Thread: Oil Question Again

Originally Posted by Briar

Hi Shane

Enjoyed your vid. Very informative.

I noted in your video that you siad (I think) that you were running GM Dexos 2 5W40, but in a reply to a comment I think you said you were running Valvoline Synpower MST 5W40.

My next service will be in a months time and I'll be at about 197,000km. Since new it has always run the C1 Penrite 5W30 Enviro. Engine is very quite and virtually no clatter on startup. Also longer trips as I live 20km out of town, so always gets fully warm when driving. I don't flog the vehicle or bore it into it. I am towing the van a lot more so considering the arguments for 5W40 seriously (by you and Christian and others). What would your suggestion be and why for which oil to go to. Appreciate your thoughts.

Seriously, stick to your C1.... no need to shift to the 40 weight

Originally Posted by Briar

Hi Shane

Enjoyed your vid. Very informative.

I noted in your video that you siad (I think) that you were running GM Dexos 2 5W40, but in a reply to a comment I think you said you were running Valvoline Synpower MST 5W40.

My next service will be in a months time and I'll be at about 197,000km. Since new it has always run the C1 Penrite 5W30 Enviro. Engine is very quite and virtually no clatter on startup. Also longer trips as I live 20km out of town, so always gets fully warm when driving. I don't flog the vehicle or bore it into it. I am towing the van a lot more so considering the arguments for 5W40 seriously (by you and Christian and others). What would your suggestion be and why for which oil to go to. Appreciate your thoughts.

Dexos 2 is a specification, which synpower MST C3 5W30 and 5W40 both have approvals for.
Honestly, I personally look for known quality specifications as a primary then the viscosity. I mainly run a 40 grade due to regular towing that puts a little more heat load into the oil compared to unladen driving. Not really much difference between a C1 and C3 anyway in regards to performance targets, C1 will have a little more sway to fuel economy side. I'm not personally convinced that 5W30 is the cause of engine failures in the TDV6's for what its worth. But on the other hand I have seen a small improvement to wear rates in oil samples with the 40 grade over a 30 - is the improvement significant? Probably not that much in it really.

5W-30 vs 5W-40 (at the correct spec) is really just a personal preference in the end. One will give a marginal benefit in fuel economy, and the other a marginal benefit in engine wear.

What most people don’t discuss though is the normal temperature the oil operates at. 5W-30 suit engines in cool climates that typically see the oil temp sitting around 90-95 degC. This is the oil spec that matches the required viscosity to the bearing clearance when new.

But if you are in a hotter climate, or do lots of towing, and see engine temps sitting 10-20 degC higher then you increase the SAE oil grade by 10 to bring the viscosity back up to about the same level as the cooler operating oil. This keeps you away from the oil becoming dangerously thin at these higher temps. 5W-30 oils become very thin at 120 degC.

The Citroen engineers were not wrong to specify 5W-40 for hotter climates for the same engine. But they are the only car manufacturer using this engine that are matching oil viscosity to bearing clearance under different climatic conditions. The rest just took a simpler approach.

The other factor is then age - as the bearings approach their service limit it is normal practice to increase the oil viscosity as bearing clearances open up. What is the expected life of the bearings? - who knows - but if you are over 250,000 kms you are probably near mid-life and increasing grade by 10 can be beneficial.

As Shane notes - it probably makes very little difference, but for a borderline design it is these small differences that gives you long term reliability. Especially if you believe an engine and car should last a lot more than 500,000 kms.

Changing the oil twice as often as needed probably gives you more benefit if you are really concerned and don’t want to move away from the original (when new) oil spec. And if you are in a cold climate - stick with 5W-30.

But for warmer climates or worn engines, changing to 5W-40 is not a dumb thing to do - especially for the older D3/D4’s with the 2.7TDV6.

Shane’s video was incredibly detailed and high level but made it super easy to understand the bias of each oil spec. Apply that against your type of use and environment. A Tassie D3 is in a different world to one in the Pilbara. A next level up from Christian.

Originally Posted by PerthDisco

Shane’s video was incredibly detailed and high level but made it super easy to understand the bias of each oil spec. Apply that against your type of use and environment. A Tassie D3 is in a different world to one in the Pilbara. A next level up from Christian.

Correct - and most D3/D4’s sold around the world operate in conditions more like Tasmania than the Pilbara. Which is why Christian calling it 5W-dumbass-30 is misleading.

And despite both having a 5W rating, the 5W-40 oil will still be thicker at very cold conditions and so you will see very high oil pressure during cold starts in very cold climates.

I wouldn’t use 5W-40 in very cold climates.

Just putting it out there, and I'll get slammed, but anyway.

I've never seen a 3.0l crank failure due to oil, all have been cracked in the same spot, no bearing damage. Id love to see more close ups.

I can find 2.7 issues, only early on, spun bearings etc, but not 3.0L.

So unless someone has a better photo.. All the oils are fine.. It's the steel that's the issue.

I run the 40w, I love the beach, trailers and I'm old 300k

Originally Posted by DiscoDB

5W-30 oils become very thin at 120 degC.

It's not uncommon for me to see >120C oil temps when towing. I have a manual, keep the revs up, rarely exceed 95 and the van isn't big or heavy. I've seen nearly 130C pulling hard up Sues road when I was "seeing what it could do". That's *sump* temp, which is always lower than the oil in the bearings.

I'd have thought pulling a decent load with an auto that has a propensity to lug resulting in higher combustion pressures, higher EGT, coolant and oil temps would warrant a bit more investigation.

Originally Posted by Tombie

There has already been reports of vehicles running warmer with the thicker oil.

This could be correct if using 5W-40 in very cold climates - if the oil is too thick there is more resistance and fluid friction which then generates increased temperatures.

Too thin in hot climates also generates higher temps due to insufficient film thickness and metal on metal contact.

Needs to be at the goldilocks point - not too thick and not too thin at the bearings operating temperature.

Would be interesting to know where these reports were from. Have not seen any increase in oil temps in my case.