Technically no. Around the 1980's the way car/motorcycle warranties work changed. If you are pulling a warranty claim NOW and the cause of the original problem can be traced to something the end-user did then the warranty is void for that repair. So If the timing chain breaks and the dealer says, "Oh, you changed the oil yourself the warranty is void!" then THAT is a lie.
Now if you removed the air-filter and engine detonated to the point where there was a catastrophic engine failure then that would not be covered...
So as long as you properly change the oil (It's not that hard) you have no worries. Most big dealerships will say things like that to sucker you into paying them a LOT of money for them to do work for you. When I bought my bike they tried selling me on everything and laid out how 'expensive' various repairs were and how I needed their service plan. When I brought up that they were flat out lying to me as the "$1,000 it normally costs to fix a fuel pump" didn't apply to my carbureted bike and $1,000 to fix a fuel pump was a bullshit number in itself I magically stopped getting jerked around. :evil6: