I noticed today that the plastic gas door hinge is cracking in two places on the main "spine" of the hinge, the part that takes the brunt of the opening force. Each part is cracked about 3/4", so I have to be very delicate opening the gas door. Shutting it is ok though since it pushes the cracks back closed.

I absolutely do not want to have to get a new gas door and have it paint matched/blended/installed. Too much paint matching risk.

I tried to use some Gorilla Glue super glue on it today, but it didn't hold very well; then again it was 90 and very humid. I will try again next time I am by the car.

Should that fail, what else can I try to preserve the door I have?

 

I think this would be the best option, new or used door, and paint. Imo waterborne seems to match slightly better than solvent based, assuming a BC/CC system. You might have less color match headaches with a shop using a waterborne system.

You could drill a hole on the edge of the cracks to stop it from running further and repair with 3M plastic repair (tab). However, the repair will look like someone drilled holes and applied plastic repair.

 

I'm going to try another very fine, clean application of Gorilla Glue and see if that holds here in cooler weather, otherwise I was looking into Plast-aid as a possible solution.

If it wasn't a part that required painting, I would just get a new one and be done with it but I want to see if I can preserve the one I have since I think it is fixable, at least until I repaint the car in the future...I only open it several times a year to put gas in.

 

If it is made out of ABS you could use plastifix. It won't work on polypropylene plastics though.
http://www.urethanesupply.com/PlastiFix/

I have used it with good results on ABS.

 

Have you tried a good 2 part epoxy