Well sorry to hurt your feeling but that is a stupid question.
There is no thing as monthly maintenance.
Its not a horse you are talking about that you have to feed it everyday no matter what and vet appointment and keeping its place clean etc.
Its a freakin car. You can get it washed everyday if you want to, or dont pay any attention at all. And fuels and oils depend on your usage. More use mean more fuel and oil. Less use mean less $$$ to spend.
And since you were not nice to me in your reply, i will say this, "get all this through to your thick skull."
cheerio.
