How much overfill can I get away with?
This is just my two cents...only my opinion...and not to be taken as gospel....
I agree with this opinion...
The issues with over-filling is that the crank slaps a ton of oil around and froths it up, which lowers lubricity and makes the oil aerated which doesn't pump well, and again you loose lubricity for the engine. Over the long term I believe it oxidizes the oil as well which breaks it down faster.
This is the first thing that I think about when it comes to overfilling...
The fly in the ointment is...we never know how much oil is really in the engine with measuring it only with a dipstick and dipstick tube...
....manufacturing tolerances and assembly errors inherent with mass manufacturing keep us from knowing truly if the oil level is low enough to not get slapped by the crank and rods with the truck on level ground...much less a grade...the only way to be sure is to have the oil pan off and stick the stick in the tube and see where it is....
This is a reason to have a good grade of oil in there that resists aeration and frothing...extra insurance against oil pressure loss intermittently...which can wipe your bearings, crank, cam, lifters, etc.,etc.
Ideally...we should have sight plugs at the right level in the oil pan...but that would be costly and also require people to actually get underneath the truck to read the sight plug...not a good idea when it comes to limiting potential liability.
Also the engine running level is going to be different from the engine not running level...and...it reads differently after sitting a while than when you just shut it off...
So...we are stuck with trusting the crosshatch on the stick after we change the oil and check it...personally...I would run my oil in the middle of the cross hatch....thermal expansion will raise the level somewhat...and call it a day....and then check it occaisionally under different conditions to get a 'feel' for how it acts...
The stock gauge is junk, if that's the one you mean.
as @Cubey said, you won't see the difference on the dash gauge. I guess it's possible you could if you have the old style sender that actually works but there aren't numbers on the background of the gauge...
On this...somewhere between the 40's, 50's 60's and now...there is probably buried in the law books and court records of some nit wit that sued Ford over their oil pressure readings on a fairly new automobile and was just not willing to believe that 10 PSI per 1000 RPM was good enough to last 100K miles...or...whatever the warranty was...
So....I believe that Ford responded with making an oil pressure guage system that was general...and not specific...so...I imagine that your readings...when the engine is running...is going to be always somewhere between the 'N' and 'L' in the word NORMAL...
Same with the coolant temp guage...although I found out last summer while towing a heavy load.... that I could cool my engine better with the windows down and the heater on high...
As long as my guages move when my engine is running...I am not worried...I also have an aftermarket guage that came with my truck and it usually reads around 40 PSI...so...I am ok...
Pre-filling the oil filter is always a good idea...you don't want too big of an air bubble moving through your lubrication system for too long...
the white stuff later and it was like a gob of whale snot.
I have seen that in diesel fuel tanks, too...I imagine it might be a form of algae or other contaminant...it stopped a few engines cold...when it would not allow fuel to flow...
Hope this helps...again...just my .02