having trouble with staining Sleepers

Hi Everyone,
i just bought a house and started renovating in my spare time, i paved outside 60m2 and then built 900mm high garden beds around it with a 3m opening to the yard...

I used treated pine sleepers ( 200x50 ). all finsihed and lined the inside with plastic.. but i decided to stain them.. i am using Cabots decking oil with a merbu colour stain in it. ,,,

I gave it a coat... (looked good)

2days later ... ( looked faded)

3rd day,,,, ( Re - Coated )
4th day.... ( Re - Coated )

i have used 10L till now.... and am sort of about to give up... when it drys its looks really Dull,

Is there anything else i can use... i bought another 4L ( Cabots helpline said keep coating)

can i add a varnish to it or should i just grab the dpray gun and paint it?

anyone else had this problem before?

Most treated pine sleepers are CCA (Copper Chrome Arsenate) treated. They need to be completely dry before staining and I'd reckon they should be stained with stain not an oil with a stain in it.

I'm presuming that a merbau stain is on the red side and that being the case will be faded due to the fact that green kills red colour and the oil will be weakening it as it is drawn into the wood.

Just my thoughts. Never really had anything much to do with treated pine.