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IOCL recruits Grade A engineers through its own Computer-Based Test (from the 2025 cycle; earlier cycles used GATE score), followed by a GD/GT and a Personal Interview, with merit weighted 85:5:10.
Interview experience
IOCL interview experiences covering the written stage (IOCL CBT, or GATE in earlier cycles), Group Discussion / Group Task, Personal Interview, +1 more. Round-wise notes, common questions, and what candidates report clears each stage.
HR interview questions
IOCL HR interview questions with sample answer frameworks - motivation, relocation, STAR stories, and culture-fit prompts.
| Round | Duration | What it tests |
|---|---|---|
| Computer-Based Test (Grade A, 2025 cycle onward) | 150 min, 100 questions | 50 aptitude/reasoning/English + 50 domain; 85% of merit |
| GATE score shortlisting (cycles up to 2024) | - | GATE score in the matching discipline, replaced by the CBT from 2025 |
| Group Discussion / Group Task | 15-20 min per group | Communication, teamwork, leadership, clarity of thought |
| Personal Interview | 15-20 min | Technical depth, behavioral traits, role suitability |
| Document Verification & Medical Test | - | Eligibility documents, category certificates, physical fitness |
These answers come from summaries of IOCL’s 2025 and 2026 Grade A advertisements. The advertisement for your cycle on iocl.com is the final word.
| Question | Answer |
|---|---|
| Is GATE required? | No, not since the 2025 cycle. IOCL now runs its own CBT for Grade A Graduate Engineers; earlier cycles shortlisted on GATE score. |
| How many questions and how long? | 100 one-mark questions in 150 minutes: Section A general aptitude (20 quantitative, 15 reasoning, 15 English) in 60 minutes and Section B domain knowledge (50 questions) in 90 minutes. |
| Does it have negative marking? | Yes. 0.25 marks are deducted for each wrong answer; unattempted questions carry no penalty. |
| Is there a sectional cutoff? | Yes. UR, EWS and OBC candidates need 40% in each section and 45% overall; SC/ST need 35% and 40%; PwBD 25% and 30%. |
| How much is the cutoff? | The qualifying marks above are the floor. The actual shortlist cutoff is not published; IOCL shows it only in candidate logins. |
| What happens after the CBT? | GD and Group Task (5% of merit) and a Personal Interview (10%), each with a 40% qualifying mark. The CBT carries 85%. |
| Is there a service bond? | Yes. Summaries of the 2026 advertisement list Rs 3 lakh for Grade A (Rs 50,000 for reserved categories). |
| Which disciplines? | The 2026 advertisement covered Civil, Chemical, Electrical, Electronics and Communication, Mechanical, Instrumentation and CS/IT at Grade A. |
The Personal Interview follows your discipline with a refinery, pipeline or marketing slant. These are topics candidates report on Glassdoor and in LinkedIn and YourPedia write-ups; they show the level, not a fixed list.
| Branch | Reported questions and topics |
|---|---|
| Chemical | Heat transfer, mass transfer and fluid mechanics fundamentals. Crude distillation and FCC basics. Your project and internship in depth. |
| Mechanical | Tanks and storage systems. Pumps, NPSH and cavitation. Heat exchangers and basic machine design. |
| Electrical | Power factor and its correction, induction motor starting, transformers and plant power distribution. |
| Instrumentation | PID control loops, control valves and P&ID reading, plant safety interlocks. |
| CSE / IT | Enterprise IT and analytics use in a refinery or marketing network, plus your project and DBMS and networking basics. |
Asked across every branch: tell me about yourself and your family, why IOCL and why a PSU, your final-year project and internship, and whether you accept a refinery or remote posting.
In cycles up to 2024, IOCL shortlisted Engineer/Officer candidates on GATE score in the relevant discipline before GD/GT and the interview. From the 2025 cycle the Grade A engineer advertisement replaced GATE with IOCL’s own CBT, so check which route your advertisement uses.
Common questions
IOCL’s own Computer-Based Test is now the written filter for Grade A Graduate Engineers: 100 objective questions in 150 minutes, split between general aptitude, reasoning and English (50) and domain knowledge (50), with 0.25 negative marking and sectional plus overall qualifying marks by category. Other entries, such as Diploma Engineers (Grade E0), sit the same style of CBT.
