Looking for a cheap way to get a greener lawn? A surprising tip from the LAWN LIFE YouTube channel suggests raiding the automotive aisle – or even your local gas station pump. Host Jesse recently explored using Diesel Exhaust Fluid (DEF), the stuff modern diesel trucks need to cut emissions, as a lawn fertilizer and shared results that might make homeowners do a double-take.The secret, Jesse explained in his video, is that DEF is mostly just deionized water and urea. Urea is a common, powerful nitrogen fertilizer known for giving lawns a quick green boost. While plain granular urea is still the cheapest nitrogen overall, Jesse noted that when it comes to liquid options, DEF “is by far the cheapest fertilizer you can buy in liquid form.”He even showed viewers that “…you can get fertilizer at the freaking pump… just wild,” pointing out its low cost at commercial truck stops compared to traditional bottled fertilizers. After doing the math, Jesse determined DEF effectively works out to a “15-0-0 fertilizer at 15 percent nitrogen.”Jesse then demonstrated how to apply it using a backpack sprayer, warning lawn-care DIYers not to go over “0.2 pounds of nitrogen per thousand square feet” to avoid burning the grass. He stressed the importance of calibrating sprayers first for anyone new to the technique.

So, did it work? Jesse tested DEF on a neglected section of his lawn. He reported “pretty dang good” results came after about eight days and two applications, explaining that the first attempt was likely hampered by windy conditions.

His final take: Jesse concluded that “DEF would be a great product to spoon-feed your lawn every one or two weeks in the summer” if you’re looking for frequent, light nitrogen boosts.Using diesel truck fluid as a substitute lawn fertilizer definitely sounds weird, maybe even a bit shocking. However, as the LAWN LIFE video showed, urea in DEF is a straightforward nitrogen source. This makes it an unexpectedly cheap and effective option if your lawn needs a quick green-up and a boost for healthy growth, provided you mix and apply it carefully.

Of course, using DEF as a lawn fertilizer goes against every warning on the box along with the manufacturer’s recommended usage. We’d never recommend using a product off-label. But, hypothetically, if you did… let us know how it works!