Our purchasing department want to change our oil supplier from Mobil to Houghton.
Some oils we use are Mobil DTE light, and Mobil DTE 24, both oils have a viscocity of 32 but the DTE light is a circulating oil and we use this oil on precision bearing spindles with a speed of 10000rpm and the DTE 24 we use for our smaller hydraulic tanks such as horizonral CNC lathes, on our larger units we use DTE 25.
Houghton wants to sell us Hydro HP 32 to replace both of these oils.
Can someone tell me if this is the right thing to do and if not why not.

If you are changing just due to costs then talk to your Mobil contact.
Some rationalisation could be done to improve your lubrication eg you could use DTE 24 in the DTE light applications. DTE 24 is one of the best hydraulic oils in the marketplace and provides cost benefits in terms of extended oil life and component life.

Try out Chevron Hydraulic Oil AW or Caltex Rando HD series oil with the viscosity grades you require.

All mentioned oils are good oils (although I cannot say the same for Houghton’s because I am not familiar with their oil, but that doesn’t mean they are not good oils), and whichever oil you end up with may serve you well. However, if you do change your oil, make sure new oil is compatible with what you have now, because, if incompatible, you are going to be up for a challenge to keep your operation smooth and trouble-free. The test is ASTM D7155-06, and if you don’t want lab to run the full test, as a minimum, request a Tier 1 part to be done.