JK Diesel Engine Oil

[BillyOneMate]

does anyone have a definitive answer on what engine oil a diesel JK should have, because i am confused.
The owners manual states (p147):
with DPF = 5W-30 fully Synth
without DPF = 0W-40 fully Synth

Which sounds odd to me, in my (somewhat limited) understanding i would expect the DPF vehicles to require better oil so the DPF has less to filter out and therfore a longer life, but maybe i am wrong, anyone?

To add further confusion comma's website goes the other way:
5W-30 for DPF Vehicles:
http://www.commaoil.com/productsguide/vrm/6/42418/1
10W-40 for NON-DPF Vehicles:
http://www.commaoil.com/productsguide/vrm/6/42417/1

So i am confused, usually i would be inclined to go with the owners manual, but it seems wrong in this instance, or it maybe it's just my limited knowledge?

[glend]

First off the DPF sits in the exhaust stream and does not filter oil - it only traps some of the diesel particulates in the exhaust. The 5W30 is not necessarily a 'better oil', if it does not meet the viscosity grade spec'd for the engine by the manufacturer and does ot support the diesel engine ratings that a good diesel oil requires today for keeping soot in suspension (like a CH or CI grade oil). Having said that, DPF equipped engines generally are spec'd for the use of these low viscosity 'enviro' oils. The non- DPF equipped JK CRDs are spec'd exactly the same as the KJ CRDs (which were non-DPF) at 0or5W40. These VM engines have been spec'd for 0or5W-40 for some years now and this should be an indicator of the internal tolerances of the block, pistons. rings, etc. The inclusion of a DPR to meet emission regulations is some markets will affect fuel econmony (you have to push the exhaust through this filter) and increases backpressure thus reducing engine efficiency slightly. It is also likely that tighter rings are fitted to reduce blowby further which also increases internal friction. By going to a low viscosity oil manufacturers are attempting to improve the fuel economy by reducing the internal friction inside the engine - and generally speaking this works. However, the side effects of low viscosity is usually less protection (especially for an engine spec'd by the manufacturer for 0/5W40). In my opinion, if you want to keep the JK CRD running well for a long time go for the engine makers spec. Jeep service centres are now trying to put 5W30 oil in just about everything (petrol and diesel) and this reflects two things: they buy oil in bulk under contract and generally don't hold a lot of different blends; and they are complying with policy on focusing on returning fuel economy to owners at the expense of engine longevity (it will probably be out of warranty before this becomes a problem for them). I own a KJ CRD (with the VM2.8 and run 5W40 as spec'd by my owners manual and VM). My son owns a JK Unlimted CRD.

[BillyOneMate]

thanks for the detailed reply.
So the below 5W-40 oil should be fine then, and certainly better than a 10W-40?

http://www.commaoil.com/productsguide/view/6/176/SYD5L

[Stevil]

I have an 07 CRD and run the 5w30 synthetic, zero oil consumption after 125000km. I reckon its done the Job !

[jbee]

I think for the Auto CRD - it has to be the 5w30 ESP not straight 5w30

[Trigger82]

Does the owners manual for the Diesel Say anything about using a grade of oil like C3 or DL1? if so it would be best reccommended to use these. If the Diesel's run a DPF filter and you dont run a oil that meets the Specs (dont confuse with oil weight or thickness) it will slowly block the DPF all the one we've replaced at work are in the vicinity of 3-4000 dollars and not warratable if found to be using the wrong oil.

[davidd]

are these dpf or cat converters that are blocking mate?