c dailey

Had my oil changed yesterday at my local dealer.My truck always holds around 40#'s of pressure,well when i stopped at the gas station last night on my way to work when i came to an idle my pressure droped down to about 0.but when i give it gas it only goes up to 30 to 34#'s,but the truck is still running great,no nocking,ticking or anything.Checked my oil it was over filled about a half inch over the full mark on the dipstick dont know if this had anything to do with it or not.Took it back to the dealer this morning,and they changed the oil pressure censor for no charge,and the guy told me it took care of the prob. fora few min. then went back to doing the same thing (dropping pressure at idol).ANY SUGGESTIONS?

z28dragracer

How many miles are on the motor? Also did they go with a lighter weight oil? My tahoe does that if I put the original 5-30. I use 10-40 due to higher mileage.

73shark

Not sure but if it was over-filled too much, I've heard that the crank windage can foam the oil to the extent that the pump can't pump it but since you said it's OK off-idle, I doubt that's it. z28's answer is probably the most likely.

RacerX

Unless you live in the Arctic Circle or something there is no difference between 5w-30 and 10w-40. Oil viscosity is based on weight in a specific temperature range. Thin when its cold, thick when its hot. All you gotta know is the temperature that specifies the cold/hot range.

73shark

So you're saying that @ 30*F, 10W is the same viscosity as 5W and 40W is the same as 30W @ 100*?

RacerX

They put the chart on the back of every bottle of motor oil. You ll see the temperature zones overlap. And I dont know where most of you guys live, but in New York, it really doesnt matter. It seldom gets that cold or that hot that you ll know the difference between 10W30, 10W40, 5W30 or whatever else they offer. I worked at 3 different new car dealerships Ford, Chrysler and Toyota that respectively had different weight oil at the tap. And not because it was required but because it was what the guy brought in the truck. And then who knows about the quick change places and smaller shops? You know they dont have 7 different taps for all weights of motor oil. There is one tap to do it all.

But for the guy in Arizona or Alaska, these numbers may be important. But then again you can always add synthetic. 0W as it is.

c dailey

well got back with the service guy today truck goes in on tue. the 25th he thinks the oil pressure gage may be bad.Hence i dont have any service engine light on and no codes,and the bad bow tie is running great.I also called my cousine who works for a local mercury dealer,and he said the same thing,especially knowing if the pressure was dropping down to almost zero he said the motor would have been making all sorts of noises,and prob. blowen up by now. LOL. oh and they have allready put a new oil pressure censor on and that didnt help.Well thanks guy's for the input very helpful and i will repost in a day or so to let u guys know how it went.

73shark

Just have them install a temporary mechanical pressure gauge.

c dailey

well the dealer checked voltage for the gage that came back working fine ,then they put mechanical gage on and that showed their was low oil pressure in the engine.they couldnt diagnos the prob. without tering down the engine,that i dont have the money for the service guy called my extended warranty comp. and they said 8#'s is within specs of chevy,so they wouldnt authorize them to tear the motor down what a bunch of @#!%.the dealer said that was fine but the computer is saying otherwise thats why the info ctr. light is coming on.any other suggestions guys im thinking oil pump,and taking it to a local shop tommorow that the service guy recomended that would be a little cheaper than the dealer.oil pump $900at dealer $150 thru napa WTH.THE funny thing is motor makes no bad noises at all u would think a bad berring would cause some sort of noise.I have heard bad berrings will cause low oil preasure.

in2pro

It would be my thinking that if its dropping now, it will eventually continue to drop to nothing and will cause engine failure most likely when you least want it to.