Straight SAE 40 VS. 15W40

Done. Straight SAE 40 is what I'll use! Thanks so much!

 

BUMP..........I'm going to change the oil in a 3406E CAT, Im considering SAE40 instead of 15-40. THE ONLY SIMPLE QUESTION I HAVE Has anybody else tried it? in a 3406E model.

 

There's no advantage to running SAE 40 in any of our diesel motors other than a detroit 2 stroke.

 

even with the oil staying a straight weight?

 

Well it seems not many people understand the w in 15w40.It will make no differance running sae40 over 15w40. The w represents winter so its broke down as follows in cold temps the oil will not get any thicker then a sae 15 oil. As the engine heats up and the oil gets hot the 40 represents that the oil will not be any thinner consistency then a sae40 whieght oil. The only thing you will accomplish running sae 40 is possible oil starvation in cold temps or increased strain on oil system in cold temps.

 

I understand thanks

 

If you want to upgrade, run full synthetic. Rotella 5W40 full synthetic is only $20 per gallon. And after you drain it, you can then use it for hydraulic fluid, and get double the ROI!

 

CF 2 40 is a low detergent oil with wiping properties that favour the ring/ liner action of a always pressured roots scavenged 2stroke Detroit. 15w40 does stick, but the higher detergent contact causes the stickiness to break down faster, Detroit recommended changing oil twice as often when using 15w40 in cold climate, they preffer you to use 30 over 15w40. CF2 40 doesn't have anywhere near the right additive package for a modern 4 turbo charged stroke.

there are a lot of letters between f and j

 

Google is your friend, click on the link for further reading. I just copied the opening part about multi-grade oils. I get what you are saying but you might be over thinking it a little bit.

Copied directly from http://motorcycleinfo.calsci.com/Oils1.html

Making Multi-Grade Oil


A simple standard oil, for example a pure base stock, would be a single weight, like 30 weight. This pure oil would have no detergent additives to keep the engine clean. This oil would be relatively thick and difficult to pour at room temperature, and would thin out as the motor heated up. On a very cold day, say 10° below freezing, this oil would thicken to the point where you could not start your motor, and if you did, the oil pump could not pump the oil around to protect your motor. It used to be that to start their diesel trucks in the winter, truckers would add kerosene to their oil to thin it out. Then they had to hope the kerosene would burn off before it did any real damage. Today, synthetic oils that are rated 0W-40 flow normally down to 65° below zero and remove the need for engine block heaters or adding kerosene.

An oil sold as 10w-40 is no thicker than 10 weight oil under Winter (10w) conditions, meaning below freezing. The 40 means it is no thinner than 40 weight oil at 212° Fahrenheit. So, the first number tells us the performance of the oil at or below the temperature of freezing water, and the second number tells us the performance at the temperature of boiling water. The chemicals added to the oil to accomplish this are called Viscosity Index Improvers (VIIs).

To make a 10w-40 oil, the manufacturer would start out with a 10 weight oil as the base stock. All by itself, this oil would thin out so much at normal operating temperatures that the oil film would be useless. So, they add these very special very long molecules, the VIIs. The VII molecules are as much as 1000 times as long as an oil molecule. The VII molecules curl up in a little ball at room temperature, but as the temperature gets higher they uncurl and stretch out, like a cat sleeping in the sunlight. The more stretched out the molecule is, the more it impedes the normal flow of the oil, thus raising the effective viscosity. Now, this sounds just a little too good to be true. Well, there are two catches: first, these molecules are not lubricants, so the more of them that you add the less oil you have sitting around lubricating things. Secondly, these VII molecules can be broken into pieces by various pressures and forces, like being squeezed through the transmission gears in a motorcycle or the hydraulic valves in a diesel engine. Every time a VII molecule gets broken, the oil loses some of its high temperature viscosity. Synthetic oils made from pure PAOs and/or Diesters typically have very few VIIs, so these oils are far less subject to viscosity breakdown due to shearing of the VII package. As a result, synthetics are far more stable in a motorcycle engine.

10w-30 oil increases its viscosity at high temperatures by a factor of three, which requires a significant amount of these VII molecules. 10w-40 oil increases its high temperature viscosity by a factor of four, which requires even more even longer molecules. 20w-50, which sounds a lot like 10w-40, only increases its high temperature viscosity by a factor of two and a half, so it requires fewer of these molecules than even 10w-30. 15w-40 also increases its high temperature viscosity by about two and a half, so this oil is also substantially more stable than 10w-40. Most passenger car oils today use inexpensive VII molecules that break apart relatively easily. Conversely, most diesel engine oil VIIs are chosen from more expensive chemicals that are more shear stable, since an oil change in a large diesel is expected to last for 15,000 to 150,000 miles.