Happy to share our experiences and preferences with decking oils as there are many on the market. There's water based and oil based. Different levels of gloss, colours, and everything in between.
For me, you can't go past Cutek Extreme. It's a top quality product and one I've used several times myself. I know some carpenters and a couple of building supplies companies that use/recommend it too. It gives a beautifully natural finish (without tinting), is long lasting and has the versatility of being tinted to your desired colour/tone. I've always found the timber I've applied it to is well preserved over the years.
I have always heard good things about Cabot's and Feast & Watson (which are available at Bunnings) too. - ProjectPete
We had around 80 sqm of decking installed, 60 out the back, 20 out the front. I used Cutek oil on the front deck, and Intergrain on the back. The Cutek soaks into the wood, the Intergrain product acts more like a sealant. Both are 1 year into their life, the Intergrain that isn't undercover has peeled and worn and that timber has cupped and split, the Intergrain undercover is fine. The Cutek that is both exposed to elements and undercover has greyed to a patina, but the wood is still in perfect condition.
Just about to embark on bringing the back deck to life, before using Cutek on it this time around. - Andrew8754
I have used Feast Watson Wet Look on the front and back steps, not exactly decking but still wood. - Brad
I tried Feast and Watson's Natural Decking Oil as I was hoping to let the timber shine as naturally as possible. I applied it onto new decking (Karri) and some on existing decking (unknown type and after some hectic sanding). Very happy with the results on both. Brought back both timbers to their natural glory. - Chaks_DIY
If you want to retain the natural colour of decking boards, your best bet is to use a clear finish. However, I wouldn't go doing it straight away. Most manufacturers recommend weathering the deck for at least 4 - 6 weeks before applying any oil. This allows the natural tannins and oils to seep out from the timber, and ensures an even finish.
It's also worth mentioning that if you want to ensure the longevity of your deck, you'll definitely need to repeat the clean/oil process every 6 - 12 months. Otherwise you'll end up with a grey deck and only a distant memory of the natural original colours. - Jackson
I have a spotted gum front deck and used Intergrain Natures Timber Oil - comes up a treat. I've just given mine a going over with Reviva before giving it another coat. Let it weather before coating, but you can also get around it by using a combo of Power Prep and Reviva - supposed to speed things along a little. - DIY_Dan