Check oil-----when??

[jdoran]

I recently learned that on cars, they changed the markings on the dipsticks to reflect a warm/hot reading because they knew that everyone only checked their oil after driving to the gas station.

I'm curious about what you all do when checking oil in the plane:

Do you go by the dipstick reading after the engine has been sitting (say overnight), or do you use the reading you see after you've had the engine running, (even if only for a few minutes)?

There is a few quart difference between the two readings.

I have the O-200 in the F-19.

[Guest]

Re: Check oil-----when??

Hi John,

I am not convinced that you or I could spot the difference in the hot/cold readings. I bet it expands very little, certainly not quarts.

As pilot doing a proper preflight inspection you should check it before you fly regardless of temperature.

Dave

[flybikefarm]

Re: Check oil-----when??

Next time you change oil, if you don't have a filter to contend with use the mark after you fill with new oil as your cold full level. George

[jdoran]

Re: Check oil-----when??

I don't think it's the difference between hot and cold as much as it is that the oil has time to drain back out of the oil galleys in the engine, and back down into the tank.

No kidding, there is at least a one quart to 1-1/2 quart difference.

[Len Petterson]

Re: Check oil-----when??

Just keep im mind what any fluid have surface tension and cold oil has a dendency to "crawl" up the stick and it may looks like you more then what you have.
So look at it as you first take it out clean the stick and read it again. It can make a good bit difference, 1/4 of quart, or shall I top up or not.
Len

[Guest]

Re: Check oil-----when??

Good points about draining and surface tension.

I usually wipe the dipstick too.

The post mentioned temperature so I went with that, I see you are really talking drained though.

By the way I 've been flying old airplanes since 1966 and I never heard this before. So I am skeptical, maybe there are clogged up return paths? I suppose I could have missed out on this.

So what do you do then when you do a x-country and land at the destination, check your oil after landing and it reads 1 to 1-1/2 quarts low while you refuel?

Would you fly off with 2-1/2 quarts in the sump?

I would add oil.

I am still skeptical that an engine in good shape will hold 1 to1-1/2qts of oil "above".

I bet it would hold 8 or 12 ounces "above" and take a few minutes to drain the last few ounces.

Wonder if the manual gives the "above" sump capacity (rocker covers, galleys, case cavities?

Dave

[3Dreaming]

Re: Check oil-----when??

I could see this much of a swing, if you are not wiping your dip stick when checking cold. I've seen them read as much as a quart over what they are because of the oil climbing the dip stick. When it has just been run you have to wipe it because it is all covered. Also cars use a 5W30 or 10W40 oil which will drain more easily to the sump. Most of the older aircraft use a 50W oil which is slower to drain back to the sump. Tom

[flyguy]

Re: Check oil-----when??

On my -85 the oil will climb up the dipstick as much as 2 quarts with it just sitting there cold. I calibrated the dipstick when I first bought the plane.

Additional note just noticed yesterday. Pulled engine off mounts. Had not been run for a week or so.
When I removed the pressure sensor a considerable amount of oil drained from the fitting. Considering what went on the floor and what I caught in a can I would guess about 1-1/2 inches in a large peach can (29 ounce.) Surprised me that there was that much left in the upper part of the engine.
Darryl

[Ragwing nut]

Re: Check oil-----when??

I always check cold during preflight. Won't do you no good to check it after you have gone flying.