they wont give a hoot.
Its very unlikely to affect insurance however you should still tell them
Im sure you would if they decided not to pay out on a claim you make...
One important thing to remember is that you are legally obliged to inform insurers of any modifications that you do. This is vitally important as failing to declare them can potentially invalidate your entire insurance policy. This would mean in the event of you making a claim, and the insurers discovering an undisclosed modification to your car, you could be left high and dry with a null and void policy. The modification disclosure rule is normally found in the terms and conditions of a policy, with the onus very much on the policyholder having to inform the insurer, and not the other way round like many seem to believe.
But none of that is any sort of modification. If you feel it is, then you should inform the insurer if you change from, say, Castrol oil to Millers Oil, or from Dunlop to Falken tyres, or fit a non-genuine front wing There is no need to inform the insurers of routine maintenance and repairs and your engine can be any colour you like. I always paint my engines original BMC green unless asked to do otherwise. You don't seriously think an insurer is going to try to void a claim on the basis of wrong colour engine block do you.
If i beleve that a modification i make will effect an insurance pay out of course i will tell my insurers. The point im trying to make is all modifications from standard should be declaired to your insurers. Most small items wont even put the price up so its silly not too tell them.
Would you rarther spend 5 minutes on the phone declairing all mod's most likely not affecting the cost OR find out after you crash your car that they wont pay out due to modifications.
If you change the make of oil, tyre or wing and its of the same specification as the standard item there wouldnt be a problem However if you fit fibreglass wings and avon moulded slicks (road legal) then i beleve your insurance company should be informed. Where do you draw the line? Tyre valves? window tint? high performance engine?
These days you never know what is going to happen. When i crashed my moped a few years ago my insurer wouldnt pay out as i had fitted different wheels and tyres. They beleved i wouldnt of crashed if the standard items were fitted.