If the rumor is that it's being used to refuel satellites, there are two considerations:
1. Can it get to many satellites? Yes, it has good delta V, though I think you're mixing the X-37's delta V with its boosters and the delta V of the Shuttle orbiter without its SRBs and external tank.
2. Can it carry fuel for those satellites? No, not much. The X-37 has a maximum total takeoff weight of 5000 kg, while the Shuttle can get 27000 kg to LEO. Unfortunately, only one X-37 will fit in the payload bay of the Shuttle, so we can't actually lift five X-37s in the Shuttle.
Many large satellites weigh more than the X-37's total mass. The biggest individual consumer, the ISS, requires about 7000 kg of fuel annually to stay in orbit. A KC-135 in-air refueling tanker is much faster than an oceangoing supertanker, but you wouldn't use the former to empty an oil rig!
The ISS needs that much fuel to boost it's altitude due to drag in LEO. But the refueling of satellites by the X-37 is hypothesized to be at much higher altitudes where there is very little drag.
These satellites don't need altitude boosts-- they use propellant for orbital changes (e.g. to "re-task" a spy satellite to a new region). But instead of chemical rockets they often use xenon gas ion engines.
The key thing with ion drives is their "specific impulse." High-thrust chemical rockets are needed to get out of the atmosphere and perform fast burns, but ion engines are often >10x more efficient once already in orbit. And because there isn't a chemical reaction, there is less corrosion and they can last for years.
Refueling xenon for the ion drives of spy satellites would double or triple their mission lifespan. They don't need much -- maybe just a couple hundred kg. And this could literally save billions of dollars since these satellites are so expensive to build.
Where have you gotten that from? The only numbers I can find for observed Δv changes are some 100m/s for USA-212, which is a third of the OMS' rated 300m/s with a full cargo bay.
For one thing, the X-37 Wikipedia page states that a design goal was 3.1 KM/s Delta-V. That's about as official a number as I'm finding online (blah blah Wikipedia source), but there are quite a few people who track these things in the sky. Each orbital inclination or altitude change requires a minimum delta V to execute, and we can observe the results of these maneuvers here on Earth. Online arguments about the X-37 delta-V are inconclusive, we'll leave it at that!
1. Can it get to many satellites? Yes, it has good delta V, though I think you're mixing the X-37's delta V with its boosters and the delta V of the Shuttle orbiter without its SRBs and external tank.
2. Can it carry fuel for those satellites? No, not much. The X-37 has a maximum total takeoff weight of 5000 kg, while the Shuttle can get 27000 kg to LEO. Unfortunately, only one X-37 will fit in the payload bay of the Shuttle, so we can't actually lift five X-37s in the Shuttle.
Many large satellites weigh more than the X-37's total mass. The biggest individual consumer, the ISS, requires about 7000 kg of fuel annually to stay in orbit. A KC-135 in-air refueling tanker is much faster than an oceangoing supertanker, but you wouldn't use the former to empty an oil rig!