"Now, if you are using an attachment that requires both standard flow and high flow at the same time, you need to order a second auxiliary hydraulics kit from your dealer," he notes. "Attachments that would use both standard and high flow would be those that have a positioning cylinder, like some rock saws or cold planers."

Attachments dictate flow choice
The biggest downside of high flow is the added cost. "There is a slightly higher price for the high-flow models due to the additional high-capacity components included with the option," says Moore. "The price increase varies from approximately 3% to 5%."

Depending upon the manufacturer, the high-flow hydraulic option can add $1,850 to $2,600 to the cost of the machine. However, Zupancic asserts, "This is a small price to pay for significant increases in a machine's potential hydraulic output. The increased hydraulic flow and power mean better performance for the attachments... This is especially useful for improving production of attachments that demand a lot of hydraulic power, such as a 5-ft. trencher, snow blower, tree shredder, cold planer or large mowers."

Yet, high flow is not the right choice for every application. "A standard-flow machine would be a better solution in applications where an attachment is used that does not have the hydraulic horsepower requirements of a high-flow system," says Giorgianni. "An example would be a scrap grapple, in which the auxiliary hydraulics do not require the high horsepower and flow to drive the grapple open and closed."

"A standard-flow machine is better when all the customer needs to do is dig or lift material the majority of the time," Zupancic states. "Maybe occasionally they would use a hydraulic auger or smaller trencher. In this case, the added cost and complexity of a machine equipped with high flow would be a waste."

Attachment usage ultimately drives the decision. "The choice of whether or not to order a machine with standard-flow or high-flow auxiliary hydraulics really depends on the hydraulic flow requirements of the attachments," says Hughes. "If the optimal flow for the attachment (as recommended by the attachment manufacturer) falls within the range of the machine's standard flow, high flow is not needed."

For example, the standard auxiliary hydraulics on Case skid-steer loaders and compact track loaders range in flow from 19.5 to 23.8 gpm at rated engine RPM, depending upon the model. "So if you are running an auger that has an operating range between 6 and 15 gpm, standard auxiliary hydraulics will work fine and there is no need for high-flow hydraulics," Hughes points out. "However, if you are running a cold planer, your hydraulic flow requirements are going to be much higher."

Most of the cold planers the company offers have a flow range of 22 to 40 gpm, meaning that standard-flow hydraulics would not allow the attachment to operate at optimum efficiency. The optional high-flow auxiliary hydraulics provide a flow of up to 41.8 gpm at rated engine RPM, depending upon the model. "So in order to maximize productivity and most efficiently run the cold planer, you would need to order the high-flow hydraulics option," says Hughes.

Yet, the majority of attachments on the market today operate within the standard flow range. "Most attachments can run with standard auxiliary hydraulics," Hughes acknowledges. "However, our customers who need high-flow hydraulics [because of the attachments they run] understand the benefits and order their machines with the high-flow hydraulic option."

Zupancic agrees, adding, "Customers usually understand that if a specific attachment requires a minimum flow to run efficiently, they will need to match their machine minimum flow output to run those attachments. Depending on the model size, John Deere sells 10% to 20% of their machines with the optional high-flow system."

Gehl reports it continues to sell more standard-flow skid steers than high-flow units. "The majority of attachments available today are standard-flow attachments, and the majority of applications can be completed with a standard-flow system," Moore points out. "Standard-flow attachments are efficient and perform satisfactorily in these applications."