Common questions
Run for both entry routes after shortlisting, the GD/GT evaluates how clearly you communicate, whether you build on others’ points, and how you perform under a time-boxed group setting.
Common questions
The closing technical-and-fit stage, going deep on your engineering discipline as it applies to refinery, pipeline, or plant operations, plus your final-year project and motivation for a PSU career. Candidate reports (LinkedIn, YourPedia) often describe 60% technical / 40% HR split for core branches - CSE panels add enterprise IT, analytics, and IoT mapping questions.
Common questions
Sample answer frameworks are on the IOCL HR interview questions page.
IOCL’s written filter depends on the cycle and the post. Up to 2024, Engineer/Officer roles used GATE score as the technical filter. From the 2025 cycle, Grade A engineers sit IOCL’s own 100-question CBT, with sectional and overall qualifying marks by category - clearing them only earns a GD/GT and interview shortlist, not an automatic call. This page covers the Grade A Graduate Engineer route. Diploma Engineer (E0) and other posts are advertised alongside it with their own grade, pay and bond, and apprentices are engaged under a separate apprenticeship scheme. Read your own advertisement before deciding whether to prioritise GATE prep or CBT-style aptitude and domain practice.
Public summaries of IOCL’s Engineer/Officer Grade A advertisement (for example CareerPower’s breakdown of the official notification) describe composite selection roughly as:
| Component | Typical weight | Notes |
|---|---|---|
| CBT | 85% | 100 MCQs, +1/−0.25, 150 minutes; 50 domain + aptitude/reasoning/English |
| GD & GT | 5% | Often 40% minimum qualifying marks on the combined GD/GT stage |
| Personal Interview | 10% | Often 40% minimum qualifying marks |
GATE-based cycles reported by candidates sometimes cite similar 85 / 5 / 10 splits but use GATE score instead of CBT - always read your notification for the year and post code.
The crude distillation unit separates crude oil into fractions by boiling point. Crude is preheated in a train of heat exchangers, desalted, then fired in a furnace to roughly 350 to 370 degrees Celsius and flashed into an atmospheric column, where vapour rises through trays and progressively condenses. Light ends and naphtha leave the top, kerosene and diesel are drawn as side streams, and the un-vaporised residue leaves the bottom. That residue goes to a vacuum distillation unit, where reduced pressure lowers the effective boiling points so heavier gas oils can be recovered without thermally cracking the material. It is first because every downstream unit - reformer, hydrotreater, FCC - is designed for a specific boiling range, so the crude must be cut into those ranges before anything else can process it.
FCC breaks heavy, long-chain vacuum gas oil molecules into lighter ones using a fine zeolite catalyst fluidised in the feed at roughly 500 to 550 degrees Celsius. It exists because the natural yield pattern of crude does not match market demand: crude produces far more heavy fraction than the market wants and far less petrol than it wants, so FCC upgrades low-value heavy oil into high-value gasoline and LPG. The unit runs as a coupled pair - the riser reactor where cracking happens and the regenerator where coke deposited on the catalyst is burnt off - and that combustion supplies the heat the endothermic cracking reaction needs, which is why the two vessels are described as being in heat balance. Catalyst circulates continuously between them.
NPSH available is the absolute pressure head at the pump suction minus the vapour pressure of the liquid at pumping temperature, expressed in metres of liquid. NPSH required is the value the pump manufacturer specifies for that impeller. Cavitation occurs when NPSH available falls below NPSH required: the local pressure at the impeller eye drops below the liquid’s vapour pressure, vapour bubbles form, and they collapse violently as pressure recovers downstream - pitting the impeller, causing a gravelly noise, and reducing head and flow. The practical fixes are to raise suction pressure by increasing the liquid level or elevating the tank, to reduce suction line losses by shortening the line or increasing its diameter, or to lower the pumping temperature. This is one of the most commonly asked IOCL interview questions for mechanical and chemical candidates, because pumps are everywhere in a refinery.
