I always have my car serviced once a year. Keeps it running better and cheaper in the long run to keep it maintained.

I didnt think about the effect it would have on the environment really but its nice to see that it is more green.

Some vehicles need a service every 6,000 miles , my VW has an oil change and new oil filter every 6,000 miles ...servicing needs doing more frequently than once a year !!! also some people will maybe only do a few thousand miles a year and others many many more than that. It is important to check your cars handbook for details on service intervals. Good maintenance saves you a fortune as does getting clued up re your vehicle and its habits shall we say. A Haynes manual is a great idea even if as I do you in the main only use it for diagnostic purposes.

Homeopathy, cheap. effective and with a miniscule carbon footprint.
A VW Polo is for life not just for learning in

Changing the oil is a good idea and keeping the tires in good shape will help a tiny bit on gas. The time to change the oil is different for every car. Anytime i can save on energy usage/bills i give it a go like swapping all the lights in my house to CFLs it wasnt cheap but im seeing a savings every time a get a bill from the electric company and i've had double glazing put on my windows so that my AC is running less now to cool it in the summer.