Checking your engine oil is the single most valuable under-bonnet habit a driver can develop. It takes about two minutes, requires no tools, and can prevent the kind of engine damage that costs thousands to repair. For learner drivers, it is also a skill the RSA examiner will specifically ask you to demonstrate on test day — so knowing where the dipstick is and how to read it is not optional.

Source & Credit: Based on RSA Rules of the Road (Section 4: Vehicle Safety) and RSA driving test technical check requirements. The RSA requires drivers to check oil regularly and be able to demonstrate the check on request. Official resources at rsa.ie. BP Driving School is an RSA-approved ADI in Swords, North Dublin.
Vehicle Safety & Pre-Drive Checks — Article Series
In This Guide
  1. Why Engine Oil Matters
  2. What You Need Before You Start
  3. How to Check Engine Oil — Step by Step
  4. Reading the Dipstick — Diagram
  5. What Oil Colour Tells You
  6. How to Top Up Engine Oil
  7. What If My Car Has No Dipstick?
  8. Warning Signs to Take Seriously
  9. Engine Oil and the RSA Driving Test
  10. Common Mistakes to Avoid
  11. Frequently Asked Questions

Why Engine Oil Matters

Engine oil performs several critical functions. It lubricates the hundreds of moving metal parts inside the engine, preventing them from grinding against each other. It also carries heat away from parts the cooling system cannot reach, and holds combustion deposits in suspension so they can be removed during a filter change rather than building up on engine components.

When oil level drops too low, metal surfaces that should be separated by a film of oil begin to contact each other directly. The resulting friction generates extreme heat and wear. If the level drops critically low, serious and irreversible engine damage can occur within minutes of driving.

The oil warning light is not a "top up soon" notice. If the red oil warning light (oil can symbol) illuminates on the dashboard while driving, it indicates critically low oil pressure — not just a low level. Pull over safely as soon as possible and switch off the engine. Do not continue driving. Serious engine damage can occur within minutes.

What You Need Before You Start

  • A clean cloth or paper towel — to wipe the dipstick between readings
  • The correct engine oil for your car — if you may need to top up (check spec in the owner's manual before buying)
  • A funnel — makes adding oil cleanly much easier, especially in a tight engine bay
  • Your owner's manual — if you are unsure where the dipstick or oil filler cap is located in your specific car
Critical starting condition: the engine must be switched off and the car must be parked on level ground. Checking on a slope gives an inaccurate reading. Checking with the engine running is dangerous and gives a false reading. If you have just driven, wait at least 5–10 minutes for the oil to settle back into the sump.

How to Check Engine Oil — Step by Step

1Park on level ground and switch off the engine

Find a flat surface. Apply the handbrake. Switch off the engine completely — do not check oil with the engine running.

2Wait for the engine to cool if recently driven

If you have just driven, wait 5–10 minutes. This allows the oil to drain back into the sump, giving an accurate level reading. Checking immediately after driving can show a falsely low reading. The ideal time to check is before the first journey of the day.

3Open the bonnet and locate the dipstick

Release the bonnet catch (usually a lever under the dashboard on the driver's side), then release the secondary catch at the front of the bonnet. Prop the bonnet open. The dipstick has a brightly coloured handle — typically yellow or orange — and is located in the engine bay. If you cannot find it, consult your owner's manual.

4Pull out the dipstick and wipe it clean

Grip the handle and pull the dipstick all the way out. Wipe the entire lower portion clean with your cloth or paper towel. This step is essential — the first reading is always inaccurate because oil coats the stick as it is pulled out through the tube.

5Reinsert the dipstick fully

Push the dipstick all the way back into the tube until it seats fully. If it does not go all the way in, pull out slightly and try again — it follows a curved path in many engines. An incompletely inserted dipstick gives a false reading.

6Pull it out again and read the level

Remove the dipstick a second time and hold it horizontally. Look at where the oil film ends in relation to the MIN and MAX markers at the bottom of the stick. See the diagram below for how to interpret the reading.

7Check the oil condition as well as the level

While the dipstick is out, look at the colour and consistency of the oil (see the Oil Colour section below). Fresh oil is amber. Very dark, thick or contaminated oil — regardless of level — may indicate the car is overdue a service.

8Reinsert the dipstick securely and close the bonnet

Push the dipstick fully back in. Ensure it is seated correctly — a loose dipstick can be blown out by engine pressure when driving, causing oil to spray inside the engine bay. Close and latch the bonnet.

