Oil dip stick accuracy

[Ronald P]

We inherited a 2011 SEL 3.5 Edge with 40K.  First oil change I carefully measured out the specified 5 1/2 quarts.  After driving it a few miles and letting it sit overnight it measured a quart low on the dip stick.  It had indicated full before changing so I measured the old oil.  The drained oil  measured nearly 6 1/2 quarts.

[Edgingage]

Aha! Finally somebody else asks the question I've been hesitant to ask for a long time now.

I own the exact same type of vehicle, only with almost four times your mileage.  I don't have the ownre's manual in front of me right now, but if I remember correctly it reads 5.2 L capacity with every oil & filter change (sorry for the international units, that's what they use for Canada).  So, I always buy a 4.73 L jug and a 960 mL (0.96 L) bottle.  I dump the whole jug plus half the bottle (0.48 L).  That makes a total of 5.21 L, exactly what the book reads.  However, when I measure it, the oil level is at the bottom line mark on the he stick.  Then I add the remaining of the bottle (another 0.48 L) for a total of 5.69 L, and STILL doesn't reach the top line mark on the stick (the way I like to leave it at every change).  I still have to add another 300 and some mL to get the oil level reaching the top line mark on the stick.

I know the containers are not accurate to measure.  This last change I used a 1000 mL graduated cylinder to measure the exact oil I added after emptying the 4.73 L jug.  And I also know that once in a while a container may not contain what it reads, but I've owned this car for over three years now and it's been exactly the same since first oil change.  The good thing is that, by the time of the next oil change (six months later), the oil level is at the bottom line mark of the stick (no top up needed between changes )

The questions I wanted to ask for a long time were: how do we know for sure that the oil stick is correctly calibrated?  Could it be defective, a factory mistake?  Am I /are we (now;) adding to much oil to the engine thus risking to damage the catalytic converter?

 

Thank you Ronald for taking the lead on this worrisome (to me) subject.

Edited December 14, 2020 by Edgingage
Grammar

[WWWPerfA_ZN0W]

fluid capacity is 6 quarts.  and how much you put in will depend on how much you take out. but have not heard of issues with dipstick accuracy on the 3.5/3.7L engines.  on the 2.0 ecoboosts in gen 2+, yeah, it can be a PITA.