My D-6 has a Be Ge pump on it. It had hydraulic oil in it but I’ve been told it requires SAE 30 motor oil. It’s a La Plante Choate hydraulic system. The hydraulic tank does state to use motor oil. Do I use hydraulic oil or motor oil? 

Use 30wt. motor oil. You should get enough responses to this. The motor oil costs a little more but the better quality is well worth it.
Craig

In my situation, I use implements with both newer tractors that use hydraulic oil and older Cats with Be-Ge pumps,  I put hydraulic oil in the Be-Ge pumps instead of SAE 30 to avoid cross contamination, and the Be-Ge pumps work fine with hydraulic oil. 

The Bee Gee pumps were originally designed to use 30W oil. That being said I have cheated and use the same Trans-Hydro fluid that I use in the John Deere's as it is more convenient. Never had any problems. My D4 has a Bee Gee pump. Other than that I would use 30W as originally specified.

Thank you for all the responses. This system had hydraulic oil in it. I’ve drained the reservoir but the blade cylinders and hoses still have the hydraulic oil in them . Hmmm, decisions!  I know that I shouldn’t mix the different oils, so I’ll need to drain out the entire system. The hydraulic oil has been in there since 1960 when the Be Ge pump was installed by Berglund Tractor. The blade action is slow so the motor oil should speed up the response.
As a side note, the vibration damper had separated so I sent it to the Damper Doctors in Redding Cal. for repair. They did a great job. Which led to a radiator recored at Pankeys in Hayward and a new front pulley from Florin Tractor in Sacramento.

I hope that you are aware that the pressure on the Be-Ge pump is adjustable and your pump may only need to adjusted to improve your blade performance.

I’ve been getting by just fine using 15W-40, as that’s what I keep on hand in bulk. I’ve used Hy-Tran and Chevron tractor hydraulic fluid as well.

Not just any hydraulic oil. Try and match the original oil viscosity.
An ISO 68 Hydraulic oil would be a pretty close match.
 

i use textrans tdh in the hydraulics and trans of our d4 and in the trans, hydro and diff of the old ford tractor. it is made for use in tractor drive line and hydraulics specifically caseIH cane harvesting equipment
it is a 75w80 gear oil and close to iso68. if the hydraulics are slow that often is not the oil but the pump is not set correctly or is worn. heavier oil wont improve response speed it may make it worse. heavier oil is harder to pump than a thinner oil yes too thin wont lube properly so it important to have the correct viscosity for the temp range your working in.
dont use motor oils in hydraulic systems use hydraulic oils instead much better at separating entrained air which causes damaging cavitation and excess heating which increases wear. motor oil was used when thats what the technology was at the time.

the be-ge pumps to my knowledge are gear type pumps which are susceptible to wear of the housing were the gears run and to the gear teeth and can eventually bypass and not pump properly. same with the vickers vane as used in the cat hydro units they are susceptible to housing and vane tip wear.

if you hear a buzzing noise that is cavitation in the system. excess cavitation is bad.
the other reason for slow response is worn piston seals if they are bypassing they wont respond properly and also wont develop full power. also adding heat which causes more seal deterioration and the situation compounds. fix it properly. bandaid measures just cost more money later.