Reading the Dipstick — Diagram

Dipstick Readings — What They Mean
Dipstick oil level readings — too low, correct, ideal, overfilled Too Low MAX MIN ❌ Add oil Below MIN Low — Top Up MAX MIN ⚠ Top up soon At MIN mark Correct ✓ MAX MIN ✓ No action needed Between MIN–MAX Overfilled MAX MIN ❌ Too much oil Above MAX — remove
Four possible dipstick readings: below MIN (add oil immediately), at MIN (top up soon), between MIN and MAX (correct — no action needed), above MAX (overfilled — do not add more, have excess removed). Always read with the dipstick held horizontally after the wipe-reinsert-pull sequence.
Overfilling is harmful too. Oil above the MAX mark is not "extra protection." Excess oil can be drawn into the combustion chambers, create excessive crankcase pressure, and foam — reducing its lubrication effectiveness. If you have accidentally overfilled, have the excess oil drained by a garage.

What Oil Colour Tells You

The level tells you how much oil is present. The colour tells you something about its condition. Both matter.

Amber / Golden

Fresh or relatively new oil. Healthy colour — indicates recent service or low mileage since last change.

Dark Brown

Normal used oil. Has collected normal combustion deposits. Still serviceable — a common colour for oil mid-service life.

Very Black / Sludgy

Overdue a service. Oil has broken down and collected excessive deposits. Book a service. Still drive carefully if level is fine.

Milky / Greyish

⚠ Possible coolant contamination or head gasket issue. Do not drive. Have inspected by a mechanic immediately.

Under the Bonnet — Key Oil Check Locations
Under bonnet diagram showing dipstick handle, oil filler cap and coolant reservoir locations Engine Block OIL Dipstick Yellow/orange handle 🛢 Oil Filler Cap Oil can symbol on top COOL- ANT Coolant Reservoir MIN/MAX markings on side Battery
Three key under-bonnet locations: the dipstick (brightly coloured handle — pull, wipe, reinsert, read), the oil filler cap (marked with an oil can symbol — used for topping up), and the coolant reservoir (translucent tank with MIN/MAX markings). Know where all three are in your specific test car.

How to Top Up Engine Oil

If the dipstick shows the level is at or below MIN, top up carefully. Add a small amount at a time — it is easier to add more than to remove excess.

1Confirm the correct oil specification

Check your owner's manual or the label on the existing oil filler cap. Common specifications include 5W-30, 5W-40 and 0W-20. Using the wrong specification can cause increased wear. If in doubt, check a motor factor — they can look up the correct spec for your registration number.

2Locate and remove the oil filler cap

The oil filler cap is on top of the engine, usually marked with an oil can symbol. Unscrew it anticlockwise and set it aside somewhere clean — do not place it on a dirty surface.

3Add a small amount using a funnel

Insert a funnel into the filler hole. Pour in no more than 500ml at a time. Engine bays are tight and oil is difficult to clean up — a funnel prevents spills over hot engine components and hoses.

4Wait and check again with the dipstick

Wait a minute for the oil to settle, then repeat the full dipstick check (wipe, reinsert fully, pull out, read). If the level is now between MIN and MAX, no more oil is needed. If still low, add another 500ml and repeat.

5Replace the filler cap securely

Screw the cap back on clockwise until it is firmly closed. A loose oil cap causes oil to spray around the engine bay at speed. Close the bonnet fully until you hear it latch.

Under-bonnet checks covered in EDT Session 1

BP Driving School walks you through oil, coolant, washer fluid and all technical checks from your very first lesson — RSA-approved, North Dublin.

What If My Car Has No Dipstick?

Some newer vehicles — particularly European models from around 2010 onwards — have replaced the traditional dipstick with an electronic oil level sensor. On these cars, the oil level is displayed on the instrument cluster or infotainment screen, typically accessed through a vehicle information menu.

If your car has no dipstick, check the owner's manual for the correct procedure. The RSA examiner is aware that some vehicles operate this way and will ask you to demonstrate the electronic check instead.

Test day note: whether your car has a dipstick or an electronic sensor, you must know how to check the oil level in your specific test vehicle. If using a school car for the test, your ADI should walk you through the car's specific procedure before test day.

