Dip Stick Markings

[Mark Dickens]

So, I have a "Bob Engine" and discovered that the dip stick has no markings on it. It's an IO-360. Yes, i can add oil a quart at a time and assume "full" means 8 qts or some thing like that...anyone else have this issue when buying from Bob? I might call Mike Meador and ask him, but I doubt they have records to refer to. Some time ago, I called and asked Bob what model engine the case came from and his response was "why do you want to know?"...hmmm

[jaredyates]

Hi Mark. Our first engine was from Bob, and also didn't have any markings on the dipstick. I did as you described, which is to add quarts, let the oil settle, and mark the dipstick. That worked just fine. Our current engine is a factory Lycoming. It's marked every three quarts, which also works fine. I don't really have any concept for "full" when it comes to Lycoming oil levels. If you add too much and run the engine, it will vent the excess overboard and return itself to where it wants to be. The range between that point and not having enough oil is probably something like 4 or 5 quarts.
I think of Lycoming oil levels much like EGT values, in that their absolute value is not meaningful at all, but their relative value and their trend is what really matters. Honestly, you could label the dipstick with letters if you wanted to, although it is nice to have a sense of how much oil you'd like to add to get up to a level that you have in mind. I find if I'm adding more than a quart at a time, it probably means I went too long without checking. But there's also a lot of inaccuracy on the dipstick. A change in the level of the parking position, either left-right or front-to-back, or a change in tire size, can all upset the norms for your usual dipstick levels.
Even if nothing changes as far as the attitude of the plane, you'll also find a lot of fluctuation of the dipstick level, which is indicating the oil in the sump, because the oil isn't always in the sump. It's also in lines, passages, the oil cooler, the propeller, and all of those kinds of places. Some folks find that right after an engine run, the sump level is its lowest, and then a day or two later, the sump level rises as that oil settles back into the sump. It's probably not accurate to assume that the total amount of oil in the engine correlates to any numbers on any dipstick of any engine.

[Nev]

Mark, mine was the same. I added two quarts at a time and marked the dipstick with an engraver. As Jared mentioned, it's more art than science.

[Mark Dickens]

Mark, mine was the same. I added two quarts at a time and marked the dipstick with an engraver. As Jared mentioned, it's more art than science.

Agreed, I was just surprised that it hadn't been marked

[alaskabearhawk]

FWIW, my dipstick has markings from the factory, but the markings are for a level installation. I wanted to know two things. First, I wanted to know how accurate the markings were at level. Second, I wanted to know how the oil level changes at a 3pt attitude.

I made a tailwheel lift so I could check it, raising and lowering the tail as I added oil one quart at a time. The factory 3 quart interval markings are very accurate. Then I made a note card of where the levels are with the tail on the ground. Because I will be going on floats (close to level), I now have two references. As an aside, I also used the opportunity to calibrate my fuel sight gages at 3pt and level flight.

Lastly, and most importantly after break-in, I determined the “happy spot” for my engine. Most aircraft that I have flown have an oil level where it likes to be. Excess oil is just vented overboard until that “happy spot” level is reached, then it just stays there. I can then accurately keep track of oil consumption. For my engine at oil changes I use 9 quarts of oil and 14.4oz of Camguard. The engine uses very little oil and I have never needed to add oil between changes. Like Jared noted, my oil level increases about 1/8th of an inch after it sets for a few days.

The two takeaways for me in this exercise are that I know how much oil I need for an oil change and I also know where the starting point of a fresh oil change is on the dipstick. That way I can monitor the trend of oil use and not just guess. If it were my engine, I would find the happy oil level and mark it. I would then find the level at one quart lower and mark that.

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[Utah-Jay]

My “Bob” dipstick was the same

I added some notches, but the level the engine likes the level I have some stamped lettering and I use that as my normal level. I have an O-360 and my engine seems to like 5 quarts.