Recent Change in Oil Pressure Reading - PeachParts Mercedes-Benz Forum

BrierS · #1 08-07-2005, 03:41 PM

Within the last 200+/- miles, I have noticed a change in the oil pressure readings (according to my gauge). My '87 300TD normally ran at 3 bars with the slightest of drop at lower RPMs. Now, it moves sooner to 2 and even drops slightly lower than that at times. I was running Mobil 1 5w30 until changing oil & filter this morning. This time I put Mobil 1 10W30 and found the same oil pressure readings as prior to the change. No oil consumption and I am changing at between 3-4,000 miles.

Any thoughts on what this may indicate? The engine has 136,000 miles.
Thanks
Steve

Brian Carlton · #2 08-07-2005, 03:54 PM

Steve, why are you running 30 weight oil in the diesel?

Anything below 40 weight is not recommended. In fact, I'd venture to say that the 10W-30 oil is not rated for a diesel. Look on the side of the container. The Rotella is rated CH-4. I think that some of the better oils might have a CI rating.

Some of the fellows are running 15W-50, especially in the summer.

Can't tell you why the oil pressure is dropping, but, I sure hope it's not related to extensive use of 30 weight oil.

Sorry to tell you this, but, it's time for another oil change.

Hatterasguy · #3 08-07-2005, 05:26 PM

Yeah why are you running 30 weight? It says right in the manual to run 40 or higher.

In the summer the oil pressure will drop lower, the oil gets hot.

I would consider your currant readings perfectly normal and your old readings not.

Dump the 10W-30 and get some 15w-50 or 5w-40 at least.

pawoSD · #4 08-07-2005, 05:36 PM

It varies on my SD practically each 10 degrees it is outside, I got off the freeway on a 90+ degree day a while ago and it was idling at right around 1 bar.

After some slower in city driving it inched back up to around 1.5ish before I was home, in the colder months its always at 2 when idle.

Hatterasguy · #5 08-07-2005, 05:57 PM

Well the oil cooler has a t stat, as the oil gets warmer the t stat opens more and you will lose oil pressure.

Spec is .3 bar at hot idle and pegging at 3 bar by 3k rpm. As long as you are within specs MB says you are fine.

BrierS · #6 08-07-2005, 05:59 PM

Brian . . . read your response and went out to the garage to see what I HAD been running. It was 15w50.

Don't know what I was thinking when I bought the 30 this morning. Actually, I was thinking all of the gas jobs except my VW bus. I run 5W30 in them.

Time for my next oil change . . .

with five miles on the last one. The nearly fresh syn should be good for lubricating my barn door hinges or something (better part of $50 . . . at 8.5 qts.) Cheaper than the alternative.

Thank you all for the wake-up call. The manual does say . . . the members have posted . . . I was asleep at my own switch.

As to the oil pressure readings, the present ones are more indicative of those I have read about on the forum. I had always wondered why the '87 was giving rather steady high readinds. Guess it is nothing to worry about.

Thanks.
Steve

pawoSD · #7 08-07-2005, 06:02 PM

I've burned my hand on the oil cooler because of that T-stat.

Even when idling around 1 bar super hot mine still pegs at 3 when I bring it to around 1,200 rpm Changing those (what I thought were metal

) o-rings on the filter cover made a very slight improvement, still need to change those on the 83....

leathermang · #8 08-07-2005, 06:10 PM

Guys, Do yalls statements apply to a 1985 617 turbo , for instance ?

kirk240 · #9 08-07-2005, 06:11 PM

would a heaver oil help consumption?

leathermang · #10 08-07-2005, 06:18 PM

I run straight 40wt Delo 400 ( which is ok'd by the literature for places which remain over 86 degrees F )... because I have always increased the viscosity on engines with high mileage... due partly to a need to fill the increasing clearances in the bearings...
Some of the blanket statements at the first of this post.... or the blanket implications... don't really fit what the literature specifies....particularly since he is in NH....

t walgamuth · #11 08-07-2005, 06:47 PM

i think most would agree that if an engine is worn heavier oil would help. but not heavier than what is recommended by the mfgr. just go to the top of the range.

tom w

Brian Carlton · #12 08-07-2005, 08:43 PM

Quote:

Originally Posted by BrierS

Time for my next oil change . . .

with five miles on the last one. The nearly fresh syn should be good for lubricating my barn door hinges or something (better part of $50 . . . at 8.5 qts.) Cheaper than the alternative.

Thank you all for the wake-up call. The manual does say . . . the members have posted . . . I was asleep at my own switch.

Steve, with only five miles on that oil, I'll bet you could use it in one of the gassers without a problem. Of course, it looks black, but the amount of soot is minimal, overall, and the gasser would not have a problem with it.

Anytime.

Help is what we do here.

aklim · #13 08-07-2005, 11:33 PM

How sure is anyone that the pressure sensor is not at fault? I had the same thing happen and it came to the point that at idle, I had 0 psi. Replaced the sensor and the pressure came up immediately

Gurkha · #14 08-08-2005, 12:32 AM

Absolutely right about the pressure sensor, I don't have a oil pressure gauge, recently when I switched from Delvac Super to Delo 400, my oil temp light started coming on at idle, I panicked thinking that Delo 400 was thinning out at 45c weather, turns out, it was a faulty pressure sensor switch, same goes for temperature sensor switch, these things break and send faulty readings sending owners into a panic.

Changed my pressure sensor and now everything is fine, Delo 400 actually outperforms Delvac Super in my vehicle in terms of MPG and consumption.

pawoSD · #15 08-08-2005, 01:00 AM

I actually suspect that too, mine freaked out a little while ago when I was coming to a stop, it went erratic between 0 and 1 bar very quickly for about 2 seconds then went to 1.5 and stayed there like normal.....never happened again since.....I was about to shut the engine down as soon as I saw it move!

(paranoia-trained reflexes)

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