I have a 1985 Thunderbird, i Use to be able to fill it up ever week and a half. But after it sat for a couple of months I now have to fill up every three days. I am lost, I gave it a basic tune up.

Also every time I step on the breaks my oil light comes on, do you think it could be tied to that?

First off, attempting to measure fuel consumption by how often you fill up isn't a form of measurement. Get the actual MPG. In some states, there is a difference between "winter" and "summer" fuels. Don't let it warm up - start it and drive it immediately - it will warm up faster and won't waste fuel just sitting there. Most of the DIY manuals will show you how to retrieve your trouble code(s). But really, you can't measure performance or fuel consumption based on time - it's miles divided by gallons.

The oil light is probably just a bad sending unit. Ford Oil Pressure Senders are notorious for low reading, leaking and failure. If you're running the correct viscosity and grade of motor oil, change the sender and be done with it.

I drive it a lot less than I used to. I used todrive 80 miles a day now not even half that and still fill up more!

Until you do an actual MPG check - you'll never know if there's a problem or not.