I trust my oiler on my Mercury 115. Alarm test at every key start confirms buzzer.
Not to hijack, but I add a small amount of TCW3 2 Stroke Oil directly to my fuel to help with lube and conditioning of the fuel tank and system in addition to reducing the harm of ethanol in the gas. I also do that for my motorcycle and lawn equipment, all at 1 ounce of TCW3 oil to every 5 gallons of gas, somewhere around a 640 to 1 mix. Been doing this for a couple of years now.