of the battery … I wonder (a) if, and (b) for how long a battery can be kept inert. Vacuum-pack it?
The gasoline/petrol is to be stored externally, as well … but gasoline evaporates, doesn’t it? And you can’t store it in a totally closed container because of the fumes, right?
It depends on the car.
I have a kit car which is basically a 1960 VW Beetle that has been converted to look like a 1929 Mercedes. While it doesn’t look like a Beetle, all of the mechanical parts (engine, steering, suspension, etc) are all original Beetle. For some reason, before I got the car, it sat in a garage in New Jersey for 20 years.
To get it technically “running”, all I had to do was change the oil, replace the battery, and put fresh gas in it. However, the brakes had seized up and the tires had a flat spot from sitting for so long. I put new tires on it and drove it around the neighborhood for a bit while constantly slamming on the brakes, and the brakes loosened up and worked fine.
The thing is, a 1960 Beetle is about as simple as you can get. VW had a philosophy with the Beetle that if it wasn’t 100 percent required to make the car go down the road, they didn’t put it on the car. Cars today most definitely do not follow this principle. You are going to have a lot more complex parts that can fail, a lot more rubber seals to dry out and fail, and all sorts of problems.
You would probably be lucky to get 10 years out of a modern car.
By the way, the battery can be stored for an extremely long time if you don’t use a sealed battery. Drain the electrolyte (battery acid) into a separate plastic container and then pour it back into the battery when you are ready to use it.
ETA: The gasoline is going to go bad even if you store it. I don’t know how well additives will work over decades. I would guess that a couple of years is the most you’ll get out of stored gas.
I suspect the tires would have rotted by that time as well, and other rubber-like parts would have dried/cracked/etc beyond usage making the vehicle difficult if not impossible to start/drive without replacement parts.
Vacuum cementing. Metal parts flow together over time, and it isn’t all that slow. NASA has to worry about that and take special precautions on anything that’s supposed to be in space for more than a few days. Unless the OP wants to hypothesize a specially designed car, as well as storage, vacuum won’t work.
… is that “flow” due to gravity, or more of a chemical melding? Or both?
What does NASA do about it?
Maybe can build the car out of the most chemically inert materials feasible, and then store it in an absolute zero vacuum
If you have a new, dry battery and store the sulfuric acid separately in an all glass container and store the car in a dry mine, like an old salt mine inside a container of argon.
You would want to store pure octane, not the mix they sell at the pump, in sealed stainless steel drums with no air space.
I believe it would last as long as the argon doesn’t dissipate.
I.E. the container containing it stays intact and any makeup bottles or system keep working and don’t run out of argon.
10,000 years if you can keep the argon supplied and contained that long.
Of course you would have to purge any air out of the upholstery foam in the car with argon and dismount the tires.
I’m kind of curious about this point, because I always hear anecdotes about “old gas” but haven’t really read any proper cites. Here are my anecdotes and conjectures:
I left a car (a 1988 fuel injected Honda Civic) stored for two years in an outdoor storage lot while I served in Germany. I left the gas tank full, depressurized the fuel system, disconnected the battery, put the tires in hatch back (the car on cinder blocks), and foolishly engaged the parking brake (had to do a brake job there under the sun!). When ready to start up, I don’t even remember if I had to jump it. The car ran perfectly fine on the old gasoline.
I often have old gasoline in my lawn tractor (4-cycle) and other 2-cycle lawn equipment. I don’t think it ever gets to two years, but again, everything runs just fine.
Gasoline as we use it is a distillate of crude oil, plus sometimes corn alcohol, plus whatever additives each supplier ads, including stabilizers. (I’m not sure what’s being stabilized.) The pure gasoline portion, of course, has been around for millions of years, although it was mixed with other petroleum ingredients, and sealed in rock. Does gasoline react naturally with anything in the atmosphere? What’s being stabilized? Plastic and metal tanks are porous to which part of the retail gasoline? PZEV tanks are supposedly non-porous, so if we use a California Focus, can we assume that retail gasoline in the tank will last forever?
