I agree 100%. Go into a garage when it is 20F or colder. The colder, the worse it gets. Open-up a bottle of 15w-40 conventional. Try and pour it out. It will move like a snail and when it eventually pours out, it will pour like molasses.

Now, do the same, but with synthetic 5w-40. It pours just fine.

There is a REASON why Cummins puts in their manuals, that when it is below 0F, synthetics should be used. The cold starting is what kills the parts. As the wear and tear is tremendous.

 

Synthetic oil has a number of advantages, cold start or no.

Shear and film strength in a real synthetic (like Mobile1) are better than conventional oils. The molecules are produced from a uniform process-something like making pure yarn from dirty whole wool.

Also - in a cold-engine (not attempting to get into cold weather here) situation you get oil to passages, bearing surfaces etc much quicker. -40 or no you still get oil to load-bearing surfaces quicker. Does it matter? I don't know - how many rotations of 22:1 compression on your mains are you comfortable with having unlubricated? My answer is zero but absent that as few as possible. I start my truck 2x / day.

Synthetic oil should also be lower in contaminants and have a higher flash point helping reduce varnish and sludging.

Finally - it doesn't rely on an additive package the way conventional oils do to maintain multi-viscosity characteristics: more of what's in the bottle is made to lubricate and not to change behavior at a specific temperature.

Run what you want: I 100% respect people's opinions: it's your/their money and their rig. I'm just some guy posting on the internet and I have no right whatever to tell you what to put in your rig. My old toyota 2L ran on Delvac for -years- and never, ever had a single mechanical issue (200K miles-respectable for a motor built off a gas-engine block).

Good luck.

 

would my 97 12v be ok to run the 5w40 in I have always run the delvac 1540 wiht good results but can tell when it gets really cold

 

Guys, I've been mixing synthetic and dino 50/50 for many years in both my gassers and my diesels. In my truck now I'm putting in 1 gal Mobil 1 to 2 gal 15W/40s. My thought is, I can add some of the properties of syn to the dino for not as much $, especially at cold start I am hoping it helps. What's your opinions?

 

Doesn't sound like it would hurt anything. I was using 15-40 and changing it every 5000 miles. When I switched to 5-40 synthetic a little over a year ago, I started changing every 10000 instead. Keeps the cost about the same and it cranks over much easier in the winter. There also seems to be a slight increase in mpg.

 

Another advantage for those extending oil change intervals or leaving the truck unused for extended periods is that there is no sulfur in pure synthetic to combine with moisture and produce sulfuric acid that then eats away at internal components. Over time the oil will become contaminated anyway, but initially you start out with a clean slate.

There is something about synthetic that reduces sludge for those engines prone to sludge built up.

 

That thing is at least $120 oil change and that's doing it yourself. My wife and I almsot bought one, but that was a deal breaker for me.