How do you check your engine oil? Silly question, right? Or is it?
There is always more to know than the obvious, checking engine oil sounds like such a no brainer but keep reading and I’m sure you will see there is more to it than just pulling out a dipstick.
What is engine oil & what does it do
Engine oil is the lifeblood of your engine and not only does it lubricate all the moving parts inside your engine but it also cleans away any abrasive debris created by these moving parts and the combustion process thus reducing excessive engine wear.
It does this by circulating oil around your engine and back to the sump essentially washing any contaminants down into the bottom of your engine sump where they can get removed from the system with your yearly engine oil change.
Engine oil also helps to transfer heat away from your engine, helping to keep temperatures stable.
How does engine oil differ from other oils?
There are many different engine oils available today all requiring different additives for different applications eg (diesel/petrol).
And while most of the basic functions of these engine oils remain the same, lubrication, cleaning and cooling, other oils required for your engine and driveline do differ quite a bit and are not cross-compatible for other components.
The science behind oil design and function is a huge topic and is beyond the scope of what I will talk about here.
A couple of examples of other oils and how they differ from engine oil are –
Power steering oil/fluid
Power steering oil differs quite a bit by being a type of hydraulic oil.
Gear oil
Gear oil has extreme pressure resistance and offers noise suppression aside from lubricating cooling and cleaning away debris from contact surfaces
As you can see oils are designed specifically for the intended application and as such always refer to your service/owner manual for correct oil requirements.
checking oil on dipstick
How to check your engine oil level
- Remove dipstick
- Wipe dipstick
- Dip dipstick again
- Check level
- Repeat 2, 3 and 4 a few times to confirm reading
Checking your engine oil level sounds straightforward but you would be surprised to know how many people are unsure of how to do it and what the markings on a dipstick tell you.
To check oil level correctly there are a few factors to take into consideration –
Manufacturer’s recommendations
Some manufacturers have specific steps for checking oil, so always consult your engine manual first if you are unsure.
Other manufacturers do not have any recommendations for oil checking so some basic mechanical skills and common sense will be required.
Have you done an oil change and is it the first start?
If you have just done an oil change and the oil is between the high/low marks you should now start your engine briefly to circulate oil through the engine to fill any new empty oil filters, 30sec or so should be long enough for this.
Now stop your engine and again dip the oil, you should find the oil level has dropped, this is due to the new oil filters filling with oil and some oil has circulated up and around the engine.
If you can, I would let your engine sit for a few minutes before checking again. This is just to let any oil from the upper parts of the engine travel back down to the sump.
This will give you a much more accurate measurement, if you were to check the oil straight after stopping and topped up then, you would find the level would creep up the dipstick overnight due to the oil in the upper parts of your engine not having sufficient time to make its way back to the sump.
So again start the engine for 30 sec, then stop the engine, then let the engine sit for a few minutes, then dip the dipstick for a more accurate reading, then top up oil as required.
Checking level with a cold engine
Checking the oil level on a cold engine will have a higher oil reading than a hot engine and this is because a lot of the oil from the upper parts of the engine has made its way to the sump raising the level.
Checking level with a hot engine
Checking the oil level on a hot engine will give a lower reading than a cold engine due to oil circulating up into the upper parts of the engine and not having time to run back down to the sump.
Dipstick markings and what they mean
Dipsticks typically have a high and a low mark and as you would expect oil at or below the low mark indicates the oil needs topping up.
And oil above the high mark indicates too much oil and some should be removed from the system.
Technically anywhere between the high and low marks (full and empty) is within spec, but obviously closer to the high side (full mark) would be optimal.
Another thing I often get asked is to do I read the high side or low side of the dipstick?
Now my answer is if the service manual or owners manual does not stipulate where it should be I would suggest reading the low side as the true reading.
My reasoning behind this is because a dipstick usually enters the sump at an angle and the higher oil reading on one side is actually going to be the lower side of the dipstick, as long as it is between the high and low marks on the dipstick technically the level is correct.
What happens if oil is low
Low oil causes engine damage, an engine has a recommended oil range for a reason and if you go below this capacity you are not providing the engine with enough lubricant to work efficiently and this can cause serious engine wear and in a worst-case scenario seize an engine.
What happens if oil is overfull
Overfilling can cause the engine oil in the sump to contact the crankshaft causing cavitation this results in the oil pick up in the sump not being able to efficiently pick up the aerated oil leading to oil starvation and ultimately engine failure.
One thing to remember here is every engine has different oil capacities and while being overfull on one engine may not cause any issue at all, other engines can be very sensitive to overfilling.
What to do if the engine is overfilled
When it comes to removing oil from a marine engine there is really only one option, you have to suck the oil out either with a hand pump, electric oil pump or onboard oil extraction pump.
To suck the oil out there is usually an oil hose for this purpose, these can be found exiting the sump somewhere and may need an adaptor fitting to allow your pump to attach to it.
Other places you can draw oil from is the oil dipstick tube and oil fill tube both of these tubes will give you access to the sump where you can suck oil from.
Checking your oil’s condition
Why is my new diesel oil black
Diesel engines create lots of soot and combustion by-products and this finds its way into your oil turning it black almost instantly, but don’t worry just because it looks black and dirty it doesn’t mean the oil is bad it just means the oil is doing its job and is cleaning away the abrasive deposits.
Water in oil
dipstick with rusty watery oil
If you have water in your engine oil it will quickly turn white and milky resembling a milkshake.
If you find yourself with water in your engine oil it’s time to make a visit to your local mechanic, this condition will require major work to rectify.
Rust on dipstick
Rusty dipsticks show moisture/water has or is entering your engine oil and again this will require a visit to your local mechanic for evaluation.
Metal on dipstick
Metal found on your dipstick, whether its little chunks or fine particles that look like glitter, is internal engine components breaking down from wear or component failure.
If you find any substantial metal on your dipstick consult your mechanic as soon as possible.
Can an engine make oil?
Yes, engines can make oil this is usually due to unburnt fuel getting past piston rings into your oil thus raising the overall engine oil in the sump, all engines will have some degree of fuel getting past piston rings but it shouldn’t be enough to raise the level on your dipstick substantially.
Another scenario for rising oil levels is coolant entering the engine oil from failed head gaskets, warped or cracked heads.
Engine losing oil
If you find every time you check your oil it needs topping up then there is a good chance you have an oil leak somewhere.
Oil sample testing
Oil samples are great for peace of mind and can indicate things like excessive internal wear and moisture ingress.
By doing oil samples, say once a year, what you are doing is creating an internal snapshot of how healthy your engine is and giving yourself a good indication of anything that may need attention either now or in the future.
Engine lubrication maintenance
The best maintenance for your engine’s lubrication system is simply following your manufacturer’s recommended service intervals and sticking to them.
By carrying out yearly oil changes as per the manufacturer’s recommendations you give your engine the best chance of long service life.
Conclusion
As you can see checking your engine oil isn’t as straightforward as you would expect, there are a lot of factors to consider like what oil do you use, when and how to check your oil level, does my engine have an oil leak or is there water in your oil?
By following my above-mentioned tips like regular servicing and oil samples you can stay ahead of the game and keep your engine happy and healthy for now and into the future.
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