I left a Mini for five years once. I recharged the battery overnight, flushed the carb, and it started first time. It too had flat bits on the bottom of the tires, but they smoothed out once they were warmed up.
I rescued a 1996 Peugeot 306 XN from under a tree where it had been sitting for 6 years, completely encased in vines and vegetation that we had to hack away. We hooked it up a running booster vehicle and fired it up and she started first time. There’s some French engineering for you!
I drove that thing for years, and nicknamed her The Green Leviathan since she was the biggest car among all my friends, and no matter how often I washed her the moss would grow back on the plastic bumpers (although the silver paint was just fine).
The only thing that failed was the centre shaft on the rear wiper blade, since the squirt nozzle was built onto the hub itself so the washer fluid was routed up through the centre of the shaft and it had obviously rusted at some internal joint, since running the rear washer pump resulted in the boot filling with liquid. The wiper arm itself worked fine though.
Here she is just a week or so before her untimely demise due to cam belt failure causing beyond-economic-repair damage to the engine.
http://img413.imageshack.us/img413/611/peugeot306.jpg
So, I would maybe cover the car with a tarp, put it in a garage, drain the coolant and washer fluids and include a few spares for things like the cam belt and air filter and so on.
My experience isn’t the same as yours.
My brother-in-law left an old pickup truck in front of his house for 2 years. I went down and put a new battery in it and after about half an hour of fiddling I was able to get it to run. It had about half a tank of gas and it ran like crap. I was able to drive it around the neighborhood a few times until I was able work the brakes free. then once I could both go and stop I took it to the nearest gas station. It had about half a tank of old gas and ran like crap. When I added half a tank of fresh gas it got a lot better. I drove the pickup to my house (about an hour’s drive), and by then the flat spots on the tires had mostly rounded themselves out. I drove the pickup around for a week or so and ran the tank almost completely empty. Once I filled it completely with new gas it ran fine.
I usually run my lawn mower in the spring on whatever gas was left over from the fall and have never had a problem with it. However, I’ve talked to a lot of people who have had problems with gas that was only 6 months old. I’ve been told that blended fuels decay a lot faster. I don’t know how true it is.
Here’s a good cite on the subject (I think we can trust this guy):
Reading through Cecil’s article, I get the impression that the fact that you left the tank full may have prevented a lot of oxidation and probably prevented water from condensing out of the air and mixing in with the gas too (no air in the tank, no water to condense out of it).
On the fuel issue, when I was in my internal combustion engineering class at the U we had a lab that was set up just after WWII, about 1947 or so, and much of the equipment was from that time.
In 1986, when I was there, we found several barrels of pure Octane and Heptane from 1946, so they were 40 years old at the time. they were sealed and burned fine in the lab engines, producing only slightly less horsepower than the fresh pump gas.
We figured it was from oxidation and speculated if the barrels had been better sealed and had no air at the top they would have been fine.
Also I have started a 1967 Chrysler Imperial after sitting for about 10 years and a 1975 Valiant after sitting for about 7 years, both had no particular fuel issues that I remember.
Of course it ran like crap – it was half a tank. Gasoline, stored properly, will not go bad in two years, but intimate contact with moisture and oxygen is the opposite of proper storage.
Electron migration from one surface to the other, so I suppose chemical melding would be the best descriptor. What they do about it is to make sure that the two surfaces are finished in compatible fashions, that the metals in contact are compatible, or coat them with something like teflon, or some combination of those things.
I think that would exceed the OP’s hypothetical by just a bit…
I used to have a Honda CX500 motorcycle; it would never start in the spring without some serious effort. (Plus, half the time, if I didn’t take the battery out and keep charging it occasionally, it would destroy the battery. Freezing a battery is not pretty.)
Eventually, someone with real mechanical ability pointed out that I needed to drain the carb bowls. There’s even a screw valve to do this; otherwise, in the spring the gas smells like turpentine, the carb floats stick due to the crud from old gas, and stuck in the up position they don’t allow fresh gas in the bowl so the engine gets no gas. Handy hint #23, lightly tap the bowls with a hammer to shake the float loose.
Once driven for a tank or so, it rode fine that season…