Convetional 15w40 vs Synthetic?

.
Most synthetic oils are just "reformulated" from conventional oil, they are not "true synthetic". They will call it synthetic base , but it's just reprocessed conventional oil with additives. This doesn't go for all manufacturers though, some actually do create a full synthetic base. But I know Shell/Penz/Valvoline are all conventional base with additives- And based on percentages of additive can legally be sold as "full synthetic" or "synthetic blend".

 

I can't find the temp chart from cat... Don't care that much

But yes I switched from 15W-40 to lighter (synthetic) grade T6 . Because on a cold start I blew the clean gas recir valve . Cat refused to warranty it......

I know they are saying to use 10-30 in the C-15 . Just thought there was a upper ambient temp of like 80 ish .....

 

Well, that is true on its face, but doesn't really mean much anymore. Group III (so-called fake synthetics) not only provide virtually the same level of performance as Group IV PAO synthetics, they actually have some characteristics that are superior to "true" synthetics. Like additive solubility for one. Only the "purists" in the crowd really concern themselves anymore with the fake synthetic vs true synthetic debates of yesteryear.

Here is a good article that expounds on that.

http://machinerylubrication.com/Read/533/base-oil-trends

 

Interesting read for this newbie...

So a few basic newbie questions:

1.) How does one test the oil? I know, or think I do, that one must send it in to be tested. But like how much oil is required and from where does one take the sample?

2.) What is an "oil bypass filter"? What does it bypass? Does it come on the truck or some kind of after market kit? What does it do for you?

3.) How does one track the hours on a truck? Is this done "on" the truck or are you just manually tracking it by day/week?

4.) Company Driver here so just learning but my company does a PM every 50k, which I assume includes the oil change, but I am not seeing numbers that high from within this thread. Are they just using a synthetic oil for which 50k is acceptable to keep the trucks rolling as much as possible? Or since they trade out trucks every 3 or so years, they are not really worried about getting an extra X miles out of an engine and/or can risk an issue every now and then caused by the higher change ranges they use as compared to an O/O or smaller fleet.

Thanks in advance,
MD

 

I'm just reporting exactly what happened with my motor. Oil pressure at normal operating temp with 15W40 was 65 psi. Switched to 10W30 and it immediately dropped to 60 psi. So at my next OCI I went back to 15W40 and my new normal oil pressure at operating temp was now 60 psi.

A bearing roll in was not required. It was well within spec. But it did bring the psi back to 65 and gave me a warm fuzzy feeling. I have no idea what oil was sampling at the time I wasn't doing samples. A look at the old rod and main bearings was all the evidence we needed that I had just thrown money away for nothing on the new ones.

Did the 10W30 oil cause this immediate 5 psi drop in pressure? I can't really prove it scientifically but I must say it's a funny #### thing that it dropped 5 psi immediately after switching to 10W30.

What do you think about that? Coincidence? I guess anything is possible. Needless to say my experimentation with differing oils is over. 15W40 works just fine. If it ain't broke no need need in fixing it right?

 

1) the have oil sample kits. Kinda like a dot drug test kit. Usually pull oil drain plug and wait a second or two and fill the jar out of the stream...

2) I don't use them.

3) my pos has an hour meter in the dash cluster.

4) It depends on the engine manufacturers oil change intervals. But I'd never go that long ....

 

New trucks the manufacturers are actually recommending 40,000 and 50,000 mile intervals. Bare minimum maintinence. These fleets get rid of them between 300,000-500,000 miles so it's the next schlub that will be dealing with all the issues cropping up. Probably lengthy OCI's will be the least of their worries though. More likely they will be spending several $10's of thousands of dollars replacing burnt out, plugged up, used up emissions systems - never mind an inframe.

 

I often wondered this same thing but oil temp does not always go hand and hand with coolant temp. My diesel pickup has a digital oil temp gauge. In 30-40 degree winter temps it is quite a bit cooler than when it is 100 degrees out. Even on long drives when the engine is at operating temp. I don't remember the exact numbers but it was a 30 degree difference if I recall correctly. Not sure if this is significant enough to matter in the 10w30 vs 15w40 debate but the oil temp is definitely cooler in the winter vs 100 degree plus ambient temps.

 

It makes sense that, say, a 10w30 would have a little lower PSI than a 15w40. It is akin to moving milk vs moving molasses, though not that severe of a difference. Which would be easier for you to squeeze thru a plastic bottle with a small opening... water or honey? The 10w30 is not going to generate the same PSI as a heavier oil simply because it flows easier. Pressure is a measure of resistance to the flow. I don't have near the 5 PSI difference between them on my Detroit, but while typical 15w40 would have 49-50 PSI, the 10w30 has around 47-48. And since a lighter viscosity oil does flow easier, it is perceivable that it is getting into the tighter areas like cam and rod bearings a little easier and quicker as well. And the more volume of oil that can get in and thru those areas, the better.

True enough, temps generally will hang around the same as water temps, but can be off somewhat under differing conditions, i.e. a little cooler than the water temp in winter and a little warmer in the summer. And I would contend it really doesn't make that much difference. Most oils, conventional or synthetic, do not reach their burn off flash point till around 450+F, and that is true of a 5w, 10w, 20w, 30w, 40w, or 50w. If the motor oil got that high of a uniform temperature, your motor is toast anyway. I am pretty sure one would already be sitting along the highway long before the oil would fail. And if oil is going to fail running at a temp warmer than the coolant, say, 250F while the engine is at 220F on a hard pull, then Katy bar the door, because the turbo that the oil is flowing thru is at 1000-1200F Yet, the oil does not fall apart and break down after thousands of miles of being run thru the turbo! There is a lot more going on than I think most people take the time to consider. It is a little more dynamic than the little Lucas Oil Stabilizer crank machine at the auto parts counter.

 

I agree 100%. I don't really see anything wrong with 10W30. It is actually what is in my Pete right now because the last service was done at a dealer and that is what they used. Going forward though I will be putting 15W40 in it because I have a drum full of it here at the shop. I have 11 things if my count is right that have diesel engines and I buy oil by the drum because it is slightly cheaper and much easier to deal with. My local dealer I buy the drums from doesn't even stock the 10W30 drums because all his customers use the 15W40. A lot of it likely has to do with the fact that we are in Texas and we see far more hot temps than cold temps. We have a lot of days over 100 degrees and I don't think it got below 20 this winter and there was probably only a handful of times it got below 30.

While I agree that 10W30 isn't going to burn off or have a catastrophic failure at higher ambient temps virtually every manual I have seen for numerous various diesel engines don't recommend it for super hot temps. Some 90 degrees or higher some 100 degrees or higher, etc. I don't know their reasoning but most all of them state that so I will stick to my 15W40. It has worked well for me. Maybe it is just old school thinking I don't know but I have been using it in all my diesels since the mid nineties with good results.