I've had a hood blackout on my Land Rover Discovery for a while, well, two actually. Needed to replace the first one. I usually used Turtle Wax Ice clear liquid wax on it and all the black plasticky bits. It lasts a decent amount of time. Just make sure you put this stuff on before you wax the rest of the car otherwise the paste wax will muck up all the plastic and the hood decal just won't look right.
Keep in mind this decal is a 3M or some similar manufacturers product, or at least I assume so. Typically, these things are designed to last 5-7 years at the most before they need to be replaced. That's why I mentioned I've replaced one previously. Even with all the good love you give to these with any product, (my luck with 303 was not very good, and I've stopped using it on the boats I manage), the decal starts to dry out and crack.
Removal at this point is a bit of a pain then a lot of elbow grease with Xylene and all the adhesive residue will be gone and ready for a replacement.
Back to the original question though, anything you do it will keep it looking good, otherwise it just starts to look dark and bland. The Turtle Wax stuff I used just kept it looking deep black without losing the matte finish.