Teak Oils - Are they safe on fiberglass?

I need to oil the teak runners on my boat. Can I do that with the runners in the aluminum tracks right on the boat or will the oil harm the fiberglass? I'm afraid if I take the wood strips out they will expand after adding the oil and not fit back in their tracks. Any thoughts?

I don't believe the teak oil will be harmful. I'd try to not get it all over the place as, at miminum, it makes a mess as any oil would on the fiberglass.

I'm not sure the teak will swell enough to make a difference either.

I'd be more concerned with the chemicals I use to clean and prep the teak. If you don't prep the teak in some fashion, either chemically, or by sanding, the teak oil does not absorb into the teak well, and does not last.

Is it possible to pull the slats out, prep the wood, put them back and apply the oil?

When I do my teak, I clean and prep the wood. I use a two part chemical which removes any grayed wood, mildew, dirt, etc. It is then thoroughly rinsed with water. Let dry a full 24 hours, or longer if required to be completely dry. If there are any rough spots, I do a lite sand with fine grit paper. I apply a heavy coat of teak oil and let dry 24 hours, or longer if required to be dry. I then apply at least 3 more light coats, every 24 hours. This method has provided a nice finish, and covering my boat, lasts at least two seasons. FWIW. BKH