Mustard Oil vs Groundnut Oil — Which Suits South Indian Cooking?

Anyone who grew up south of the Vindhyas knows the answer to this question before they ask it. Groundnut oil is for cooking. Mustard oil is for pickling, occasionally for a Bengali friend's macher jhol, and your grandmother might still use it on your hair during winter. But it does not belong in the dabba where the daily oil is kept.

That, at least, was true forty years ago. Today the answer is a little more complicated.

Geography used to decide what you cooked with

For most of the twentieth century, the cooking oil in your kitchen was decided by whatever grew within a 200-kilometre radius. Bengal and the east pressed mustard. Punjab and Haryana also pressed mustard, plus some til. The Konkan coast pressed coconut. Tamil Nadu, Karnataka, Andhra, and the Deccan plateau — wherever red soil met a long dry season — pressed groundnut.

Modern transport changed all this. Sunflower from a Telangana mill could reach a Chennai kitchen within a week, refined and bottled. By the 1990s, regional preference began to flatten. By 2010, the average urban Indian household simply kept whatever oil was on the supermarket shelf that month.

The interesting development, in the last six or seven years, is that people have started reaching back. Not for nostalgia. For flavour, and increasingly for nutrition. If you want to understand why the same oil can cost ₹150 a litre refined and ₹600 a litre cold-pressed, we've written a separate piece on that — see Wood-Pressed, Cold-Pressed, Refined — What These Words Actually Mean.

What the two oils actually taste like

A cold-pressed groundnut oil — the kind that comes out of a slow-turning wooden press — smells almost identically like the peanuts that went in. When you pour it into a hot pan, the smell deepens but the character doesn't change. This is its great virtue. It carries no flavour of its own that competes with what you are cooking. Spices land cleanly. Curry leaves crackle in it without losing their citrus note. A tomato gravy made in groundnut oil tastes of tomato.

A cold-pressed black mustard oil is the opposite. You can smell the bottle from across the kitchen. The pungency comes from a compound called allyl isothiocyanate — the same family of compounds that make wasabi sharp. Refined mustard oil has these compounds heated out, which is also why most supermarket "mustard oil" is essentially just yellow cooking oil with a faint mustard label. The cold-pressed black variety is the real thing.

Yellow mustard oil, which we also press, sits in between. Milder, still aromatic, still recognisably mustard, but without the eye-watering kick. People moving to mustard oil for the first time often start here.

What each oil is actually for

Groundnut oil is the workhorse of South Indian cooking and the reason should be obvious. It has a high smoke point — somewhere around 220°C even unrefined — which makes it suitable for tadka, deep frying, sautéing, and everything in between. It's also stable enough to be reheated once without breaking down, though we wouldn't push it to two or three rounds.

In Tamil and Telugu kitchens, groundnut oil is what goes into the dosa pan, what tempers the sambar, what fries the murukku for Diwali. It pairs particularly well with the dry-roasted spice profile of the South — pepper, mustard seed, asafoetida, curry leaf, urad dal. The fat profile is heart-friendly when the oil is unrefined: mostly monounsaturated, with a useful share of vitamin E retained.

Mustard oil's place is more specific. It is the traditional oil for Indian pickling, and for good reason. Its antimicrobial compounds genuinely help preserve. Almost every classical Indian achar recipe specifies mustard oil, and substituting groundnut oil for the pickling step produces a pickle that will not keep nearly as long. Beyond pickling, mustard oil belongs in dishes that can carry its flavour — Bengali shorshe ilish, Bihari potato bhujia, Rajasthani laal maas, the mustard-greens saag that Punjab does well.

For routine sabzi or daily dal tadka in a South Indian kitchen, mustard oil is generally overkill. The flavour fights the food. In a Tamil kitchen, where rasam wants its sourness and pepper to be clean, mustard oil would muddle it.

If you want a third option that is even more neutral than groundnut — for baking, for delicate dishes, for households that prefer milder oil — cold-pressed sunflower oil is the defensible choice. For finishing drizzles and Ayurvedic body care, cold-pressed black sesame oil brings a deep nutty character that neither groundnut nor sunflower can replicate.

A note on health, briefly

The health debate around mustard oil deserves a paragraph. For years, the FDA and EU classified it as "for external use only" because of its erucic acid content. Indian regulators have always disagreed, and recent studies have pushed back on the erucic-acid panic — the levels in cold-pressed mustard oil, consumed in quantities Indian households actually consume, don't appear to be a meaningful cardiovascular risk. The FSSAI has not moved off its position that mustard oil is edible.

Groundnut oil's omega-6 content is sometimes flagged in modern "seed oil" discussions. The argument is overstated, in our view. Cold-pressed groundnut oil consumed alongside a varied diet is not the problem. Refined seed oils used in industrial fried food are.

For most home cooks, the more important variable than fatty-acid profile is how the oil was made. A cold-pressed oil retains its natural antioxidants and vitamin E. A refined oil has been bleached, deodorised, and stripped down to a neutral cooking medium. The difference shows up in flavour, in shelf life, and probably — though the science is still settling — in long-term nutrition. See our full FAQ on oils for more on this.

Which to keep in the kitchen

If your cooking is predominantly South Indian — daily, weekly, what the household eats — your default should be cold-pressed groundnut oil. For pickling, hair oil, or the occasional Bengali or Bihari dish, keep a smaller bottle of cold-pressed black mustard oil alongside.

If you do a lot of light cooking and want something even more neutral than groundnut, cold-pressed sunflower is a defensible third bottle. Two oils are usually enough for a working kitchen, though.

The wrong answer is to use a single refined "blended" oil for everything, which is what supermarket convenience has pushed most urban households toward. The right answer is to match the oil to the dish, which is exactly what your grandmother was doing.

Related reading

• Wood-Pressed, Cold-Pressed, Refined — What These Words Actually Mean
• How Your Cooking Oil Is Really Made — and Why the Method Matters
• Shop all cold-pressed edible oils

Frequently asked questions

Is mustard oil safe for everyday cooking in India?

Yes. FSSAI regulates mustard oil as edible and has done so for decades. The concerns over erucic acid that led to bans in the US and EU don't translate directly to Indian usage patterns or to cold-pressed Indian mustard oil specifically. That said, mustard oil is best used for dishes that can carry its flavour — not as a daily default for every preparation.

Can I use groundnut oil for deep frying?

Yes. Cold-pressed groundnut oil has a high smoke point and a stable fatty-acid profile that handles deep frying well. Avoid reheating the same oil more than once, and don't keep it standing in the kadai for repeated rounds across days. A fresh batch for each frying session is the right approach.

Why is cold-pressed groundnut oil more expensive than refined groundnut oil?

Cold pressing yields less oil per kilogram of peanut than chemical extraction. A wooden press extracts roughly 30% of the available oil; solvent extraction using hexane gets close to 95%. The cost difference reflects that yield gap, plus the slower process, plus the lack of bleaching and refining. You are paying for retained nutrients, flavour, and the absence of chemical processing.

Which oil should I use for pickling?

Cold-pressed black mustard oil, almost without exception. The mustard compounds act as natural preservatives and the strong flavour is what classic Indian pickle recipes are built around. Yellow mustard oil works for milder pickles. Groundnut oil is not a good pickling oil — pickles made with it spoil noticeably faster.

Is the strong smell of mustard oil a sign of quality or a problem?

Quality. The pungency of cold-pressed black mustard oil comes from naturally occurring allyl isothiocyanate, which is destroyed by heat refining. If your mustard oil has a faint or neutral smell, it has been refined and the characteristic compounds have been removed. The eye-watering kick is the marker of authenticity.