inconsistent oil level measurements with O470R locking dipstick

[GeorgeC]

I thought I knew how to work a dipstick, but apparently you learn something every day.

The 182 I fly has a dipstick that locks when the handle loop faces upward. So, to check it, I first rotate CW 180 to unlock, remove, wipe, insert, rotate CCW 180 to lock, rotate CW 180 unlock, remove, and read the oil level. When done this way, I get a reading of 9 qts.

If I do it the other way, e.g. first rotate CCW 180, I get a reading of 10 qts.

Which is correct and why? I assume the tiedown is not perfectly level and/or the dipstick is not perfectly straight, so you get a different reading if the dipstick sweeps out the left half of a circle vs. the right half, so the true level is 9.5...

 

[455 Bravo Uniform]

Make sure your tube is firmly bottomed out and tight. Dipstick readings puzzled me for a number of flights until one time I couldn’t completely close the access door cuz the dipstick was in the way. Just something to confirm and eliminate as a possible cause.

 

[Cap'n Jack]

This suggests you keep it at least a quart higher than the minimum oil level mark.

 

[Sinistar]

We have had a lot of problems with out nose strut on our 182P model. Given the exact same level parking spot....nothing will give you more erratic (static) oil level measurements than the front strut height. If I air it way up the oil will look kind high. If the strut is bottomed out I swear it will look more than a quart low.

Before chasing problems with the engine or even the dipstick, make sure you get the same angle of the plane (parked) and then compare.

 

[GeorgeC]

Make sure your tube is firmly bottomed out and tight. Dipstick readings puzzled me for a number of flights until one time I couldn’t completely close the access door cuz the dipstick was in the way. Just something to confirm and eliminate as a possible cause.

The dipstick is fully inserted in the tube, are you suggesting the tube itself may be loose?

 

[455 Bravo Uniform]

The dipstick is fully inserted in the tube, are you suggesting the tube itself may be loose?

Exactly, dipstick tube needs to bottom out into the crankcase, and the hold-down needs to be tight. Just something to check. If the tube is not bottomed out, oil will appear low on dipstick.

 

[GeorgeC]

Good to know, thanks. I don't think that's the case here, since I can check it back to back and get the discrepancy above. At least it's consistently inconsistent...

 

[Mtns2Skies]

This exact thing happens to me too, I always just kept my oil high just-in-case, but of course it spits it all out onto my belly.

 

[Sinistar]

I wonder if the direction you turn the dipstick lock has a small amount of thread (as part of the lock) and when you start it the CCW direction first and end with CW to all the way in it gets in a bit deeper. But I don't recall any threads so maybe its more of a spring clip (plane is too far away to look) and going one way allows it to go under it vs above it?

I have to try this next time. I have always just went one direction. Its like I just discovered another dimension

 

[GeorgeC]

It's not threaded, there's a D-shaped spring clip that engages a groove that's machined in the dipstick.

 

[Stewartb]

Checking oil, dipping tanks.... it's an indicator. Learn what it means and do it the same way EVERY time.

 

[Dan Thomas]

The dipstick probably has a curve in it that puts the end farther into the oil in one position than in another. That dipstick tube doesn't support the stick all the way down into the oil, after all. And you only need to turn the stick a quarter-turn to unlock it, not a half-turn.

 

[455 Bravo Uniform]

The dipstick probably has a curve in it that puts the end farther into the oil in one position than in another. That dipstick tube doesn't support the stick all the way down into the oil, after all. And you only need to turn the stick a quarter-turn to unlock it, not a half-turn.

I think that makes sense.