Well, when I was in the Navy, on submarines, we worked on a 120 day patrol cycle with two crews so most of the crews vehicles would go into storage for 3+ months at a clip. Our FTG chief had a farm outside groton and he would store the single guys cars for the whole time in his barn so they were covered and his kids would prep them a week before we got back. The prep included an oil change [this was also pre fuel injection days], reconnect the battery and charge it plus adding 5 gallons to the tank as they, the kids, would run them dry when they put them away. I was lucky with my customized dodge maxi-van, my parents would 'take care' of it which generally involved trips to florida, jersey shore, new england or anywhere else they wanted to go... They used to put more milage on it than I did...
It has been my experience that gas now a days will not store like it did 5 or more years ago, it seems to go bad alot faster. It used to be I could leave my wheel horse lawn tractor with a full tank when I moved it and the lawn mower to the back of the shed and moved the snow blower up front for the winter, the last few years it seems to 'turn bad' over that 4 or 5 month period and get a stinky varnishy smell to it. Same with the snow blower, now I run them dry and refill in the spring.
I would check the oil pressure with a mechanical gauge and see what the truth is..