Reynolds number is the dimensionless ratio of inertial to viscous forces, calculated as density times velocity times pipe diameter divided by dynamic viscosity. For flow in a circular pipe, roughly below 2000 the flow is laminar with an orderly parabolic velocity profile, above about 4000 it is turbulent with chaotic mixing and a flatter profile, and between them lies a transition region. It matters for pipeline design because the friction factor - and therefore the pressure drop and the pumping power you must pay for - is calculated differently in each regime: in laminar flow the friction factor is simply 64 divided by Reynolds number, while in turbulent flow it depends on both Reynolds number and relative pipe roughness via the Colebrook equation or the Moody chart. Turbulent flow also gives much better heat transfer, which is why exchanger tubes are deliberately sized for it.
In counter-current flow the two streams enter at opposite ends, so the temperature difference between them stays relatively uniform along the whole length, and the log mean temperature difference is higher than for co-current flow with the same terminal temperatures. Since the duty is the overall heat transfer coefficient times the area times the LMTD, a higher LMTD means less area is needed for the same duty - a direct capital saving. Counter-current also allows the cold stream outlet to exceed the hot stream outlet temperature, which is thermodynamically impossible in co-current flow where the two streams can at best approach each other. Refineries chain these into a crude preheat train precisely to recover as much heat as possible from hot product streams before firing the furnace, which is where the fuel cost sits.
Power factor is the ratio of real power in kilowatts to apparent power in kilovolt-amperes, equal to the cosine of the phase angle between voltage and current. Induction motors, which dominate a refinery’s load, draw lagging reactive current for magnetising, which pulls the power factor down. A poor power factor means higher current for the same useful work, so cable and transformer losses rise with the square of the current, voltage drop worsens, and utilities levy a penalty tariff. Correction is normally done with capacitor banks connected in parallel, sized to supply the reactive power locally instead of drawing it from the grid, and often switched automatically by an APFC panel as load varies. Over-correction into a leading power factor is undesirable too, since it causes voltage rise and can resonate with system harmonics.
A PID controller compares the measured process variable to the setpoint and computes an output from three terms. The proportional term reacts to the present error and gives fast response but leaves a steady-state offset. The integral term accumulates past error and drives that offset to zero, at the cost of adding phase lag and risking integral windup if the valve saturates. The derivative term responds to the rate of change of error, adding damping and anticipating overshoot, but it amplifies measurement noise so it is often omitted on flow loops. In practice, fast and noisy loops such as flow and pressure are tuned as PI, while slow loops such as temperature benefit from adding D. Tuning is done by methods like Ziegler-Nichols or, more commonly in a running plant, careful incremental adjustment while watching the trend.
A pressure safety valve is the last mechanical line of defence against overpressure: it is a spring-loaded device set to lift at a defined pressure, relieving the excess so the vessel never exceeds its design pressure, and it reseats once pressure falls. It is sized for a credible worst-case scenario such as blocked outlet, external fire, or thermal expansion of trapped liquid, and it is deliberately independent of the control system so a failure of instrumentation cannot disable it. The relieved hydrocarbon cannot simply be vented, so it is routed through a closed relief header to a knockout drum that removes liquid, and then to a flare stack where it is burnt with steam injection for smokeless combustion. The pilot flame and a continuous purge gas flow are what prevent air ingress and flashback into the header, which is the safety detail interviewers usually probe.
A Process Flow Diagram shows major equipment, streams, and energy flows at block level - enough to understand chemistry and mass balance. A Piping and Instrumentation Diagram adds line sizes, valves, instruments, control loops, and safety devices operators and construction teams need. Interviewers ask this to see whether you think like a plant engineer, not only a textbook student.
Downstream covers refining, processing, marketing, and distribution of petroleum products closer to the customer. Upstream (ONGC’s core) is exploration and production of crude oil and gas. IOCL integrates large refining capacity, pipelines, and retail fuel networks - that downstream focus drives interview questions on process units, product quality, and logistics rather than drilling rigs.
Hydrotreaters remove sulphur, nitrogen, and metals from naphtha, diesel, or kerosene streams by reacting them with hydrogen over catalysts at high temperature and pressure. Environmental regulations on sulphur in transport fuels make hydrotreating essential before blending or further processing. It connects interview answers on desulphurisation to real IOCL product specs.
Ensure personal and team safety: raise alarm, eliminate ignition sources, evacuate non-essential personnel, and notify control room/shift in charge per plant procedure - do not attempt heroics alone. Isolate the source if trained and if safe. IOCL panels use scenarios like this to test process safety culture, not trivia recall.
