If I have a T12 fluorescent light fixture, can I use T8 tubes in it? T8 and T12 tubes both utilize the G12 pin configuration on their ends, so physically, a T8 tube will fit a T-12 fixture - but will the innards of the T8 tube be electrically compatible with the ballast that is supplied with a T12 fixture?
I think a T8 would draw less current than a T12, and so would work. I doubt is it doesn’t work you would be out much more than a short lived T8. I wouldn’t leave it on and unattended at least for a while.
It depends. Lok at the ballast. Some are rated for T-12 or T-8. Some can work with T-8 bulbs a long time some will not last long.