Warning Signs to Take Seriously

Do not ignore the following — each can indicate a serious underlying problem:

  • Oil warning light (red oil can symbol) — indicates critically low oil pressure. Pull over immediately and switch off engine. Do not continue driving.
  • Dipstick reading below MIN — top up immediately. Investigate why the level has dropped (slow consumption vs rapid drop suggests a leak)
  • Oil puddles or drips under the car — indicates an external oil leak. Have it inspected before the next journey
  • Burning smell from the engine bay — can indicate oil leaking onto hot engine components
  • Blue smoke from the exhaust — may indicate oil burning in the combustion chamber
  • Milky or grey oil on the dipstick — possible coolant contamination / head gasket failure. Do not drive. Get it inspected immediately.
  • Unusual engine knocking or rattling sounds — can indicate inadequate lubrication due to low oil level or pressure

Engine Oil and the RSA Driving Test

Engine oil is one of the technical checks the RSA examiner will ask you about at the start of your driving test. You must be able to:

  • Show where the dipstick is located in your test car
  • Explain the correct procedure for checking oil (engine off, level ground, wipe-reinsert-read)
  • Show where the oil filler cap is
  • Explain how you would top up the oil if the level were low
  • Know what oil specification your test car uses
Preparation tip: practise this check in the actual car you will use for your test — ideally with your ADI during a lesson. Dipstick location varies significantly between car models. Hesitating on test day because you cannot find the dipstick is an avoidable fault. Know exactly where it is before you arrive at the test centre.

Common Mistakes to Avoid

Not wiping the dipstick before the first read

The most common mistake. Pulling the dipstick straight out and reading it gives an inaccurate result because oil coats the stick as it is pulled through the tube. Always wipe, reinsert fully, pull out, then read.

Checking on a slope

A car parked on a slope tilts the oil in the sump to one side. The dipstick may show too high or too low depending on which way the car is tilted. Always check on level ground.

Checking immediately after driving

Oil circulates around the engine while running and takes a few minutes to drain back into the sump. Checking too soon can give a falsely low reading. Wait at least 5–10 minutes after a journey, or check before the first drive of the day.

Overfilling the oil

More oil is not better. Oil above the MAX mark creates excessive pressure in the crankcase, can cause oil to foam, and may damage seals. Always add in small amounts and recheck frequently. If overfilled, have the excess removed.

Using the wrong oil specification

Different engines require different viscosity grades and additive packages. Using the wrong specification can increase wear or damage seals. Always verify the correct spec in your owner's manual before buying or adding oil.

Frequently Asked Questions

Always check with the engine switched off and cooled down. The ideal time is before the first journey of the day, or after waiting at least 5–10 minutes following a drive. Checking while hot or with the engine running gives an inaccurate reading and risks burns from hot engine components.

The dipstick is located under the bonnet and has a brightly coloured handle — most commonly yellow or orange — so it stands out. If you cannot find it in your specific car, check the owner's manual, which will show the engine bay layout with the dipstick marked. Know its location in your test car before test day.

Some darkening of oil is entirely normal — oil collects combustion deposits as it works. Dark brown oil is generally fine. Very black, thick or sludgy oil suggests it is overdue a service. Milky or greyish oil is a warning sign of coolant contamination and requires immediate professional attention — do not drive.

No. Use only the oil specification recommended for your specific engine — found in your owner's manual, on a sticker under the bonnet, or on the oil filler cap. Common specifications include 5W-30, 5W-40 and 0W-20. Using the wrong grade can increase wear or damage engine components.

The red oil warning light indicates critically low oil pressure — not just a low level. Pull over safely as soon as possible, switch off the engine, and do not continue driving until the cause is investigated. Driving with this light on can cause severe and irreversible engine damage within minutes.

Some newer cars use an electronic oil level sensor instead of a dipstick. On these vehicles, the oil level is displayed on the instrument cluster or infotainment screen through a vehicle information menu. Check your owner's manual for the correct procedure, and know how to access this display in your test car before your RSA driving test.

At minimum every two weeks and before any long journey. Check more frequently on older vehicles or cars known to use oil. Always check the oil level the day before your RSA driving test — not the morning of, so you have time to top up if needed.

Yes. The RSA examiner asks you to demonstrate technical checks at the start of the test, which includes showing the dipstick and filler cap locations and explaining how you would check and top up the oil. You must know where these are in your specific test car — practice with your ADI in the car you will test in.
More from the Vehicle Safety & Pre-Drive Checks series
Engine oil is checked in your very first EDT lesson.
BP Driving School covers the full under-bonnet check routine — oil, coolant, washer fluid — as part of EDT Session 1, exactly as the RSA requires. Book your EDT course — RSA-approved, Swords, North Dublin.

Already done EDT? Book a mock test to rehearse the full technical check sequence on test day.