How do you read your engine oil dipstick?

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How do you read your engine oil dipstick?

Postby SubaruDIY20 » Mon Aug 28, 2023 9:06 am

Does anyone else find that their engine oil dipstick gives a different reading depending on which side of it you look at?

One side of the stick will have a clearly defined line which i think is from where it was submerged in oil, and the other side has a smear of oil which always gives a significantly higher reading. The difference is huge - the side with the clearly defined line would read above the low level indicator (within acceptable range); and the smeared side would read past the high level indicator (indicating an overfill).

I would rotate the orientation of the dipstick and the sides with line and smear change.

I am guessing, one side that has the smeared oil is due it to coming in contact with the internal sidewall of the engine so gives an incorrect reading (not the reading you take).

Maybe a dumb question but i ask anyway :lol:
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Re: How do you read your engine oil dipstick?

Postby Yowie » Mon Aug 28, 2023 8:23 pm

Fair question.

Assuming the dipstick is clocked correctly/normally ("D" finger handle facing forward, oil can icon looking normal) the crank side has the markings and the passenger side cops the outside of the dog leg of the dipstick tube on its way to the sump.

I suspect the non-marked outside of the dipstick end collects extra oil from touching the outside of the dogleg bend, so should be disregarded.

[EDIT - the above info based on an EJ25. 2 litre experience may vary]
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Re: How do you read your engine oil dipstick?

Postby bigBADbenny » Sat Sep 02, 2023 10:39 am

Oil check, Subaru H4:

I get accuracy from making it a weekly (or monthly, once oil consumption has been eastablished) ritual/habit:

Fully warm up the engine, eg on the way to the servo.

Preferably your service station, garage (or parking spot) has a level surface, this helps for a consistent and accurate oil level check.

Pop bonnet and fuel door.
Open & prop bonnet.
Loosen oil cap to speed up oil drain back to the sump.

Fill your car with fuel, in the fuel tank.
(This will allow a little time for your oil level to settle.)

Close oil cap.
Remove dipstick,
wipe dipstick clean,
pull up 1”,
then pull and read level,
on the high side. (Or low side, or split the difference, as per your preference)

The oil amount between high and low marks is 1 litre/1.057 us liquid quarts.

The notch indicates oil level “full”, with a warmed up engine.

Don’t loose the oil cap oring. The oring seals the cap to the crankcase, if it’s missing or cracked or shrunk, an air leak will affect pcv system performance and affect fuel trims etc.

The same applies for the dipstick oring on the handle, it should be a fairly tight fit.

The dealership should have spare orings, or try your local engineering supply shop.

So when I first pull the dipstick, the oil is very high on it.

But after a wipe and the correct reinsertion and reading method the true level is shown, as long as the oil has had time to drain back to the sump.

If in doubt, it’s fine to split the difference between the low and high sides of the dipstick.

Having the car on level ground and letting the warm oil drain to the sump is the key as Matt mentioned, let the oil settle for 5-15 minutes.

Check your oil cap and dipstick orings are present and that they seal. Eg if you have oily blowby under the oil cap, it’s not sealing, get a new oil cap or replace the seal.

The hot to warm level difference is only around 5mm as mentioned above but colder oil will take longer to settle.

Anyway consistency is the key.

If the car has heightened oil use but without obvious external oil leaks, it’s a good idea to do a comprehensive inlet pressure test.

By adding 1psi regulated air and smoke to the inlet pipe, engine off test, you’ll get (eventually) to any inlet tract, pcv system and crankcase/valve cover air leaks.

Generally a leaking pcv system or sticky pcv valve will result in compromised blowby control and excessive oil use.

Cleaning or preferably replacing the pcv valve and using clamps on its hose is good practice.

Over filling oil: more than 6 litres of oil in the sump might be an issue.

If the oil was indeed overfilled, then the crank might have created a heavier than usual oil mist that would have entered the pcv valve via the pcv stack at the rear of the engine block.

So getting to the pcv valve to clean it might become a priority, especially if the car blows smoke under boost or at high rpm.

The info is the result of maintaining a high km lib that uses oil.

When everything is sweet, it’s at the rather generous factory oil consumption limit,
when it has issues eg sticky pcv or lost oil cap oring oil consumption jumps right up to say a litre per 500km!
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