1988 Chevy Truck oil pressure gauge

this can be low on oil, check the level first. It can also be a clogged oil filter or it could be engine bearng problems as well. Use a mechanical guage to see if it does the same. Yours is electric and cold be giving you problems. also a good oil filter like ac/purolator/wix along with an oil change would maybe help if it hasn't been done in a while. If you drive short hops through the winter, fuel gets in the oil and thins it out then the vehicle isn't driven enough and you end up with the problem you have.