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Lycoming oil dipstick calibration ?

L

Larry DeCamp

Well Known Member
I had to shorten the dipstick tube to fit under the SJ cowl. Now I must shorten the dipstick and dowel it into position.
Two questions:
- Is the Lycoming calibration mark for Quarts poured into a dry crank case, or is it the mark for oil level AFTER oil has drained (or not drained) from the pump,filter, oil galleries etc. ?
- Does the Lycoming mark reference a level engine for trigear airplanes. Since I have the opportunity, I may mark the stick for tail dragger attitude and note it in the POH.
 
I often wondered about your first question and interested in the answer. I did calibrate my dipstick on my taildragger. It made about a 1/2 quart difference. I did it after 6 months of flying during a regular oil change so the system other than the oil filter was full. I poured in 4 quarts and then started the caibration at that point. I took a while to do as you have to wait for the quarts to fully drain into the sump. I warmed the oil in hot water to speed up the process however it still took overnight.
Looking back I'm not sure it was worth it in my case. The standard hash marks likely were fine. In the end you have to find a level that works for your engine. If your over filling it will blow out pretty quickly.
 
I used stock off the shelf Lycoming parts. When I tested calibration, it was accurate for oil in the oil pan and I have a tailwheel airplane so it was in the on the ground parked attitude.

About the only suggestion that I will make is to pay the extra money for a "Real Gasket" silicone gasket instead of using the stock paper gasket.
 
My engine came with no markings on the dipstick. I fully drained the preservation oil (about 24 hours IIRC), poured in 6 bottles of break-in oil in the normal tailwheel position on the ground, and put a mark there. When it gets to about 1/8" - 1/4" below that mark on the stick, I add a bottle. I guess it would be wise to add a 4 bottle mark on the stick someday.
 
rv8ch said:
My engine came with no markings on the dipstick. I fully drained the preservation oil (about 24 hours IIRC), poured in 6 bottles of break-in oil in the normal tailwheel position on the ground, and put a mark there. When it gets to about 1/8" - 1/4" below that mark on the stick, I add a bottle. I guess it would be wise to add a 4 bottle mark on the stick someday.
Click to expand...
Mine was not marked either, as I recall. And I had to modify the dipstick tube to get it to not rub on the engine mount and to fit under the cowling. I welded up a steel splice that shortened the tube and to cant it off at a slight angle. That made the dip stick itself too long so that also got shortened. Then I put 4 quarts in (after draining the sump including the suction screen [PITA]) and let it sit overnight. Marked that on the stick, added another quart, let it sit, marked that, then brought it up to 6 (which is all an O-320 needs; any more gets blown out) and marked that. I put a very shallow groove on with my tubing cutter, then carved a flat spot with a file and stamped the corresponding number of quarts on that flat spot with my metal number stamps. All of this done, of course, with the tail down. I need to pull the tube and put a new gasket at the bottom. The REAL gasket will bring it up about 1/8" but not enough to make that much of a difference in the readings on the stick. It's all pretty relative anyway......... 😊

I find it interesting that the O-320 Lycoming Operator's Manual states the "minimum Safe Quantity in Sump" is 2 quarts! 😳 I'm a 25 hour oil change guy but they also state that, with a full-flow oil filter system, that can be increased to 50 hours. That would make an interesting survey question...if it hasn't been done already.....
 
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The "safe quantity" of 2 qts only applies to MOST parallel valve engines. The angle valve engines with the wider sump require approximately twice as much.
 
Thanks for the feedback.
My real unknown is how much oil is typically in the pump, cooler,filter and galleries and does it drain back or not ? If it does, that oil would be included in the measurement on the dipstick, but not available for the pickup if the engine is running. Thus, how to define MINIMUM ??
For a parallel valve, it sounds like 4 quarts poured in an empty engine before first start and mark the stick, ???
 
Larry DeCamp said:
Thanks for the feedback.
My real unknown is how much oil is typically in the pump, cooler,filter and galleries and does it drain back or not ? If it does, that oil would be included in the measurement on the dipstick, but not available for the pickup if the engine is running. Thus, how to define MINIMUM ??
For a parallel valve, it sounds like 4 quarts poured in an empty engine before first start and mark the stick, ???
Click to expand...
On my airplane, it is between 2/3 and 3/4 of a quart in the rest of the engine.

Change oil and spin on filter. Add 7 quarts of oil. Run engine or fly. Back on the ground, it is down almost one quart. Over night, it is then reading between 6-1/4 and 6-1/3.

To the best of my knowledge, that does NOT account for the oil in the oil cooler.
 
Larry DeCamp said:
Thanks for the feedback.
My real unknown is how much oil is typically in the pump, cooler,filter and galleries and does it drain back or not ? If it does, that oil would be included in the measurement on the dipstick, but not available for the pickup if the engine is running. Thus, how to define MINIMUM ??
Click to expand...
On an O-320, that would be 2 quarts measured by the dipstick, I would assume. How else would one know..... :unsure:
Larry DeCamp said:
For a parallel valve, it sounds like 4 quarts poured in an empty engine before first start and mark the stick, ???
Click to expand...
Whatever oil that stays where it is in the internal parts of the engine, filter, pump, cooler etc, is going to stay where it is to an extent after it gets pushed there. If you fill an empty engine before all those areas are full of oil and mark the dipstick, your reading will not include all those areas that suck up the oil and stay there. What you want to know is how much oil is in your sump before you go flying. I would put 5 quarts in before first start and measure that from the tip of the dipstick. Don't mark it yet. Then put in the 6th quart and measure that. Then, after your first run, measure what is now in the sump having filled the rest of the engine. It will be below your measured 6 quart. If it is at the 5 quart measurement, add to bring it up to 6. That is what you want to know when you go flying as you will be monitoring oil consumption. After your first oil change, drain the oil including the (PITA) suction screen, put in 4 quarts and mark THAT on your dipstick. Add another quart if you want to know where 5 quarts is, then add the 6th quart and mark that. Now you will know how much oil is in your sump.
 
jrs14855 said:
The "safe quantity" of 2 qts only applies to MOST parallel valve engines. The angle valve engines with the wider sump require approximately twice as much.
Click to expand...
While this is a true statement, note that it does not apply to the parallel valve IO-360-M1B that many of us are using. It has a minimum safe oil quantity in the sump of 4 quarts.

i-PXKvCRk-XL.jpg
 
When I change oil and filter in my RV-4 with IO-360 I raise the tail to flying position and let it drain over night. The next morning I install new filter and add 5 quarts of oil, start the engine and check for leaks. Next morning check the oil lever and mark it with a tubing cutter applied to the dipstick. That is my add oil mark. Now add another quart to bring it up to 6 quarts and make another mark with your tubing cutter. My dipstick had two sets of marks, neither even close to accurate.
 
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