Regular vs Semi vs Synthetic

[BigJohn]

I think nearly every diesel on the road today is topped off with a turbo.

Everyone runs HDEO.

Some run conventional and some run semi-synthetic and some run synthetic.

I want to know if HDEO conventional oils are as good as synthetic.

I read and read VOA and UOA's and it really seems the the likes of Rotella T4 15w40 is about as good as any oil on the market.

What am I supposed to take away from such data? Is $11 a gallon T4 as good as anything?

Should I only be running full synthetic in my Ram EcoDiesel?


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[MParr]

Wouldn’t the same oil that you use in your Mahindra work? Do you see a need to have more than one diesel oil around your house? Rotella T5 15W40 Synthetic Blend is pretty stout.

 

[samven]

I thought Dodge issued a TSB for all year ECO Diesels recommending 5w40 Full Synthetic. They mentioned Rotella 5w40 by name.

 

[Jetronic]

I think nearly every diesel on the road today is topped off with a turbo.

Everyone runs HDEO.

Some run conventional and some run semi-synthetic and some run synthetic.

I want to know if HDEO conventional oils are as good as synthetic.

I read and read VOA and UOA's and it really seems the the likes of Rotella T4 15w40 is about as good as any oil on the market.

What am I supposed to take away from such data? Is $11 a gallon T4 as good as anything?

Should I only be running full synthetic in my Ram EcoDiesel?


.....

They are not heavy duty oils, they are oils for heavy duty engines. If you want heavy duty oils typically you need to go to high viscosity synthetics. High viscosity to give protection, synthetic to handle the increased thermal stress.

 

[Snagglefoot]

Didn’t someone just post a 7.3 with 600,000 miles using mostly synthetic HDEO.
I suppose it could have been done with conventional HDEO if someone wants the chime in that they did that.

 

[dnewton3]

I want to know if HDEO conventional oils are as good as synthetic.

Should I only be running full synthetic in my Ram EcoDiesel?


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Your first question isn't well defined ... you need to put limits on your question such that the conditions for use, environment, equipment used, etc are known. There are times when conventional oils do every bit as well as syns, and times when syns would be a better choice.
- extreme temps (below zero F) would present challenges where syns could have an advantage
- greatly extended OCIs also present challenges where syns could have an advantage
"Normal" use of a light duty diesel truck is very different relative to other off-road service engines. I've seen the majority of UOAs demonstrate that conventional lubes used in a typical OCI have no disadvantage to their more expensive choices. I've personally run many UOAs on my 6.6L Dmax with dino Rotella 10w-30 with very hard use and the wear rates are no worse than guys running 5w-40 syns in similar applications. The success or failure of UOAs and wear rates are as much a factor of the design of the engine lube system more than the oil chosen. Some diesel engine are just well engineered and made, and they really are not picky at all what is used as long as it's a properly spec'd oil for the application. Other diesel engines seem to be finicky and do better with certain grades and base stocks. Because your Q is so vague, the answer is simply "In Depends ..."

Your second question is easily answered. Do you feel compelled to follow the OEM prescription due to warranty concerns? If so, Id stick with what they spec. If not, then there are options outside of that OEM choice that still will do quite well. The real way to know is to understand how the general engine species does in overall UOA macro data, and then get a few UOAs done of your own engine with different oil choices and see how they stack up to the typical standard performance of the general population. It is a false idea to think you can prove what is "better" with small sample sets, but what you can discern is whether or not your engine and lube choices are "normal" or not.

I can tell you from doing statistical analysis on (quite literally) over 20k UOAs of all manner of engines and lubes, syns generally don't provide a good ROI in the typical BITOGers garage because the OCIs are too short (and the operating conditions are not stressful enough) to bring out any clear distinction in wear data results, comparing syns to semi's to dinos.