Teak oils are not UV stabilized and rapidly oxidize and turn towards dark/black. Those old sailing ships werent painted BLACK, thats oxidized oil finishes!!!! The 'thin' oil coats that are applied to interior work quickly erodes in sunlight. An alternative to exterior teak oil is to 'resinate' the oil with upwards of 25% oil based varnish, apply several very *thick* coats ... will last 12-18 months before the inevitable 'darkening' ... BUT like 'straight' teak oil is very easily stripped with TSP. Once fully cured/dried resinated teak oil can be flat sanded and hand-rubbed with rottenstone & water to gain a gloss equalling a prime varnish job ... and still easily and quickly stripped with TSP later on. A good commercial source of resinated teak oil is "NuTeak" by "maryKate" (WORST Marine carries it).
Before I switched to the modern urethane/arcylic catalysed 2-part finishes, I did some experimentation by adding to the oil a bit of finely ground ferrous oxide powder (same stuff that probably is the UV component in alkyd-based Cetol, etc.) and found a life extension of 1 year ..... but HATED that orangey color, ... same intense HATRED I have for 'Cetol'.
I now use catalyzed acrylic/urethanes with catalyzed clear overcoats which can last 5+years with simple quick yearly maintenance: "Honey Teak" or "Smith & Co. 5 year clear". These are coatings from small suppliers so are available only directly from the manufacturer. They do not lift by water absorbption of the wood from the 'reverse' side of the wood. MUST be applied very thick with the base coats requiring care .... to be laid down 'thick'. I prefer 3 base coats + 2 clear coats for the initial application. They 'flow' best at cooler temps (45-55 degrees) and have immense fill quality needing only 220-100 grit sanding requirements (I just use purple scotchbrite pads) and since they are catalyzed you can apply coat over coat almost continuously. I use 'soft' artist brushes to apply ... no need for expensive 'badger'. You can do a total job in about 1+ to 2 days in 70 degree weather. They can be powerbuffed or hand-rubbed (rottenstone for super-gloss or pumice for satin) if you want to equal the quality of the 'very best' varnish jobs (with 1/10 the work). They are VERY expensive but when you amortize the cost over 5-6+ years they come out cheapest and least labor intensive. They do require a 'maintenance' coat of clear every year (just scrub with a 3M pad and 'slop on') or apply very thick overcoat every 2 years and very lightly powerbuff in the intervening year). I have a large 'teakey' and it takes me 8 hours to overcoat the clear topcoat everyother year. For new coatings they do start out with a orangy 'hue' that quickly (weeks) fades to amber similar to a tung oil based varnish. If/when you powerbuff be careful not to let the surface become hot when buffing or you will 'tear'/burn the surface .... just a light pressure from a 3M knobby foam pad with 3M "Perfect-it" using a high speed autobody shop polisher (set to LOW speed). Since these coatings contain easily buffed acrylic you might arrive at the super-gloss that you find on mega-yachts or private jet aircraft ---- "mirror-gloss" ..... ahhhhhhhh!, if you learn/develop that 'technique'. Definitely will make a Hinckley with a 'super-prime' varnish job blush with envy.
These coatings have a steep 'learning curve' for application - but in my mind are the most glossy/brilliant, absolutely longest lasting .... and cheapest overall.
If you flat sand (2000 or 3000 grit) and then hand-rub (rottenstone and water and BARE hand), you can develop the GLOWING irridescent patina of the surface wood cells .... like you do with a top-end prime varnish job.
= Honey teak. Should be applied ONLY to teak as their adherence to other species (Iroko, Ipe, etc.) is not 'good'.
For signature finish, you can order 'just' the amount of materials you want as they will 'split' the amount you want. Just tell them how many square feet of wood you are coating. Be sure to keep the catalyst in a refrigerator to keep it from 'kicking', and dont store in a boat refrig. as the constant 'rocking' of boat can make the catalyst 'kick'.
Just remember that the 'quality' varnish/coating jobs are 'worked hard' AFTER you apply them .... flatsanding then hand-rubbing (rottenstone, pumice etc., then powerbuffing, etc.) No one on this planet ever created a 'beautiful' finish coat directly from a 'can' ... .
FWIW .... The BEST interior varnishes are still 'hand made' ... for those I prefer HARD 'bar-top' varnishes made by an ancient paint shop proprietor (artist!!!!). Soft 'spar' varnish is for flexible spars; good interior varnish needs HARD varnish and the mass-production commercial folks simply dont make it anymore.
Hope this helps.