Teak oils ....
There are many and various forms of teak oil. Teak oil can be applied in such a way that it is thicker and glossier than VARNISH. The ultimate downside with all teak oils is that they continually oxidize and eventually turn 'dark'; and, if you leave them on long enough will turn black .... thats not black paint on those old sailing ships, its oil. When exposed to the sun oil will eventually over the years turn BLACK, oil over teak in a boats interior will eventually over the years darken and the interior will end up looking like the inside of a tomb. Just like most coatings, teak oil should be applied thick and heavy. Those that simply "lay-on and wipe off" usually are frustrated with a short 'service life' of the oil. If you want long lasting oil finish, lay it on but dont wipe it off. (Caution, Linseed based oil doesnt cure to a hard finish but remains 'sticky' for a long time.) The good news with oil is that it is easily removed by soaking the old oil finish with TSP trisodium phosphate... but the wood also ages underneath and usually needs to be bleached (oxalic acid) to bring back color and 'hue'. To gain a high gloss oil finish: apply MANY thick coats of oil, letting each coat dry and 'cure'. Typically 5-10 thick coats are needed. Then FLAT sand the next to final coat and carefully apply the final coat and let cure for about one month. Then flatten the surface with 600 wet and dry paper and then use rottenstone and water (just a few drops of water to make a thin paste) and hand-rub until the surface looks like glass. You can expedite the 'fill' by mixing up to 25% oil-based varnish into the oil OR you can buy 'resinated' teak oil .... "NuTeak" by MaryKate, etc. Resinated oil can be hand-rubbed and power-buffed to a MOST brilliant shine/gloss. Again, the 'good' thing about oils is that they are *easily* 'stripped' with TSP. The downside is that oils in exterior service usually have to be stripped every two years. Gelcoat is chemically compatible with TSP. There are many 'modern' coating that remove the 'hassle' of both oil finishes and varnish ....Bristol Finish, Smith & Co. "5 year clear", Honey Teak, etc. All look like prime varnish and are loooon lasting .... able to hand-rubbed and/or power-buffed too. In ALL finishes its the 'finish' work of flat sanding then polishing that make the distinct difference. There is NO finish that you can just 'slop on', although prime varnish has the best 'flow-out' and least need to be 'polished'. For exterior teak my preference is to simply 'seal' it with a mix of SEMCO & Teak Wonder - longer lasting and better looking than 'oil' ..... OR apply one of the very long lasting 'moderns'. hope this helps.