Dipstick Readings

[aeromancfi]

I noted in a motocycle manual that measuring the oil level should be done "without screwing in the dipstick". It made me wonder about all the Lycoming O-320's, O-360's and my current IO-360 that have screw-in dipsticks. I've not seen any direction in any owners' manual, but it seems to me that there is about a 1/2-in difference in the readings between screwed in not.  Anyone know what the correct procedure is? and  does anyone have a printed reference?   

 

dancfi

[jetdriven]

I have never heard of anything that says not to check it screwed in.

[Jamie]

Related question. First flight of the day, how many remove the stick, wipe it, reinsert, pull it out and then look? Since I check the oil with the cap screwed in, I just unscrew it, pull it out and look.... no need to wipe it off.

 

This is correct IF you assume you check the oil level after screwing the stick back in.

 

good question...

[jetdriven]

If it has sat more than about 20 minutes, no need to remove-wipe-read.  just pull the thing out and see what it says.  If its over 5.5 QT, or 6.5 QT for flights over 4 hours, rock on.

 

Note, subtract a half quart from that reading if you are running straight 50 weight  oil if it has ran in the last day.

[Piloto]

To screw or not to screw. What a dilema. I just unscrew and read the dipstick without the need to remove it from the tube. No wipes and no drops. In fact never seen anyone wiping it to measure. 

 

José

[orionflt]

But here is the real question, are you on a level surface when you check your oil?

[Hank]

Both wingtips hit me in the same place when I walk around the plane. Must be level, right? Most often, it's still parked in the hangar.

[FlyDave]

If it has sat more than about 20 minutes, no need to remove-wipe-read.  just pull the thing out and see what it says.  If its over 5.5 QT, or 6.5 QT for flights over 4 hours, rock on.

 

Note, subtract a half quart from that reading if you are running straight 50 weight  oil if it has ran in the last day.

Byron - Why the subtraction?

[jetdriven]

Got the math backwards. Take the dipstick reading and add a half quart to that if running 50 weight oil. There will be a half a quart that hasn't drained back if it has been run recently.

[FlyDave]

Got the math backwards. Take the dipstick reading and add a half quart to that if running 50 weight oil. There will be a half a quart that hasn't drained back if it has been run recently.

Ah...makes more sense. Since I run 50 weight you had me wondering.

Thanks!

[Bob_Belville]

Got the math backwards. Take the dipstick reading and add a half quart to that if running 50 weight oil. There will be a half a quart that hasn't drained back if it has been run recently.

Have you confirmed that? 200 F 50W oil will not drain down out of a 400 F engine in the summer time in a few hours? 

[FlyDave]

Have you confirmed that? 200 F 50W oil will not drain down out of a 400 F engine in the summer time in a few hours? 

Yes - if I shut down and check the oil and come back the next day (24 hrs later) there will be 1/4 - 1/2 quart more. Summer or winter doesn't matter.

I guess 50 wt is pretty viscous!

[Bob_Belville]

Well, I can agree that oil sump will read higher the next day than it did immediately after shut down. (I think that's likely true with multigrade as well.)  Byron seems to me to be saying the oil level will still not be at equilibrium after several hours with straight weight.  

[aeromancfi]

Well . lots of comments, but I still haven't heard any definitive recommendation from  a manufacturer--- airframe or engine. Dancfi

[jetdriven]

Well, I have verified that if you let it drain for several hours, pour 7.0 quarts into the sump, then let it sit a few minutes and read the dipstick while screwed in, it reads 7.0 quarts as well.  it could be coincidence.

[Hank]

I noted in a motocycle manual that measuring the oil level should be done "without screwing in the dipstick". It made me wonder about all the Lycoming O-320's, O-360's and my current IO-360 that have screw-in dipsticks. I've not seen any direction in any owners' manual, but it seems to me that there is about a 1/2-in difference in the readings between screwed in not.  Anyone know what the correct procedure is? and  does anyone have a printed reference?   

 

dancfi

 

"Gee, Gomer, I ain't never heerd of nothin lack tha-yat." 

 

The last motorcycle I rode much had a separate oil tank that I just kept full; it would mix it with fuel all by itself [obviously 2-stroke]. That's not how I run my car or my Mooney.

 

I always check the oil in my car [every one I've ever owned] by fully seating the dipstick; the same for every airplane I've ever flown. While sitting on as level of a surface as I can find, which means not my driveway at home.

 

Counter-challenge:  can you provide any documentation from any airframe or aircraft engine manufacturer recommending not seating the dipstick when checking oil level? Or is it just the one motorcycle manual? In general, I would expect exceptions to general practice to be documented, which sounds like the one motorcycle did, but that does not mean that the rest of the engine world will suddenly start documenting what is standard practice. Especially for our planes, many of which probably predate that particular bike.

[N601RX]

I've saw several Honda products that specifically say to check the oil with the dipstick NOT screwed in. 

[carusoam]

Long chain molecules have a tendency to climb the stick during the rotation... Potentially leading to a slightly higher, false reading.

Deep theory from chem eng 102 .... Polymer rheology... The study of the viscosity of long chain molecules.

Best regards,

-a-

[Mooneymite]

You are all too picky.

 

Pull it out.  If there's oil on it, it hasn't all leaked out...yet.

 

Oh, wait.  That's from the R-1820 manual.

[jetdriven]

I've saw several Honda products that specifically say to check the oil with the dipstick NOT screwed in. 

I have that Honda lawnmower as well, but I fail to see how this is relevant to a Lycoming engine. And even if it was, we are talking about a 1/4 quart variance, or 8 oz.  The engine is certified to run on 2 quarts, although I am not inclined to run lower than 5. 

 

I suppose we could just ask Lycoming?

[AmigOne]

The measurement on the first flight of the day we do it from the "screwed in" dipstick so to me it makes sense to me that every other one should be made the same way. We all know how much our engine consumes normally and in long flights we should know when and how much to ad. Just finished a 38 hrs long flight around the USA and I knew that I had to add 1 qt every 9 hrs.

[wrench]

I noted in a motocycle manual that measuring the oil level should be done "without screwing in the dipstick". It made me wonder about all the Lycoming O-320's, O-360's and my current IO-360 that have screw-in dipsticks. I've not seen any direction in any owners' manual, but it seems to me that there is about a 1/2-in difference in the readings between screwed in not.  Anyone know what the correct procedure is? and  does anyone have a printed reference?   

 

dancfi

Was that on the center stand or kickstand? Should be different depending on which.

[BigTex]

You guys are really over thinking this... Why don't you guys just calibrate your dipstick? Change your oil, add 8 quarts and see where the oil hits the dipstick. If you want to measure with the dipstick unscrewed, unscrew it and measure.

[aaronk25]

You guys are really over thinking this... Why don't you guys just calibrate your dipstick? Change your oil, add 8 quarts and see where the oil hits the dipstick. If you want to measure with the dipstick unscrewed, unscrew it and measure.

No kidding! Dipsticks!

[M20F]

You guys are really over thinking this... Why don't you guys just calibrate your dipstick? Change your oil, add 8 quarts and see where the oil hits the dipstick. If you want to measure with the dipstick unscrewed, unscrew it and measure.

Run the engine first though so that there is oil in the filter or you will get a higher reading.