Dump Rotella T6 and use Delvac?
 

I religiously change oil every 6 months or 5,000 miles. In my W115 I go 6 months for 3,000 miles because of the age of and mileage of the car.

Anyway, I generally don't hit 3,000 miles in a 6 month time frame, so it comes down to time being the limiting factor.

I'm not sure what sort of oil the PO used, but I swapped it out for Rotella T6 5W 40. As time passed I started to develop leaks at the front and rear seals. Also, oil consumption increased. I understand there's a lot of urban myths about synthetic vs dyno. I don't want to go there. Besides, I'm not going to say that it was the oil's fault. The PO rarely drove the car whereas I'm averaging 5,000k/year. Those nagging issues were probably waiting for a serious driver to come along before their reared their ugly heads.

Anyway, I noticed that Delvac 15w40 is half the price of Rotella T6 today. Since I'm not going to see the full, long life benefits of synthetic, I'm thinking about switching to the Delvac.

Any thoughts or concerns?

Dave, do you experience winter where you operate the car(s)?

I have also had leaks with synthetic oil. The tale I was told is that the synthetic oil molecules do not form into the long chains typical of natural hydrocarbons and consequently can get out of small gaps in seals, etc., that block the non-synthetics. (This probably also gives them their cold-flow properties.)

Letting a car sit is probably the worst thing you can do (not your fault, obviously) for seals. They take a 'set' and won't seal properly, especially if they are as old as the seals in your '74 may be.

If you don't need synthetic for cold weather and you're not a high-mileage driver, you might as well go back to Delvac or whatever good traditional oil you prefer. I'll also be interested to hear what happens to your leak if you go off synthetic oil.

Jeremy

HMMM....I went to a synthetic 15-40 in the 240D at 321K, and we are now up to 347K. The engine wasn`t leaking before the switch, or is it leaking now. we got the car as it just turned 306K, and I have no prior maintenance before we got it.

My oil consumption hasn`t changed much from before we went to a synthetic.

Synthetic oil won`t cause a leak, if you have old seals and have been using regular oil, the synthetic will clean out the old gunk etc... that may have been plugging up cracks etc.... in the seals.

There are a ton of old wives tales floating around, just grab one you believe in.:D


Charlie

Answer
 

#1. Stop changing oil by calendar, unless you are in an extreme condensation area.
#2. Stop changing oil at 3000 miles.

3,000 mile myth - Wikipedia, the free encyclopedia
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Busting Oil Change Myth - YouTube
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HowStuffWorks "Do you have to change the oil every 3000 miles?"
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Stop Changing the Oil Every 3,000 Miles Already! | TIME.com
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Stop Changing Your Oil! - Edmunds.com
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http://www.nytimes.com/2010/09/11/your-money/11shortcuts.html?pagewanted=all&_r=0
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Changing car oil every 3,000 miles no longer needed

All modern oil is superior to 1970s - 1980's and earlier.

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Yes, we do. The car is garaged and it only goes out on warm, sunny days when. I don't drive it around town and avoid stop and go traffic/short drives.

I realize that syn offers better cold start up protection but it isn't that necessary for me.

I've done the switch in other, high mileage cars as well without issues. I actually use Mobile 1 in our other 3 cars.


I didn't want this to be another dyno vs synthetic debate which is why I mentioned old vs new driving habits as the primary suspected culprit.


So long as no one can provide evidence to the contrary I'll probably switch to Delvac for the cost savings alone. But if there is some improvement (doubtful), I'll be sure to post back.

Not to add fuel to the fire, but if I'm experiencing blow by wouldn't soot loading be a concern and cause the oil to become "contaminated", for lack of a better word, before it's time?

I know that I can extend the linterval for syn oil, but without testing the oil every few thousand miles the only indicator that I have to go on is the color of the oil. Color = nasty.

I believe Mobil 1 specifically says in its tech or marketing materials that it will not worsen any existing leak (they started saying that in the early 2000s, after a reformulation, it was not always their claim). As far as I know, no other synthetic says that.

I ran it in a really pooched, high-mileage Volvo 740 Turbo that both leaked and burned oil -- a model notorious for oil leaks and crankcase pressurization issues -- and I can confirm if anything it leaked LESS on Mobil 1.

I was under the impression that the "3,000 miles myth" applied only to gassers. I thought 3,000-4,000 was still preferable on diesels, due to soot concerns.

Answer
 

Color is useless, typically it changes in seconds or hours of running.
Your blow-by would need to be pretty spectacular to load the oil to a serious level in less than 5000 miles.

I test the oil when I get the vehicle (fresh oil change), at 6000 and 9000 miles, then decide what interval.

Thus far all of mine are 9000 mile oil changes, even though the test says it is not required for at least another 3000 miles, simply because I don't choose to push it further and feel better knowing it has reserve life if mechanical issues do occur.

For myself, it is cost effective at 9000 mile intervals to run synthetic oil.
Currently I re-test each engine once every 2-4 years depending on miles driven.

Blackstone Labs

Oil Analysis Kit - MyPilotStore.com

Engine Oil Analysis - Bob is the Oil Guy

HowStuffWorks "Engine Oil Analysis Kits"

Four Lethal Diesel Engine Oil Contaminants

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How often do you change the filter?

I have a Jeep engine that has leaked oil three seperate times on synthetic oil. Every time, I switched back to conventional oil at the next oil change and the leaks stopped. I am pretty convinced that synthetic oil will leak where conventional oil will not. If the "cause" of the leaks was "cleaned out old gunk," the conventional oil must have plugged the gaps pretty quickly.

What's the soot level at 9000 on a 617?

Do you go 9000 on the filter?

My own decision is 5000 based upon a 1% soot limit. Apparently you are OK with higher?

