Diesel fuel is toxic to all plant material and will kill the weeds and grass it comes in contact with along with other plants it comes in contact with. Diesel will not kill the seeds making this a non-permanent solution. You will need to repeat this process continuously.Click to see full answer. Thereof, what kills grass and weeds permanently?But salt can do the job. Bring a solution of about 1 cup salt in 2 cups water to a boil. Pour directly on the weeds to kill them. Another equally effective method of how to kill weeds is to spread salt directly onto the weeds or unwanted grass that come up between patio bricks or blocks.Likewise, does petrol kill grass? If you want to permanently kill your grass and weeds, all you need to do is pour gasoline on it. Please don’t do this! Pouring gasoline into the soil affects the entire watershed, as well as all the plants and animals around the location. Gasoline is NOT something we should intentionally pour into our earth. Beside above, does gasoline kill grass and weeds? Using Gasoline to Kill Weeds A small amount of gasoline may be sprayed on weed foliage. Covering a yard with gasoline is not safe, but spot treating weeds is effective. Focus the spray on the leaves of the weed instead of the soil.Can you mix Roundup with diesel fuel?A small amount of diesel fuel with the roundup makes a good additive – surficant. Like, a gallon per 100 gallons of spray. The diesel will be more harmful o the environment that the roundup, but in small amounts the environment deals with the petrochemicals. A bit of nitrgen mixed in also helps with the roundup.