Parking in Madrid

Bringing the car to madrid is a very good idea if you can, cause there are many interesting places and towns to visit in the outskirts, and a car will just make your trips easyer and make you save a lot of time. For the city centre however, I wouldn't recomend you to take the car.
Traffic is a bit hectic, specially at rush hour, and parking ain't easy at all, because most parking spots are coloured in green and blue meaning you have to pay (one is more expensive than the other but I cant rememeber wich one). You can, however, find a free parking spot if you drive arround for a bit, although it may not be too close to where you live.
I suggest you take the car, patiently look for a free parking spot, and leave the car there till you want to visit the outside of Madrid. For the centre, public transport, specially Metro but also buses, works veeeery well, and is really cheap (1.5€ for a single ticket, and you can buy "abonos" for 10 or 20 trips, or even get a monthly unlimited "abono" if you're planning to move a lot. It's quite cheap too)so I recomend you use it.
You can also use the car at nigh if you go out cause metro is closed from 1.30 to 6 am. Night buses also are an option but they aren't so good as during the day so personally I prefer teh car for night life, cause it's also much easyer to park than during the day. But don't drink and drive! Police controls are pretty frecuent.

ask if you need more info

forgot to say the colour system for payment parking doesent work at night or on sundays. Avoid also yellow areas, it's not alowwed to park there at any time, and always look for traffic signs forbidding you to park. If you see a free spot it may be cause it's not alowwed to park there. I've ahd my car towed a few times for this common mistake

Excellent, thanks very much. I have booked the ferry now so it looks like the car is coming one way or the other.
I have heard that parking outside the M30 is free. Is this true and if so how far is this from the city center?

Thanks

Not really, you can also find green/blue areas aout of the M-30 circle. I live 40 km in the north of Madrid and we have coloured areas there too haha damm crisis...
The difference may just be that the concentration of coloured areas is lower but you can find free parking in the centre too. As I said it takes patience and accepting you might have to park at a certain distance.
However the distance from the M30 to the centre is very litte. Certainly not a walking distance but no more than 10 minutes on a metro. Anyway, there's really no point. Id try to park in the centre. Even ask people from the area if they know a free parking street (generally a hole street is either free or coloured)

Hi, I can recommend you the following safe places where to leave your car for weeks and nearby a metro station. These are a bit far from the centre but I know these neighbourhoods are damn good.

The first one is Las Tablas, the second one is Montecarmelo and the third one is la Gavia. There are a metro station just next to it and it is possible to park very easily.

Of course, as you said earlier there are some other areas of the city where it is not necessary to pay, but I recommend you to do a little research about that neighbourhood before leaving your car for extended periods of time.