I know, I know, this topic has been covered a zillion times all over the internet but I have a different slant on it. I recently bought a gently used 2005 Sierra 1500 4.3. It's my first 4.3 and my first GMC. Today I took it in for its first oil change after driving it about 1000 miles since buying it. The oil level stayed on the full mark for that thousand miles and it doesn't leak so I feel good about it. I had noticed the gauge ranged between 20-40 psi warm before the oil change. The first thing I noticed upon leaving my mechanics lot was the gauge was reading high. It was ranging between 40-60 psi fully warmed up and idling around 45 psi cold. I knew right away they had overfilled it and when I got home I checked it. Yep. Looks like they put 5 quarts in instead of the recommended 4.5. They do a lot of work for me so I'm a little disappointed in their negligence but I don't figure an extra half quart will hurt anything. Right? But that isn't my question. Are the oil pressure gauges on these trucks really that touchy? The one on my 99 Grand Cherokee 4.0 reads the same whether it's a over full, right on the full mark or a half quart low. I can't imagine an extra half quart of oil making a 20 psi difference in the oil pressure. Am I wrong about that?
blackxpress
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I'm not sure if this is the case on the Jeep or not, but most vehicles that have an "oil pressure gauge" actually have dummy gauges. They either show "normal" or no pressure (just like a light) GM is one of, if not the only, car company I can think up that still puts a functioning oil pressure gauge in its vehicles.
Here's a ford dummy gauge. Look how quickly it snaps to normal.
Here's a ford dummy guage having issues. Heaven forbid your oil pressure was actually doing this.
Here's a ford dummy gauge. Look how quickly it snaps to normal.
Here's a ford dummy guage having issues. Heaven forbid your oil pressure was actually doing this.
No, my Jeep doesn't have a dummy oil gauge. In fact it has a brand new oil pressure switch in it. That doesn't mean the gauge itself is all that accurate of course but it reads about 40 psi at warm idle and about 60 under load, just like my truck now that the truck has a quart too much oil in it.
Go back to shop and make them redo the oil change. I was always taught that filling up a vehicle with too much oil is just as bad as not enough. On all the GM trucks I have been in they all seem to idle around 40psi warm and 45psi cold. Running at 60psi is a "no bueno". And since this is your first GMC just a friendly FYI. If your oil pressure gauge ever goes to 80PSI and stays there constantly and the truck is running fine then the sensor has failed and needs to be replaced.
Mine always runs 40-60psi, depending on engine RPM. A few psi lower in the summer when the oil runs a bit warmer, but that's where it has always been. I wonder if the engine had the wrong grade of oil in it when you bought it, 5w20 instead of 5w30?
I wouldn't worry too much about an extra half quart. The engineers design safety margins into the motors to allow for that sort of thing. If I were to guess, you could probably put 7 or 8 quarts in the engine before it actually starts to cause problems. The crank will beat the oil into a frothy, aerated mess and loose a lot of the lubrication ability because it's full of air.
If you really want to, you could crack the oil drain plug and drain half a quart of oil into an empty soup can.
I wouldn't worry too much about an extra half quart. The engineers design safety margins into the motors to allow for that sort of thing. If I were to guess, you could probably put 7 or 8 quarts in the engine before it actually starts to cause problems. The crank will beat the oil into a frothy, aerated mess and loose a lot of the lubrication ability because it's full of air.
If you really want to, you could crack the oil drain plug and drain half a quart of oil into an empty soup can.
I was going there also. Oil pressure is a factor of oil resistance to flow in the engine galleries, filter, etc and has no bearing on oil level unless the pump starts taking air because oil is too low.
That being said, a half quart is NOT going to make any difference. I wouldn't even give it a second thought if I was in your shoes and they put in 1/2 quart more than needed. When the engine is operating, you have more than that up in the galleries, the heads, etc and it will make no difference. It isn't like it is so full that the crankshaft is sitting in oil.
That being said, a half quart is NOT going to make any difference. I wouldn't even give it a second thought if I was in your shoes and they put in 1/2 quart more than needed. When the engine is operating, you have more than that up in the galleries, the heads, etc and it will make no difference. It isn't like it is so full that the crankshaft is sitting in oil.
That would be primarily from either a filter causing a higher restriction, or a higher viscosity oil. Is not going to happen overnight with anything else in the engine after an oil change.
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