Synthetics can go longer than 3 or 5,000. But if you go for conventional it really isn't much good after 5,000.

Most fuel treatments state that you should use them with each fill up. And since a lot of reviews I've read say that they don't do much good, that kind of makes sense I guess...

It's cool you love your car, and I hope you like it here. Welcome and watch out for leg humpers.