I have a 93 W250 Ext Cab Automatic with 191K. After the engine (CTD) is warmed up I notice the oil pressure gauge drop all the way down when stopped in drive. If I put it in neutral it goes back up. Oil light does not come on.<br>1) How accurate are the stock gauges?<br>2) Is this common?<br>3) Any suggestions?<br><br>I plan on checking oil pressure with a quality gauge when I can find/borrow/steal one. Until then any feedback appreciated.

 

My 92 use to do the same thing, I bumped the idel RPM's up to 700 with the AC on and replaced the sending unit. Things have been good ever since. <br><br>The first thing I would do is bump the idel speed up to around 700 or so then check pressure and proceed from there.<br><br>Jim

 

Yup, I've seen this a few times too.... Put truck in gear, turn on AC and set idle to about 750 RPM. That way, you'll never draw it down so much that you loose effective oil pressure, which, can be very unpleasant later in life.. if you know what I mean..<br><br>Bob.

 

If you do not have a tach to check rpms by, a quick method would be to adjust idle, (in gear &amp; A/C on) till the mirrors stop shaking. That is just about 750 or a hair higher.

 

I would put a mechanical gauge on the truck to at least verify it's ok. when mine did that i hooked a mech gauge up and left it in, I didn't want to rely on that sender anymore (but a mech oil psi gauge is the first thing i do to everything I own...)

 

When we bought our truck, the first thing the guy said was don't rely on the stock gauges. I noticed the oil pressure gauge was just between the first and second line and didn't move when revved up. Took the sending unit out and washed out the hole with kerosene and also teed in a mechanical gauge. I have 40 psi hot in nuetral, 28 psi hot in gear, and 57 running down the road. The temperature gauge flucuates, as does the fuel gauge. I can fill up and after 25 miles, I only read 3/4 of a tank. I now know that after 360-380 miles, I have 1/4 tank left and stop and fuel. Ain't gotta round to replacing the temp gauge yet.