15w40 - What minimum temperature?

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Hi Guys,

Bit of a back story to thus one for those who are interested...

Our Dacia Duster is spec'd for either a 5w30 ACEA C4, 5W30 ACEA C3 or 5w40 ACEA C3 oil.

We bought the car on 3,500miles at 1 year old. The supplying dealer used a 5w30 C4 oil. The oil was being used at a rate of 1 litre every 1000miles.

At 5,000miles I got suspicious that the oil filter didn't get changed at the supplying dealers service. The area was far too clean considering its downwards tilted and the oil filter was ridiculously tight (quite a few mentions online about Dacia's and Renault's with the factory fitted oil filter being very tight). So I changed it out for Shell Helix Ultra AG Dexos 2 5w30 ACEA C3.

Again, this got consumed at a rate of 1 litre per 1000miles, although it did tail off a little towards the end.

When the car hit two years old I got it serviced by a garage for warranty purposes and supplied Fuchs GT1 XTL 5w40. This is a 5w40 ACEA C3 oil are carried s ton of approvals like LL04, 229.5, Dexos 2, 502/505 etc.

And the consumption stopped, dead. It hasn't used a drop of oil since.

6 months later and 5,000miles I'm ready to change the oil again. Probably premature but the car does a llot of short tripping.

I would like to try a 30 weight again in the future (maybe Castrol 0w30 C3/Dexos 2) and see if it starts burning again. But, at the moment I have in my garage 15 litres of Morris Lubricants HD4 15w40. A HDEO that meets ACEA E7 and E9. I see no reason why it would cause any issues in our Dacia for the next year or so.

However, I was concerned about the lowest usable temperature of a 15w oil in this engine. The lowest temperature I've seen since I've been driving is 11C/50F.

Will the 15w40 be fine through winter?
 
Someone will be along shortly with the actual scientific answer, but in the meantime, here's my anecdotal response - my six cylinder, 4 litre Ford Falcon has a sump full of 15w40 and starts at zero degrees Celsius with no issues, no VCT rattles, nothing. And in years gone by, everything here ran 20w50 - again, winter starts, although not as cold as you'll probably get, were a complete non-issue.
 
And one of the scientific answers is looking at the Cold Cranking Simulator (CCS) data.

0W. -35 C
5W -30 C
10W -25 C
15W -20 C

It says 15W will crank at a acceptable rate down to -20 C and I believe the anecdotal information supports that. However, if you want to be kind to your engine, at -20 C I personally would use a 0w40 or 5w40 because there are so many good HDEO's avaiable in those weights.

As for your temperatures, absolutely no problem.
 
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-6*C (20*F) is on the higher end of what viscosity charts say. Seems to be somewhat of a grey area really.

Although, plenty of people have used 15w40 in much cold temperatures with no block heaters without issues... I say go for it.
 
You could 50/50 mix with 5W-40 in the winter if it makes you feel better. You are in South Wales, I don't expect you see much of anything that resembles a "Harsh Winter" like I have known (-40°F /-40°C)

I have started a LOT of engines in that cold temp with 15W-40 in the sump.
 
i never use 15w40 oil even in hot and dusty area since engine nowadays is very accurately with more precision. in my place even diesel engine and i always hauling using 10w30 CL4
 
The owners manual from my wifes 2002 Superduty Ford F250 with the 7.3 diesel engines oil viscosity chart recommends 17*f or 8* C.
 
Any 15W is easily good enough down to freezing.

However, it does depend on which oil you choose. Mobil 1, 15W-50 synthetic is still pour-able at -40 and will work very well at any temperature above 0 degrees F (-18C )
 
In general, mixing does not improve the low temperature ability very much. The hydro-carbon molecules that turn into a wax of the 15W oil will still turn into a wax at exactly the same temperature. With a mix you will have a sludge of wax and liquid at the temperatures that are below the usable temperatures for the 15W, and above the minimum temperature for the lighter oil such as a 5W.
 
At 50F my motorcycle with its tiny little starter and puny battery cranks and starts just fine with a sump full of monograde SAE 40 (no W rating).
 
So you want to risk switching to another oil that may bring back the oil consumption? I would stick with what appears to have worked very well, Fuchs. They make really good stuff.

As they say (stateside at least), if it ain't broke don't fix it!
 
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Sorry guys,

Made a mistake this morning. How, I don't know?

Bottom temperature here I've seen since I've started driving is -11°c/12.2°f.

I'm sure you all thought I was nuts in the first post, wondering why I thought a 15w oil would be an issue at 50F. And those who know the part of the world I live in must have thought I hibernate during the first 3 months of every year, I wish!

I don't think for a second that a 15w40 HDEO would cause the engine to start consuming oil again.

I'm also unsure why it consumed oil at first. My theory is the old couple who owned it before me drove it very gently and the rings didn't bed in properly. My Wife drives hard which probably helped bed the rings in again. I wonder if it's just a confidence that it stopped burning at the same time I changed the viscosity?

I'll try another 30wt, I'd like to not just to see if it still burns but I'd like to try the Castrol Edge 0w30 C3 oil as it's a Group 4 base oil.
 
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i would stay with what worked + if you have a "cat" its life will be shorter as you send more consumed oil at it. beside the viscosity oils still vary in cold flow depending on the base oils group. another thought is even an oil flows at said temps the slower flow may be starving critical parts of lubricant!!
 
Stay with what worked in your engine...

Plus...be aware that "low saps" in HDEO is not equal to "low saps" for PCMO...

Acea E9 has more ash as C3/C4...
 
I assume your Duster is still under warranty so I would keep to a grade that's one of the recommended ones. 15W40 is fine for top-ups but I would not change the whole system to that because it's sitting on a shelf in your garage.

I recently changed my Audi to Fuchs Titan GT1 Pro Flex XTL 5W30 which is A3/B4 spec. However, they are produce a similar 5W30 with C3 specification that you can buy online from Opieoils for around £26 for 5 litres.

Just for interest, how do you know that Castrol Edge is Group 4 based?
 
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