Structure a short opening stance, cite one factual anchor (India’s net-zero timeline, IOCL biofuel or hydrogen initiatives from public reports), invite others’ views, and summarise a practical conclusion. Evaluators reward listening and synthesis over shouting; many reports describe groups asked to reach a unanimous conclusion.
Yes - 0.25 marks are deducted for each wrong answer and unattempted questions carry no penalty. The paper has 100 one-mark questions in 150 minutes: 50 general aptitude (20 quantitative, 15 reasoning, 15 English, 60 minutes) and 50 domain questions (90 minutes).
GATE is not used for Grade A engineers from the 2025 cycle; IOCL runs its own CBT. The published minimum is 40% in each CBT section and 45% overall for UR, EWS and OBC (35% and 40% for SC/ST), plus 40% in GD/GT and in the interview. The actual shortlist cutoff is higher and is shown only in candidate logins.
IOCL’s Grade A engineer process has 3 scored stages: IOCL’s own Computer-Based Test (85% of merit), a Group Discussion and Group Task (5%) and a Personal Interview (10%), followed by document verification and a medical test. Cycles up to 2024 shortlisted on GATE score instead of the CBT; from the 2025 cycle IOCL runs its own CBT.
No - from the 2025 cycle IOCL recruits Grade A engineers through its own Computer-Based Test, not GATE. Earlier Engineer/Officer cycles shortlisted on GATE score. The CBT covers general aptitude (quantitative, reasoning, English) and your engineering domain, with sectional and overall qualifying marks by category.
The Personal Interview focuses on your core engineering discipline (chemical, mechanical, electrical, civil, or instrumentation fundamentals depending on your branch), how that knowledge applies to refinery, pipeline, or plant operations, your final-year project, and behavioral/motivational questions about why you want a PSU career. The GD/GT round evaluates communication, teamwork, and clarity of thought on a given topic or task.
Three scored rounds: the CBT, a combined GD/GT, and a Personal Interview, followed by document verification and a medical fitness test. In cycles up to 2024 the GATE score took the place of the CBT. There’s no separate online coding assessment like at private-sector companies.
Put most of your time into the CBT, since it carries 85% of final merit: your GATE-level domain syllabus for Section B and aptitude, reasoning and English for Section A, each of which has its own qualifying mark. For both, revise core subject fundamentals relevant to refining, pipelines, or plant engineering, prepare a clear reason for wanting a PSU/public-sector career, and practice structured, concise speaking for the GD round.
It has 100 objective questions in 150 minutes: Section A is general aptitude (20 quantitative, 15 logical reasoning, 15 English, 60 minutes) and Section B is 50 domain questions (90 minutes), with 0.25 negative marking. Clearing the sectional and overall qualifying marks only makes you eligible for the GD/GT and interview shortlist - it doesn’t guarantee a call on its own.
Use this as a default four-week loop before a IOCL drive. Adjust to your invite timeline.
10-day crash version: Days 1-4 timed DSA, days 5-7 resume projects + CS fundamentals, days 8-9 mock interviews out loud, day 10 HR STAR stories on the HR page.
Candidate-reported fresher/early-career packages for IOCL often cite ~₹12-17 LPA CTC chatter; Grade A basic ₹50,000. Treat forum numbers as ranges, not guarantees - confirm the written offer letter for your team and location.
Good fit: You will put months into GATE or a domain CBT, you can speak plant or marketing basics without Wikipedia fluff, and you accept posting flexibility across refineries, pipelines, or marketing locations named in the advertisement.
Harder path: You only practised LeetCode; you recite CMD names and refinery lists you cannot explain; you treat GD/GT as optional; you refuse every plant city while ticking “anywhere.”
Interview process details and sample questions on this site are editorially organized from public candidate reports and hiring write-ups, with round structure, prep notes, and company-specific framing added by our team. For round-by-round stories, see the IOCL interview experience page. For OA papers and coding drills, use IOCL on placementpapers.app. CBT quick answers and branch-wise topics draw on CareerPower’s breakdowns of IOCL’s 2025 and 2026 engineer notifications, Physics Wallah’s IOCL Grade A result page, and Glassdoor candidate reviews for Indian Oil.
