Synth vs. Dino: Bottom Line - Contaminents

[TeryT]

Greetings!

Over on the RV.net forum we have hashed this topic out to death on several occasions over the past year. While I think we're all pretty convinced of the merits of using synthetics in our RVs, one question always seems to be left unanswered. And this question would seem to me to be the main determining factor.

Since synths can go longer in an engine without breaking down, what is the contaminent levels after a period of time? Say the synth is left in there for several thousand miles more than a dino, are there the same, more or less harmful contaminents?

I realize that this may be a simplistic question, but I'm also hoping for a simplistic answer from someone. People have posted all kinds of charts, graphs & figures trying to show what's going on, but I'm hoping for the bottom line - and perhaps a link that shows in the simplest terms possible.

Also, as a side bar, where does synth blends fit into the contaminent picture?

BTW - The application for those of us on RV.net is mainly towing vehicles & motorhomes.

Thanks!

 

[buster]

I think as long as your filter, TBN and wear numbers are good or within range, there is no problem. If the Total Base number is depleted, the oil can no longer do it's job and wear metals should sky rocket.

Two scenarios would be:

Dino oil- @ 4k miles Fe - 5ppm
TBN - .5

Synthetic- @ 10k miles Fe- 11ppm
TBN - 4.0

In these two cases, the dino is almost depleted with a TBN of .5. The synthetic has more Fe floating around, but it's not harmful at these levels or even much higher. TBN is still 4.0 showing the oil has plenty of life left. TBN is a good indicator if it's done correctly. I'm not a tribologist but this is how I see based on what I've learned on here.

 

[JohnBrowning]

RV are a different breed all together. THey run hot all the time. It would be in your best intetrest to probably keep to the OEM schedule even with premium synthetics. If you have a GM 454 in it then once the manifolds crack look for some stainless steel big block manifolds. These were factory equipment for big block fleet vechiles. THey are welded tublura stainless steel and cast SS with air fitting for smog and the whole 9 yards. When it is time to rebuild it due to burnt valves or head gasket failure upgrade to the best one piece valve that TRW makes for the exhaust side. They will run 35-45 dollars a pop but they are well worth it. Copper head gaskets and exhaust manifold gaskests are also a good idea.

It is also a good idea to add synthetic oil to the trany and diff. Upgradeing the already large oil and terany cooler is a great help as well. Heat related failures are the most common type of issues for RV's.

If it is a diesel then most of what I discussed above is not an isses!

 

[TeryT]

Thanks for the replies. I keep to a shorter time period in between changes than many might with synthetics - just to be on the safe side. I also run synthetic blends all thru the drive line. My practice has been to extend the changing frequency by about 60% (e.g. 5,000 miles as apposed to 3,000 for engine oil). But I always wonder about the contaminents.

So, I'm really looking for a bottom line kind of analysis. All other things being equal, which would have less contaminents over an equal period of time?

There must be empiricle data out there on this (the the novice like me could understand)!

 

[Pablo]

TeryT - please explain what you mean by "contaminants"....?

Do you mean Si entering the oil via the air intake? If so, this really is not a concern in a normally operating intake system. Even the very long OCI's - 15-20K miles + don't really built up incoming solids or silicon.

As mentioned by others here your main issue will be high temp oxidation. Use a good oil (synthetic) and don't overextend it....

 

[RJCorazza]

Oil contamination during extended OCI's is what got me looking into bypass filters. I believe all but Silicon (?) in an standard oil anaylsis are dissolved (or almost) material ie: iron. Perhaps someone could confirm this. Anyway, there is a test for particulate matter that is used mainly for hydraulic applications. OilGuard has some info on their www site about it.
The TBN seems to be the number to determine an oil's end of service life in most cases. Using a Bypass filter and adding occasional make up oil during filter replacement I hope to keep the oil clean of contaminants as well as keeping the TBN higher for a longer period. I put a sub-micronic filter on a 10 gal hydraulic system and want to have the fluid anaylised (sp) for solids (size and count).

 

[Jimbo]

Assuming that we are talking about gasoline-powered RV's, I think the contaminant issue he is talking about are from the normal blowby, water, soot, unburned and partially burned gas, etc. The argument against synthetics is that these still build up in the oil and are bad, so you cannot do extended changes. The argument for synthetics says that the oil itself is not breaking down and contributing to the problem, and the "premium" additive package can deal with the other stuff.

I would be willing to try extended drains only with oil analyis. So, for the average owner, dino at normal intervals would be the "safe" choice.

The only person I know with an RV drives it only in the summer, so it operates hot, with no winter starting requirements and it is not started for months at a time, so internal corrosion is an issue. It is a carburated Dodge 440. HIs solution, straight SAE 30 Valvoline, changed every fall.

The logic is this. Straight 30 clings to parts better when cold for long term storage. It also has no polymers and a high flash point for excellent high temperature performance. 30 is recommended in the owners manual for summer temperatures.

I am trying to get him use Delo 30 and stop using Fram, but I am not winning that argument. At least they are the white Frams, not the cheap orange ones!

 

[TallPaul]

Here is my UOA for an extended (manual says 3000 miles, I did 4400) oci on my motorhome. It seems to have done quite well, but it was not mid summer heat:
http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=3;t=001575#000000

(Note that the analysis says it thickened to a 40 wt, but a couple folks have seen their 10w30's reported by this lab as 40 wt, so it may be lab error as the oil pressure never went up correspondingly.)

 

[TeryT]

Quote from Jimbo: "Assuming that we are talking about gasoline-powered RV's, I think the contaminant issue he is talking about are from the normal blowby, water, soot, unburned and partially burned gas, etc. The argument against synthetics is that these still build up in the oil and are bad, so you cannot do extended changes. The argument for synthetics says that the oil itself is not breaking down and contributing to the problem, and the "premium" additive package can deal with the other stuff.

I would be willing to try extended drains only with oil analyis. So, for the average owner, dino at normal intervals would be the "safe" choice."

This is pretty much what I am talking about. I don't know about oil analysis, so I was asking a "bottom line" on this question. There must be some definative comparative studies out there that would say that there is a safe level of "bad stuff" (my technical name for oil contaminants) in running synthetics out say, twice as long as dino.

I don't care to know all the oil test jargon (sorry folks), but just feel that someone must have taken two identical vehicles, one with dino & one with synth, ran them hard the same way, and tested every thousand. Everyone knows the synth will last longer (is this the "TBN"?), but is there also less "bad stuff" floating in the oil?

Am I over-simplifying this, or is everyone else making it more complicated than it has to be? LOL (perhaps both?)

Hopefully a novice like me is welcome to sound stupid on here!

Thanks!

[ June 29, 2004, 08:50 PM: Message edited by: TeryT ]

 

[TomJones76]

quote:

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Originally posted by TeryT:
Everyone knows the synth will last longer (is this the "TBN"?), but is there also less "bad stuff" floating in the oil?

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The amount of non-metallic "bad stuff" will be the same in either conventional or synthetic oils at a given mileage.
The amount of metallic (that means stuff that used to be part of your engine) "bad stuff" in your oil will generally be lower in a quality synthetic oil than it will be in a normal conventional oil.
The *difference* between the quantities of "bad stuff" between a good synthetic and a normal conventional probably won't be substantial, or even statistically significant, at 6,000 miles.
The biggest advantage of synthetics really is the fact that they can endure more high-temperature usage.
The second biggest advantage of synthetics is probably that the right synthetic will flow at downright arctic (-40 Fahrenheit) temperatures.