No GREASE IS NOT GREASE regardless of temp rating. There are "types" beyond temp ratings. Greases containing silicone should never be used where that migration of silicone can cause issues. In the case of the valves (or other items like them) silicone will migrate badly. It will get into and clog fine orifices (i,e, the valve body spools) and or the main orifices that regulate full fuel flow. I'm trying to help you here. Another thing (though doesn't apply to grills) is silicone is insidious in how it infiltrates and migrates everywhere it doesn't belong. Even something as innocuous as Armor All (and other silicone treatments for shining things) should be avoided in the engine compartment. As it will infiltrate the intake system and ruin MAF sensors, O2 sensors and many other ones. Yes, it IS that bad. It should ONLY be used where it is designed to be used. It is excellent at isolating and insulating electrical connections against salt and moisture (hence use of dielectric grease) it is excellent in some formulations when exposed to water to lubricate rubber hence it's use by plumbers to grease O-Rings in WATER valves, ir lubing a gasket on a sewage connection (also water I guess). Used correctly silicone formulated greases can be VERY effective at lubing a window track for your car though again because of it's migratory nature it can permanently render the glass unable to be effectively cleaned no matter what you use on it. Believe it or not silicone spray is even used in commercial baking as a release agent as it's fairly inert (in pure form) in the human body. But, again it should not be used where it does not belong. Now that being said take my advice or leave it. It's up to you if you want to ignore experience. Me? I was taught long ago we have twice as many inputs as outputs for a reason.

Good luck whatever you do