What is the formula of automotive urea solution?

[VonAshley]

Automotive urea solution formula is as follows: high-purity urea 32.5%, deionized water 52.5%, methanol 15%. Below is the relevant introduction of automotive urea solution: 1. Working principle: To make trucks meet the National IV emission standards, the SCR system (Selective Catalytic Reduction technology) must be used in exhaust treatment. This system requires urea solution to treat nitrogen oxides in the exhaust, making urea a necessity. 2. Raw materials: Urea refers to a urea aqueous solution with a urea concentration of 32.5% and the solvent being ultra-pure water. The raw materials are special automotive urea raw materials and ultra-pure water. Urea is mainly obtained from the purification of industrial urea, and automotive urea must use electronic-grade ultra-pure water.

[AdalineFitz]

Back when I worked at the auto repair shop, I came across many cases involving urea solution. The standard formula is actually just two things: 32.5% high-purity automotive-grade urea plus 67.5% ultra-pure deionized water. Don't underestimate this ratio—a concentration deviation of over 1% will render the exhaust treatment ineffective. If the concentration is too low, nitrogen oxides won't be properly treated; if it's too high, it's prone to freezing and clogging the pipes. The most critical requirement is the purity of the water—even regular mineral water won't do; conductive impurities must be completely removed. Once, a car owner tried to save money by buying bulk solution, and the nozzle ended up completely crystallized and clogged. The labor cost for cleaning alone was enough to buy ten barrels of proper product. Remember to choose products with ISO22241 certification printed on the packaging, preferably with a freezing point below -11°C.

[Silas]

Having driven trucks for over a decade, I've used at least several hundred liters of urea solution. While its formula appears simple, it's actually quite particular. The core is a 32.5% urea mixture with ultra-pure deionized water, but roadside vendors often cut corners. Water with excessive impurities can corrode the silver-plated nozzle coating, triggering fault codes every few days. The most critical factor is biuret content—inferior products start crystallizing at just 60°C. I've seen exhaust pipes completely clogged with white deposits. DIY mixing is even less reliable—ordinary distilled water with 300μS/cm conductivity exceeds standards. You need medical-grade pure water below 0.1μS/cm, and the mixing temperature must stay constant at 25°C. Now I only use API-certified barrel solutions—the transparent bottles let you verify there are no suspended particles.