I wouldn't use RBO for a lotion unless you are going to use it up fast. You want oils with a longer shelf life. Regular coconut oil doesn't agree much with my skin, but MCT oil - a very close cousin to fractionated coconut oil - seems to be ok, and it doesn't go rancid fast at all
My three current favorites are jojoba, argan, and meadowfoam seed oil. Other nice oils are avocado, sweet almond, and apricot kernel; they are less pricey but also not as fantastic as the first three.
Grapeseed oil feels really nice on the skin, which is why it's often used as a massage oil, but I think it also has a short shelf life. Double-check me on though, as I'm not positive.
@AliOop RBO as in Rice Bran Oil - has a shelf life of about a year. Also, just so you know MCT is the same as fractionated coconut oil ☺
The majority of body lotion recipes I am finding call for jojoba oil. I have even seen some with MCT and sunflower oil.
The lotion I am making I am wanting to use for mature skin and was considering using rbo instead of jojoba. Just curious what others think and what they might or might not sub.
I recommend that you start by making smaller batches (100ml) and testing what oils you like.
Ask yourself what you are trying to achieve? If you are looking to say help dry cracked skin you would use different oils than you would if you are looking for something for oily skin. What part of the body are you using it on? What feel do you want it to have? Do you want it to be light? heavy? What type of skin do you have? How comedogenic is the oil? What's the shelf life? There are just a few things that need to be considered.
You may also like to consider what oils you do have on hand that you can use? Especially if you have are just starting out. It can be an expensive endeavour. There are a lot of different emollients on the market, each have their pros and cons; also not all suit all. Everyone's skin is different and we all like different skin feel. Some people like the moisturiser to sink into their skin immediately, some like when you can play with it a bit. It does take a bit of time to navigate the information out there and to find what you like.
All the information you have given us is you'd like it to be suitable for mature skin. There really isn't a "best" because as mentioned above it depends on your skin and what you want to achieve, what your skin can handle too.
You said you had RBO - I assume this is Rice Bran Oil?
Rice Bran Oil is a medium weight oil. It has a shelf life of about a year. I wouldn't use it on my face but it is one oil that gets used a lot in my formulas. It's a good sub in my opinion for sunflower oil. Ferulic acid that is in rice bran oil can help with aging and reduce age spots. It also can help with light and radiation damaged skin. Ferulic acid also helps prevent oxidisation and it can be more effective anti-oxidant than Vitamin E.
Jojoba is not actually an oil, it's a wax ester. It has this amazing ability as it mimics the sebum in our skin. It also penetrates the hair follicles but doesn't block the follicles. It basically mixes those things and kind of allows the skin to breathe. I know that's not a great description but I can't think of an easier way to say it. It is extremely popular because it is a stable emollient with a long shelf life (2 years).
You also mentioned
Fractionated Coconut MCT oil. It is popular in lotions again because of it's shelf life (2+years). It lasts longer than coconut oil. It's lightweight, doesn't have a smell, doesn't stain clothes. It is a favourite and highly used oil. There is no difference between MCT or fractionated coconut oil, it's just the different way they are marketed. MCT just means medium chain triglyceride, which is correct it is a medium chain triglyceride, it is actually caprylic/capric triglyceride. It basically gets called fractionated because it coconut oil that has been fractioned from a long chain triglyceride to a medium chain triglyceride. Both have the same INCI names ergo they are the same. FCO is sometimes marketed as oil free as it isn't a "real" oil like sunflower or olive oil, but it is still comedogenic. It's comedogenic rating is 2. It is kind a dry oil but deeply moisturising oil.
Sorry, I am trying to keep the post short but it's such a big topic.
You also mentioned
Sunflower Oil. It is low comedogenic, light oil so is good for face moisturisers. It is has some wonderful properties but it has a really short shelf life (3-6 months thereabouts). So unless you know you are going to use it within that time it's a great oil that is always recommended in beginner formulas, because it's cheap and if you stuff up, it's easy to replace. It's good for skin softening and it does have some anti-aging properties but because it has such short life it's one to use for experiments that you know you are going to use say within three months. It is also why, I would recommend starting with small batches. I personally wouldn't go smaller than 100g, you could go to 50g but you would have to ensure you have very accurate scale. As your preservative is usually around 0.5% - 1.0% and most scales for home use aren't great at the really tiny amounts.
Meadowfoam oil like jojoba is popular because it has a longer shelf life (2 years - maybe longer) and it is another popular emollient in anti-aging formulas. It is a light-ish, waxy kind of oil. It is resistant to oxidisation due to it's long chain fatty acids. It is often the oil that is recommended as a replacement for jojoba. Both have a comedogenic rating of 2 (some sources of meadowfoam I've seen have actually been lower at 1).
You might find this interesting if looking to sub jojoba for meadowfoam.
Comparison of Meadowfoam seed oil Vs Jojoba oil
I find it interesting that I can get jojoba in Australia a lot more easily and cheaper than meadowfoam, something that those in the Americas don't have an issue with as I believe it is native to Western Canada (& apparently Oregon). So, it is likely cheaper over there.
I could continue but I would most probably end up writing 2000 plus words. If you want some help with your formula, I will happily help. If you don't want to post your formula publicly that's okay. If you want me to help you please let me know. ☺