Hi all What is the difference between synthetic and mineral oils. I am using delo 400 currently in petrol and diesel but have nearly run out. I recently got an e 140 cat digger and am wondering if a syn oil is usable as a hyd oil. Specs suggest delo 400 as a hyd oil for this machine but may try castrol 20w 50 as its only 2 bucks a litre over here at the moment.
Diesel engine and hydraulic oils have very different additive packages. I would not use engine oil in a modern hydraulic system unless it was my only choice. For example engine oils absorb moisture whereas most hyd oils let it settle, otherwise it increases the chances of cavitation and reduces the film strength. My understanding is that CAT lists engine oil as an option for situations where hydraulic oil can be very difficult to source. As far as conventional vs synthetic - synthetic can run at higher temps before oxidation occurs, viscosity is reduced at lower temps for less cavitation at start-up, and viscosity may be slightly increased at high temps. If the oil smells burnt or is running hot it might be worth it. ISZ