I've got an old 87 model 4x4 pickup. Mainly just use it as sort of a Polaris ranger. 3.0 v6 150,000 original miles very quiet smooth running engine. It has a after market oil pressure gauge mounted to the dash. This afternoon I noticed the oil pressure was about 75% of what it usually is. I can buy a new gauge for 20.00. Would that be the 1st thing to try?