BakerBoy
It's all small stuff.
To the OP, many overworry about overfilling... or what brand or viscosity...
I wouldn't be concerned if it had say, 4.5 quarts. I have overfilled mine--within seconds of startup, the oil is no longer visible in the sight glass. And it didn't blow up after running a whole campaign with some extra oil in the crankcase, nor has it failed in some related way many years later. I'm now in the habit of pouring in 1 gallon and not worrying about it (as long as I see oil through the sight glass).
Consider that it takes a minute or two for the majority of oil to return to the sump after shutting down the engine to be visible in the sight glass (yet it only takes seconds to pump the oil out of the pan). What happens before the oil dribbles back into the pan?? (Rhetorical question). The oil pump has pumped most of the available oil up (therefore, draws some air in), and my opinion is a extra few ounces of oil in the crankcase doesn't have negative consequence (the crank/rods don't splash in it, except perhaps the first few seconds when starting up the engine). On the contrary, having less time that the oil pump draws in air is likely better.
So, I can envision someone asking: Why doesn't Honda recommend more oil than 4QT? Because they've decided 4QT is good enough (and is of a commercially common available size increment: the quart).
My guess is that the engine does just fine with 5QT in it, perhaps even 6QT. But I've no need to try to increase volume to cause a failure.
But it's your engine, so you decide whether a few ounces over 4QT is too much.
A related point: the slight less air volume in the crankcase (slight increased oil volume) does not cause more internal pressure in the crankcase. Regardless of oil volume, the temperature of the air in the crankcase still stabilizes at the same temperature, but there's less mass of air to expand (as it was displaced by slightly more oil volume). Even if the ST crankcase were a sealed vessel, air pressure in the crankcase would be actually slightly less with more oil. But the point is moot: the ST uses crankcase gas recirculation and uses a non-sealed crankcase. Hoses pull the oil-misty crankcase air from the valve covers up into the air box for consumption as fuel. Many of us find oil in our airboxes where that hose connects.
I wouldn't be concerned if it had say, 4.5 quarts. I have overfilled mine--within seconds of startup, the oil is no longer visible in the sight glass. And it didn't blow up after running a whole campaign with some extra oil in the crankcase, nor has it failed in some related way many years later. I'm now in the habit of pouring in 1 gallon and not worrying about it (as long as I see oil through the sight glass).
Consider that it takes a minute or two for the majority of oil to return to the sump after shutting down the engine to be visible in the sight glass (yet it only takes seconds to pump the oil out of the pan). What happens before the oil dribbles back into the pan?? (Rhetorical question). The oil pump has pumped most of the available oil up (therefore, draws some air in), and my opinion is a extra few ounces of oil in the crankcase doesn't have negative consequence (the crank/rods don't splash in it, except perhaps the first few seconds when starting up the engine). On the contrary, having less time that the oil pump draws in air is likely better.
So, I can envision someone asking: Why doesn't Honda recommend more oil than 4QT? Because they've decided 4QT is good enough (and is of a commercially common available size increment: the quart).
My guess is that the engine does just fine with 5QT in it, perhaps even 6QT. But I've no need to try to increase volume to cause a failure.
But it's your engine, so you decide whether a few ounces over 4QT is too much.
A related point: the slight less air volume in the crankcase (slight increased oil volume) does not cause more internal pressure in the crankcase. Regardless of oil volume, the temperature of the air in the crankcase still stabilizes at the same temperature, but there's less mass of air to expand (as it was displaced by slightly more oil volume). Even if the ST crankcase were a sealed vessel, air pressure in the crankcase would be actually slightly less with more oil. But the point is moot: the ST uses crankcase gas recirculation and uses a non-sealed crankcase. Hoses pull the oil-misty crankcase air from the valve covers up into the air box for consumption as fuel. Many of us find oil in our airboxes where that hose connects.
