2. E-commerce platform query: Many e-commerce platforms, such as Taobao and JD.COM, keep product price information over the years. You can search the brand and model of diesel engine oil on these platforms to find the product prices over the years.
3. Consult the diesel engine oil distributor: If you know the distributor of diesel engine oil, you can contact him to consult the product prices over the years.
4. Inquire on industry consulting websites: Some industry consulting websites, such as the automobile industry consulting website, will publish diesel oil prices over the years. You can find relevant information by visiting these websites.