After one year of ownership, I finally did an oil change with the correct oil.
I have been using Mobil 1 synthetic 5W-30. I know now that is wrong.

However, the car ran great, no oil leaks, no burn, no issues.

I put in Rotella Synthetic 5W-40 this weekend, and it now sounds like a tank. Very deep and loud engine noise, noticiable in the cabin.

It gets al little better when I hit the go pedal, but at idle, man it is loud.

Any ideas what is causing this....

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85 300CD Turbo "Das Polluter" 230K sold for $3,000

98 BMW 323is

If the oil pressure is normal...its in your head.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

All I can think of is when you jacked it up (if you did jack it up) something happened with the tailpipe or muffler.

The oil is unrelated to the exhaust system. Or so far as I know...

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)

You need to get under the hood and listen with a screw driver or wood dowel rod pressed up against the block or suspisious components like water pump, Injection pump.......heck it could be a hole in the header, exhaust pipe or muffler. Switching to Rotella 5W40.....(a thicker oil with more mass) should have deadened any internal engine noise..not caused it.
Let us know what you find.

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

It is really only at idle.

I tightened up on of the exhasut pipe hangers (the metal ones) that was loose and rattling. But didn't notice anything else.

It is a very deep resonating sound, really only at idle, and goes away upon depressing the diesel pedal.

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85 300CD Turbo "Das Polluter" 230K sold for $3,000

98 BMW 323is

If you only hear it at idle, something must be loose and rattling. Check the air filter housing mounts (press on the housing to see if the sound stops).

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I could be he needs some new muffler grease.






It will get louder with a change to a dino, heavier-weight oil. Mobil Devlac1 is thre perfered syn. oil.

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-1983 VW Rabbit LS Diesel (5speed, VNT/Giles build)

It is getting better, and may be gone without me doing anything. I did put a little too much oil in , just a few cm above the top line, but nothing crazy...

Maybe my 1 year of running Mobil 1 5W-30 was making the polluter a little reluctant

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85 300CD Turbo "Das Polluter" 230K sold for $3,000

98 BMW 323is