Your questions about hair oil answeredWhat is the best hair oil?After months of testing across our straight, curly and coily hair types, we concluded that Olaplex’s no.7 bonding oil was the best hair oil, thanks to its frizz-smoothing, shine-boosting and damage-softening abilities. Dyson’s omega hydrating hair oil also seriously impressed us, particularly on Aidan’s curls, thanks to its featherlight but nourishing finish. Meanwhile K18’s molecular repair oil stood out after I saw my damaged lengths begin to look healthier after repeat use. And lastly, for a more affordable option, L’Oreal Paris’s elvive extraordinary oil punched well above its price point.How we tested hair oilsHair oils are deeply personal and what works beautifully on coarser strands can easily overwhelm fine hair types. To properly put a variety of formulas through their paces, I called on two expert testers with type 3 and 4 hair textures to join my own type 1C/2A strands. Together, we used the oils through numerous wash days, in-between wash days, styling sessions and workouts to assess how the formulas performed in normal life. Specifically, we considered the following criteria: Weight: We noted how heavy or lightweight each oil felt on our different hair types, and whether it caused our strands to look greasy, limp or stringy. Shine: We assessed whether the oils gave our hair a healthy gloss or a slick, unsightly finish. Nourishment: We looked at how effectively each formula softened dryness, smoothed split ends and improved manageability. Frizz control: We monitored how well the oils tamed flyaways and held up in humidity, wind and during/after a workout. Curl and coil compatibility: On textured hair, we considered how the oils affected definition, bounce and moisture retention. Longevity: We tracked how hair looked and felt after washing and in the days after, paying attention to greasiness, dryness and overall shape retention. Texture and application: We considered dispenser design, how easily the oils spread through the hair and whether the formulas layered well with other styling products. Value for money: We factored in bottle size, how much product was needed per use and, ultimately, whether the performance justified the price. What hair oil should I use for my hair type“I recommend oils based on things like hair thickness, porosity, dryness or whether someone has loose fine curls versus thick, dense coils,” reveals Dublin.Expanding on this, she tells me, “On looser curls, I go for something really lightweight, like an argan oil or anything with that soft slip. It gives shine without dragging the curl down.“For medium textures, things like coconut or rosemary oils give a good dose of nourishment but still feel wearable. They add moisture without making the hair feel coated.“Thick, coarse or very curly hair usually drinks up richer oils. Castor oil or a blend with heavier ingredients (like a mask) tend to smooth, hydrate and really bring out the curl definition.”Is argan oil good for hair?“Argan is packed with vitamins and healthy fats, so it softens the hair, calms flyaways and gives a nice sheen without weighing anything down,” reveals Dublin. Personally, she explains “[she’ll] use it as a pre-treatment on the scalp, leave it on for 10-15 minutes before washing, especially on clients with really dry scalps.”Meanwhile, if styling the hair, she recommends “rubbing a small amount between the palms and targeting the drier areas, then finishing with a tiny bit on the ends.”Is coconut oil good for hair?“I personally don’t use coconut oil on my clients because I find it can actually be drying,” warns Dublin. It can work for some medium textures however, so it’s worth experimenting to see if it suits your hair type. Is castor oil good for hair?“Castor is heavier, but it’s great for coating all the hair and really hydrating the scalp before braiding,” touts Dublin. As for how to use it, she suggests: “After a wash, put a small amount on before braiding as a treatment. It helps lock moisture in and keeps the scalp happy.”Is rosemary oil good for hair growth?“Rosemary mixed with a bit of peppermint works really well for dry scalps and can support hair growth,” confirms Dublin. In her experience, “It leaves the scalp feeling fresh and clean, almost like a face mask, but for your roots. It’s great for resetting the scalp without adding heaviness.”Why you can trust IndyBest reviewsAs a senior shopping writer, Lucy Smith is frequently testing the latest in haircare, and often speaks to trichologists and stylists to inform her reviews. For instance, she’s covered the best leave-in conditioners, the best shampoos and conditioners and compiled an expert guide to choosing the best leave-in conditioners.Alongside writing about beauty for IndyBest, Ateh Jewel is herself a beauty brand founder. She lent a hand to the team’s review of the best beauty advent calendars last year and, recently contributed to a new round-up of the best foundations. She’s often speaking about afro hair and proper coil care, and was the perfect person to test hair oils from a type 4 texture perspective. Aidan Milan has plenty of experience in the field of haircare and has covered numerous products for curly hair from the likes of Cantu, Colour Wow and more. With her own head of seriously healthy curls, she was well placed to put all manner of hair oils through their paces. Read more: 14 best anti-frizz products, tested