I got caught with about 2-3 days where temps in my area dipped below 20*. Maybe down to 12-15* just during morning start ups and I needed to use my truck but didn't have time to change to 5w-40. Can someone put my OCD mind at ease and reassure me that I'm worrying about nothing with this viscosity at those temps under such limited use? I would assume if there was potential for harm there would be huge warnings and absolute directives to avoid.

 

Are you talking 12 above ? You live in the sunny south ? We didn't get upto zero for a week. Anyway No you won't hurt your engine

 

Block Heater?

 

I would be careful with the low temps running 15w40. If you can't change it, I'd do what HouseMouse mentioned and use the block heater or keep it in a garage.
I've had first hand experience with 15w40 and low temps which caused some bearing issues and put metal shavings into the oil. When the temps get under 20 (like 10 or below) and the engine is cold soaked, it puts undo strain on the oil pump and the bearings. The stuff will get very thick, which is difficult to pump and can starve the bearings.
I switched to 5w40 Rotella T6 for cold weather (and towing) specifically due to this. I can run it 365 and not have to worry.
I'm not saying you will run into issues, but I'd use the block heater or keep it warm and not let it sit too long in the cold weather until you can change the oil.
just my .02

 

Yeah 12-15 above zero. And that was the temp for only a couple starts in the morning if even that low. As the day went on the temps were consistently above 30. I took it to the dealer and asked for 5w-40 full synthetic but found they used 10-30. I complained and they reimbursed me. Debating on whether to change it to 5-40 full syn. It's not common but we can get some sub zero mornings here.

 

You are fine. We ran 15-40 in all the big trucks year round with low temps down to -40F!!

 

And here I was worried about the factory oil and went to 5W-40...

Personal choice - I like 5W-40 for the reason L3dFord stated. I can run it 365 and in almost any climate and my OCD mind doesn't worry. Since Alaska dealer use the 10w-30 here my OCD mind is a little more at ease. They don't even try the upsell when you get your oil changed.

Best defense against engine wear that you have besides the block heater is waiting for the coil (wait to start light) to go out before starting. Sometimes I will cycle the key a few times. I know the plug still run after the light goes out - but I don't know how long without the engine running. Seems to make starting easier on things.

Also letting it idle for up to a minute and being easy on it for the first mile are not bad ideas either. IMHO, no need for a 5 minute idle for engine purposes. What I notice in the really cold temps (sub zero) is after a couple of minutes, you are not gaining engine oil or coolant heat. It does help the interior cabin temp and the defrosters work though.

 

I'm certain that being 5-7 degrees below the recommended operating temperature that your engine is just fine. I wouldn't loose a minutes sleep.

 

Cold temperature viscosity of 10W30 vs 5W40 are very similar.

 

I agree with the consensus, you're not going to hurt anything with only occasional temps below 20*. Thinner oil makes it easy for the engine to crank, but there are lots of diesel engines that run year-round with 15w40. Just like Troy said above, don't lose a minute's sleep over this.

Just wanted to point out that the glow plugs aren't gonna do a thing for engine wear. Powerstroke engines are about 1,000 lbs of iron and steel...the oil pan, sump, main bearings, crank bearings, rod bearings, and even all the way up to the rocker arms aren't going to care about a tiny glow plug at the top of the combustion chamber. In a 6.7L engine they hit 1,200 degrees in less than a second, but you would burn them out 100 times over before you provided any meaningful heat to the rest of the engine. Their job is to heat the combustion chamber to aid ignition and that's it...doesn't do a thing for the wear components in the engine. It makes the engine fire off quicker and smoother, but the bearings just aren't gonna care.

 

The company I worked for used "year around "in our whole fleet (cars, semi trucks, pickups ) Delo 15/40 for years with no problems in eastern Wa . It gets below 0 degrees at times here .I used Delo 15/40 in my 2011 for 100,000 miles and never had a problem. I do park in a heated garage at night though.

 

Same here... use 15-40 in below 0 temps all the time.. use remote starter to let it warm up first.. 200k on 6.7's and not one issue...

 

I would almost guess that the op's actual oil temp on those few cold mornings was above 20F in the oil pan.

 

My view differs from most on this thread.

No, you won't see an imediatly broken engine from using the wrong grade oil for the ambient temps you're operating in.

Its a cumulative affect. The thicker oil takes longer to get pumped thru the oil galleries and to the bearings and moving parts. Premature wear will take place during these periods. The colder it is the longer it takes and the more wear that takes place.
Now if you use 15-40 dino oil at -25° cold start (its then thick like honey) and won't pump well/fast at all, then maybe you might have a bearing failure sooner than latter. Diffidently more wear than if using the recommended oil.

Also, remember, for the past decade or so, full synthetic oil of the same grade flows much better at cold temps than the same weight dino oil. The oil 'grades' only mean the oil passed the test that allow it to be graded 10-30 or 5-40. It doesn't mean they can't surpass those requirements, and modern day synthetic oils almost always surpass all the testing requirements that dino oils just barely pass...
Most synthetic oils flow cold like **** and protect/pass all the tests hot like a 40w oil. Dino oils can't do this. Synthetic oil can't be beat for the least cold start wear...

jmo

 

You are correct in your thinking.....but the OP was worried about cold start for 2 or 3 days at 10 to 20 degrees. I don't think he will have any issues!
And BTW, I personally use 5W-40 full synthetic myself because I believe it to be superior to 15-40 dino, but I wouldn't run out and change from dino to synthetic for the reasons he posted unless I was close to due for an oil change and wanted to switch.