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83 300sd
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Discussion Starter · #1 ·
Just changed the oil in my 300SD and 2 days later the oil pressure seems to be hovering around 1.8-2.0 at idle and only goes up to 3 when I step on the gas. It's an 83 and I replaced the filter and used 15-40 Tellus.

It used to always be at 3. What's up? Is this normal?
 

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'91 560SEC
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940 Posts
as long as the oil pressure stays at 3 while you're accelerating, then there isn't a problem
 

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1982 380 SEL
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235 Posts
Good because I just noticed the same thing with my car after the first oil change last week.

I was wondering though, what does the 10w20, 5w20 stuff mean as far as oil? I'm pretty sure I bought the mixed synthetic castrol gtx 10w20. I was a bit low on cash, so next time I plan to use the mobil 1 synthetic. Should I be using 10W20?
 

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Depends on the day!
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Woahh....that couldn't be more off weight wise if you tried.. You need to be running 15W40 or ideally 20W50 in the summer.

Also, your oil pressure is nearly ideal.

10w20 is WAY to light.

Jonathan
 

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1982 380 SEL
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jhodg5ck said:
Woahh....that couldn't be more off weight wise if you tried.. You need to be running 15W40 or ideally 20W50 in the summer.

Also, your oil pressure is nearly ideal.

10w20 is WAY to light.

Jonathan
oops. So the "_w_" refers to the weight of the oil. I don't remember seeing 15w40 or 20w50, although I did buy it at walmart because it's very close to my house. Assuming that Walmart does not carry them though, should your standard autozone or o'reilly auto parts have it?

Also, is it worth another oil change to replace it with heavier oil, or is it safe to wait another 3,000 miles?
 

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1991 300 SE
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The reading depends on engine temp and type of oil used. Hot oil is thinner and will flow easier, hence lower pressure to pump the oil. Synthetic and lighter oils like 10w 30 will also flow easier and require less pressure to pump. A cold engine should read 3 bar always. When warm the pressure can drop to as low as 1.5 bar as long as the pressure pegs back to 3 under throttle.

For hooligan the fresh oil is flowing easier thus the lower numbers. For Dustin if you’re using synthetic, a blend, or a lighter oil, you’ll also see lower o/p numbers. I’d recommend either full synthetic or 20w 50 for summer, as Jonathan noted.
 

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1982 380 SEL
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Thanks!
 

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83 300sd
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Discussion Starter · #8 ·
Thanks everyone. I was getting really nervous about it. Now I feel a lot better. Thanks.
 

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1984 380SE
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Question

I just changed my oil and used Castrol 10w40 and used a FRAM filter. If I am reading your post correctly it is normal for the oil pressure gauge to be pegged at 3 during acceleration and when I idle it is at 2. This is OK?

Thanks,
Jayson
 

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1984 380SE
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I just changed my oil and used Castrol 10w40 and used a FRAM filter. If I am reading your post correctly it is normal for the oil pressure gauge to be pegged at 3 during acceleration and when I idle it is at 2. This is OK?

Thanks,
Jayson
 

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I 2nd the 15-40 and 20-50 idea.
And most of us have high miles ( over 150K ) I would use a high weight.
and you dont need to change every 3k . you motor is burning it up with blow by anyway so you probly have to add oil ever 2K anyway. change 5k or maybe even 7K
 

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1990 Mercedes 560SEL
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For some reason, this post did not pop up during my searches. So I posted one just now with pictures. I have Quaker State 15W40. But when pressure falls down to 1 at low speeds and high temperatures, the car's engine appears to die down. But it doesn't. If I put it in Park, the pressure goes up to 1.5. And while accelerating, it goes up to 3.
 

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are you loosing power ?
if not then try changing oil filter maybe its clogged
if you loosing power try fuel filter
winter oil 10-40 ( real winter , like states with snow )
 

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what is the problem with oil pressure? Anything that doesn't turn the light on is fine. Less than 1 is o.k. I would run the highest number you can find if you want the pressure to be high. 30w or even a straight 40w won't hurt anything and if it makes you happy then so much the better. As long as it is a synthetic oil then you're good to go. If the oil pressure light comes on then stop the engine and get towed otherwise keep on truckin.
 

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' 91 350sel, '12 s350, '18 144 sprinter, '08 sl550
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i run mobile delvac 15w40 in all my diesels , except the coldest months the gmc duramax get s t6 rotella 5w40, being the daily driver, it starts much easier in jan/feb months.. wallmart has both my area.
 

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Chad, I used Castrol 10w40 is this ok or should I drain and go with 15w40 or am i good until next oil change.
10-40 is ok. I would just go back with 15-40 next oil change
no need to dump it. 10-40 is not thin enough to worry about it.
just as engines get high miles on them the gapes between bearings ,etc is a little larger and it takes a little thinker oil. too think is bad I.E. also like if you were to dump 80weight gear oil it would not travel to the bearing fast enough to protect them
 
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