This is an FYI for VacMaster unit owners. I bought a VacMaster VP320 in December 2020 and we love it. However, there is maintenance involved with these things. We really started using it in January 2021. I built a cart for it but needed to wait for my son and my daughter's boyfriend to be around to get it into the house. Like Bentley said, they are heavy.
Memorial Day this year my unit stopped pulling a complete vacuum. I changed the oil at the 25 hour point but did nothing with it since. The manual says "Every 60 hours, 3 months or if oil becomes discolored". I assumed since a home owner uses it so infrequently, It could go for a year without an oil change. It turns out this is not so.
The tech support folks at Ary are great. They had me change the oil and then a second time. It still didn't work. Ary tech support had me cycle the unit 6-10 times and they use Sea Foam to vigorously clean the unit. It started working while cycling my second oil change. I did the Sea Foam run for 10 cycles and then a flush with the standard oil. I then refilled with standard oil and life is good.
The bottom line is these units need to have their oil changed every three months.