Why not use 0W-20 in a diesel engine?

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After reading the "Why do Euro cars use heavier oils post below" and the mention of diesel engines, I got to wondering: Why don't diesel's use 5-30 or even 0/5-20???

And maybe it's because it's a US grade thusfar...so what is the recommended grade for US diesel cars...eg. E class M-B or diesel Golf/Rabbits???
 
They don't because they would wear out faster. Engine design dictates ideal viscosity. Torque vs RPM relationship is also a factor. High torque at low RPM requires thicker oil. On top of that, soot acts as an abrasive in diesels so thicker film thicknesses are needed than if there were no soot.

5W-40 is used for late model VW TDI engines and MB diesels.
 
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5W-40 is used for late model VW TDI engines and MB diesels.




That may be true for VWs but the factory fill of 229.31 and 229.51 diesel oils in Mercedes cars is 5w30.
 
I thought MB dealerships were using the new lower-SAPS Mobil 1 5W-40? I forget it's letter designation but it's not 5W-40 TDT or Delvac 1. Correct me if I'm wrong. Maybe what's factory fill is different from what's used thereafter. Same with VW/Audi in many cases.
 
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I thought MB dealerships were using the new lower-SAPS Mobil 1 5W-40? I forget it's letter designation but it's not 5W-40 TDT or Delvac 1. Correct me if I'm wrong. Maybe what's factory fill is different from what's used thereafter. Same with VW/Audi in many cases.




If you look at the 229.31 and 229.51 approval lists the vast majority of oils on there are Xw30.

MB sheet 229.31 approved oils; LA "low ash" Oils
Mercedes pioneered this new spec for passenger cars with diesel engines with EURO 4 or Bluetec exhaust particle filters, e.g. W211 E200 CDI, E220 CDI. The spec was introduced 7/2003. They are called LA "low ash" or "low SAPS" oils, low on sulfated ash, phosphorus and sulphur to limit exhaust particle filter pollution. In 2004 the ACEA introduced the new C3 spec (mid SAPS, normal viscosity) based on it. Change intervals extend to 15,000 km.

30
Aral Tronic 229.31 5W-30
BP Visco 5000 MB 5W-30
Castrol FORMULA SLX Turbo Diesel 0W-30
Castrol TXT Softec MB 5W-30
Fuchs Titan GT 1 5W-30
Liqui Moly TopTec 7000 LA
Low SPAsh Motorenöl 5W-30 (DaimlerChrysler) (factory fill)
Midland Synqron 5W-30
Mobil SHC Formula LA 5W-30
Mobil 1 ESP Formula 5W-30 (from 3/2005)
Q8 Formula Special 5W-30
Pento High Performance 5W-30 LA
Shell Helix Diesel Ultra AE 5W-30
Shell Helix Ultra AE 5W-30
Wintershall ViVA 1 topsynth alpha LA 5W-30
40
Aral SuperTronic 0W-40 LOW SAPS (ACEA C3)
Castrol GTD Magnatec 5W-40
Fuchs Titan GT 1 10W-40
Liqui Moly TOP TEC 4100 5W-40
Midland Synqron 5W-40
Motor Gold Mid SAPS 5W-40
Motul SAE 5W-40 Vollsynthetisch
Pento High Performance 5W-40 LA

MB sheet 229.51 approved oils; low ash long life
Mercedes pioneered this new spec for passenger cars with diesel engines with EURO 4 or Bluetec exhaust particle filters and longer service life than the 229.31 oils. The spec was introduced in 2005. Change intervals increased to 20,000 kilometers. Based on ACEA A3 B4 and C3.

Amsoil European Car Formula 5W-40
Anglomoil RoadMaster 500 API SM 10W-40
Aral SuperTronic 229.51 0W-40 LOW SAPS
Castrol Longtec Turbodiesel 0W-30 (229.51)
ELF Solaris LSX 5W-30
Fuchs TITAN GT1 229.51 SAE 5W-30 (first fill oil in OM 642)
megol Motorenoel New Generation SAE 5W-30
Mobil 1 ESP Formula M 5W-40 (to become available in the USA on 5/15/06)
Mobil 1 ESP Formula 5W-30 Emission System Protection (Europe, from 12/05)
Shell Helix Ultra AX 5W-30 Mercedes 229.51
Valvoline SynPower MST 5W-30 229.51 (added 6/1/2006)
 
Thanks G-Man. Valvoline 5W-40 available in North America is claimed to meet MB 229.51 now too. XW-30 oils meeting those above specs still have HTHS>=3.5cP, so have some "thickness" to them just like GC does.
 
There are a few UOA'a on a diesel truck on this forum showing very low wear on a #20 viscosity due to fuel dilution. But if you start at #20 there's zero room for fuel dilution.
 
IMHO, diesels test out the HTHS specs in the huge pressure spikes (that you hear, while at University, we were taught that diesels are a constant pressure hat addition), thinning the wedge badly.

So the manufacturers want an OIL to be there, so they traditionally specified straight 30s. Reluctantly they accepted multi-grades, but chose 15W-40, which is almost achievable with a straight weight decent base stock oil.

My Nissan TD calls for a 10W-30 HDEO (not exceeding CF-4, must have JASO DH-1 etc).

Amsoil "straight" 10W-30 would prolly do the job, except that it's a "better than CF-4 oil)
 
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5W-40 is used for late model VW TDI engines and MB diesels.



Newer VW/Audi TDI engies requires VW 507.00. Almost all of those are 5W-30 or 0W-30. At least that's the recommendation in Europe. Maybe it's because the diesel here is "cleaner".
 
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5W-40 is used for late model VW TDI engines and MB diesels.



Newer VW/Audi TDI engies requires VW 507.00. Almost all of those are 5W-30 or 0W-30. At least that's the recommendation in Europe. Maybe it's because the diesel here is "cleaner".




Not arguing, just asking: Is the diesel fuel in Europe still cleaner than the new ultra-low sulfur diesel fuel that is now being sold in the USA?
 
Light Duty diesels in Car's and 1 Ton trucks might be able to handle it but the top end wear would be accelerated. A heavy duty commercial Class A,B work tractor/truck would wear the top end out in a matter of weeks! The spring loads are just to great.I also have some reservation about the average HTHS of most 20W oils for the bearing and wrist pins but with the right material and a 20W built like Redlines it might be doable for the lower end. If they did away with spring and cam accuated valves and went to phuematic or eletronic actuators it would be a huge step to makeing it happen.
 
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Not arguing, just asking: Is the diesel fuel in Europe still cleaner than the new ultra-low sulfur diesel fuel that is now being sold in the USA?



I said maybe because I wasn't shure
smile.gif
 
Quote:


Not arguing, just asking: Is the diesel fuel in Europe still cleaner than the new ultra-low sulfur diesel fuel that is now being sold in the USA?



ULSD in the US is 15 ppm or less. In Europe the diesel is 50 ppm or less -- but is supposed to be reduced by 2009 or 2010. Not sure what the new limit will be.

On the topic: I've tried a 0w30 oil, and gone back to Mobil 5w40. I don't know much about oil, but I know what didn't work.
 
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