I get a warning for low brake fluid when I brake really suddenly (didn't use to happen). I'm assuming I just need to top it off...

what should I top it off with?

dot 3 brake fluid

You should never have to top off your fluid. Your brakes are probably worn, such that the pistons are over-extended, causing the low-fluid warning.

You prob just need to replace your brakes... If your fluid is really "just low", then you have a leak somewhere. However, a leak in the system usually causes the pedal to go to the floor.

Yes, but...the G35 pistons seem to suck down an inordinate amount of fluid as the pads wear. You will very likely encounter a low-fluid light even when the pads have 30% life remaining. So look at the warning light as an early indicator of brake pad replacement. Top off the fluid and start making arrangements for new pads in the next few thousand miles.

Really? When my low-fluid indicator came on, my front pads were worn almost all the way to the brackets. Luckily I had already ordered pads (they were backordered at the time), but I didn't realise my pads were that low.

Just for safety sake, I'd take a look at the brakes, before topping off the fluid.

Of course, inspecting brakes is always a good thing to do. But how far were they worn with respect to the wear indicator prongs? When those guys start screeching, you need to do something fairly soon.

theres an OCCASIONAL squeak, but it's pretty infrequent... about a month ago i had my pads looked at, and they said i had a few thousand more miles. i do drive about 400 miles a week, though--

should i top off the fluid and change the pads sometime in the next few weeks?