just use in car,no issues.

Use it. 7 months is not ideal, but doesn't have to be an issue. Since many of the volatile compounds will have evaporated off--leaving the breather open not as good as preventing temp swings--mixing with fresh fuel will help. I'd pour it into your car a bit at a time over the next few fill ups. 5L diluted into 50L won't matter much at all. Lawnmower good also. 

Give it a shake, pour some into a glass and let sit.
If there's water it will seperate.
Old gasoline with water has a smell, if your attuned to that.
Pouring as weed killer , not so green.

If hard starting , fuel getting old. It is this part of the aromatics that flash off thryu breathers , and perminate thru plastic container walls.
If an issue or think have, tip 1/2 out and fill with fresh. Do the same with 2nd 1/2 if doesnt fire up the lawn mower.

 A lot more is made of old fuel than really is.
 Stored classic cars (3 of 4 seasons plus) if concerned, owners leave a gallon or so in the tank , pour in a fresh 5 or 10L then head off the the gas station to top off.