Big CRD diesel engines in heavy cars (like ours ) are considered performance engines, especially when used as commuters (like I do)
I travel 1100 km each week in heavy traffic and cruise mostly (when possible) at 140 km/h.
Due to the amount of miles I drive (>40K miles/year) I need oil with high OCI so in my case there is no other sane choice than to use quality full synth oil.
Now I change oil twice each year, with mineral oil that would be 4 times

 

Good reason for you using fully synthetic then. I used Triple QX semi from carparts4less last time and I see they have Full synthetic at mo for £17.94 so why not. But still got a spare 5ltr in stock so no need.

 

Oh here its dead tonight so I'll add a wee snippet about Triple QX just incase you think its cheap stuff.
Blended in UK and sold exclusively by Euro Car Parts. 10w40 semi meets VW500.00, 505.00 and MB229.1.
While 10w30 satisfies Ford's stringent M2C-913A/B for diesel engines.
Range topping 5w40 fully Synthetic meets VW502.00, 505.00, MB229.4, BMW LL-01 and Renault RN700/710.
So there take it or leave it, its cheap stuff, but good.

 

Triple QX is typical British oil, I have never seen it for sale in the Netherlands, the specs for the synplus C3FS seem pretty good tho.

here in Holland I use Shel Helix Ultra 5W30 , not very cheap but because I extend my OCI to >20k km I want an oil proven for its high amount of dopes and additives to last that long.
Calculated per km the price is not that bad

 

Yeh I see the shell site has got the CRD down for Helix Ultra 5w40. So do you find its better with the 5w30.

 

5W40 is advised but 5W30 can also be used in our CRD's
In theory the W30 should be a little better on fuel mileage due to slightly less friction (oil thinner) at working temperature.
Also since our CRD's have the tendency to stay on a low working temperature (my temp gauge always stays below half) 5W30 would (imho) be preferable.

 

In all due respect, I come from a Heavy Diesel Commercial back ground, we used a mid range known oil (not cheep by any means) semi synthetic and changed the change intervals by half, never had an engine fail to inferior oil, have had a few fail due to losing oil in a hurry!! but people that go on about how long their oil will last to me are wrong, have they ever seen oil that has come out of an extended service vehicle? its like Syrup, what's better a good oil change at 1/2 the mileage for lets say £40 including the filter if you do it your self, or stuff an engine at 4k plus????

 

Heavy diesels these days should have a life 0f 50000 miles. If you bought 10 trucks at the same time all with the same engine and age used in the same conditions and with identical service intervals, sump size and oil properties you would get 5 trucks at 50000 and 5 trucks at 25000 because the drivers were different. Duty cycle and drivers make or break HGV oil degradation.

Of course here we are talking cars, and light to normal use cars at that. Anyone on dusty forest tracks or a 'taxi' cycle type 24 hour town use would of course fit into the half-life cycle. Our American cousins might travel megga miles, here in the UK its and unlikely scenario. The fuels in both commercial and retail vehicle's and the quality of filters suggest there's more damage caused by the dirty and infrequent filters change[s] than oil. The industries all over the world tell us / want us to :

- change your tyres 4 times a year
- change your oil every week
- add this expensive voodoo and that Paul Daniels snake~oil or your radiator / engine / trannie etc will die

It's marketing, money making, a scam !

 

I see Google was your Friend!!! All I will say is anyone that stretches their oil changes to what the advertising hype says is foolish, oil is cheep compared to a new engine. even the artical says get a bad driver and your oil is going to take a pasting.

Optimizing Oil Change Intervals in Heavy-Duty Vehicles

 

@John Norish
True, oil is cheap compared to a broken engine, but modern (semi) synth oils (base and additives) are so much better than the oils where only a few years ago that OCI in modern cars have doubled at least, same goes for heavy duty dieselengines (even in big trucks). I guess your experiences come from the past?
Though you can choose to "play in the safeside" and half your OCI, thats your choice, but imo you are only hurting your wallet and the environment.

The 2002 recommendation from Chrysler for my 2.5 CRD was an OCI of 9.000Km but I do >20k Km with a good full synth oil. The old oil comes out like I could do another 10k km with it My engine runs like a charm and continues to do that, it still uses as good as no oil after 300k km (with those long OCI's ).
My car mechanic did send a dozen oil samples from similar cars with similar OCI to the lab to do oil analysis and concluded 20K km is very muchon the safe side for an OCI. After 20K the dopes and additives of a good Synth oil (Shell Helix) are still not worn out and the viscosity is still perfect.

recently car manufacturers like Toyota recommend a 10K miles OCI using full synth and they are absolutely on the safe side

So its everyones personal choice what to do with their OCI, but halving an OCI seems foolish imho.

NB. My opinion is based on personal observations and the result of years internet researching this issue and participating in many many discussions with specialist on this matter. My opinion is about the same as the consensus of professionals in the field.