Answer
 

The critical factor for me is any engine coolant in the oil, that kills more engines than soot ever will.
By the time you see coolant (milkshake) discolored oil, it is usually a major engine and injection pump rebuild.


You are correct, I have run considerably higher, typically, the suggested limit for soot on the old mechanical injection diesel engines was 3-5%.

On my personal vehicles 2% soot with 0W-40 synthetic oil is simply indicating oil change needed now.

At 9000 miles my worst engine is 1.5%, the others vary between 0.5% and 1% soot load.

Please note that:
* I tune to the lean side for durability/MPG.
* Due to serious low diesel cetane issues I add 4-6 ounces of two stroke oil in every tank of fuel.
* Due to serious random fuel quality issues Biobor and StarTron are required frequently (more than 4 times per year).

The filters are changed every 3000 miles, they are cheap and easy.
If during engine service I suspect contamination, the oil is changed regardless of miles.
This is all a matter of choice to me.

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Looking at the numbers it's fairly easy to do a simple cost analysis for synthetic vs conventional oil. Rotella synthetic at $27.99 / gallon is about 55% higher than Delvac at $17.99. Increasing the drain interval by 55% to offset the cost means changing oil at 7750 miles instead of 5k, easily achieved by synthetics in most diesels. If we accept that most operating conditions for our engines do not require any other special advantages offered by synthetic oil then we've kept the lifetime cost of oil the same while achieving fewer oil changes.

But I often have a different take when asked about switching to synthetics. In this area we have high humidity, high winter salt usage, and some very rough roads. From this tech's perspective the cost of extended drain intervals on older vehicles in this market seems to be more surprise repairs involving more work and larger shop tickets. I counter the argument to spend more on synthetics by suggesting that using the oil change as a chance to check the car front to back means you're more likely to catch problems before they become major issues. If a DIY person feels there's a correlation between spending money and improving the perceived level of protection I'll recommend reducing drain intervals by 10%, staying with conventional oil, and dedicating an extra 1/2 hr with each oil change to inspecting other areas of the car. With poor quality replacement parts flooding the market I sometimes feel like I should be checking for problems weekly anyway.

Oil analysis is inexpensive and easy and can help you get much more than warm fuzzies from your maintenance program.

Thanks.

It really begs the question, that is not possible to answer without much more data, regarding the wear caused by soot. If 1% soot causes a specific level of wear, will the wear be double that amount with 2% soot?

It's a rhetorical question as I do not believe anyone has a good answer for it.

I agree completely about the coolant contamination in the oil. That's the kiss of death.

There are lots of interesting studies out there that try to address Brian's rhetorical question. For instance, Google Scholar came up with the document below. Full copies are not available for free unfortunately. Two highlights from the abstract which many here will hopefully appreciate: 1) EGR accelerates wear on diesel engines and 2) wear increases proportionally to soot loading in the oil.

Sato, H., Tokuoka, N., Yamamoto, H., and Sasaki, M., "Study on Wear Mechanism by Soot Contaminated in Engine Oil (First Report: Relation Between Characteristics of Used Oil and Wear)," SAE Technical Paper 1999-01-3573, 1999, doi:10.4271/1999-01-3573.

Abstract:

Increase of soot contaminated in engine oil caused by EGR system accelerates the diesel engine wear, especially in the valve train. Wear of metal is affected by many factors such as concentration and diameter of soot, oil film thickness, oil characteristics, etc. Effects of soot on metal wear were discussed from the point of view of soot concentration, and soot diameter and oil film thickness. Wear test was carried out by using four-ball wear tester. Consequently, it was made clear that wear increases proportionally to soot concentration, and relation between oil film thickness and soot diameter plays very important role in wear mechanism. Further, the surface of wear scar was observed by SEM to discuss effect of soot diameter on wear and existence of abrasive wear by soot and its occurrence conditions were suggested.

Thanks. I never realized such a document was available and that they confirm a linear relationship between soot and wear.

Almost, but not quite linear
 

BC-
I was able to find a similar document for download via my school library. It is by some reliable folks at WVU. I turned one graph from their pdf file into an image, so I could post it here. It is a bit small, so let me know if you want me to upload a better version. The wear is not quite linear with soot, and I just didn't want to misinform anyone. The reference material is below.

Effect of diesel soot contaminated oil on engine wear
Sam George, Santhosh Balla, Mridul Gautam∗
Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown 26506, USA
Received 28 February 2006; received in revised form 22 September 2006; accepted 13 November 2006
Available online 6 December 2006
Abstract
Contamination of lubricating oil by diesel soot is one of the major causes of increased engine wear, especially with most engine manufacturers
opting for Exhaust Gas Recirculation (EGR) technology to curb oxides of nitrogen (NOx) emissions. The diesel soot interacts with engine oil
and ultimately leads to wear of engine parts. Factors which can change or modify the characteristics of the soot surface are expected to play an
important role in controlling the interactions with soot. Hence, it is important to study the interactions between soot and oil additives in order to
develop high performance diesel engine oils for engines equipped with EGR.
Astatistically designed experimentwas developed to study the effects of soot contaminated engine oil on wear. The variables that were considered
were the base stock (groups I and II), dispersant level, and zinc dithiophosphate (ZDP) level. The above three variables were formulated at two
levels: low (−1) and high (1), which resulted in 23 matrix (8 oil blends). In order to study the non-linear effect of soot, it was considered as a
variable and was tested at three levels: low (−1), medium (0), and high (1). This resulted in testing of 24 oil samples.
A three-body wear machine was used to simulate and estimate the extent of wear quantitatively. The extent of wear was measured as the actual
loss of material, in grams. A second set of experiments were performed on a milling machine (ball-on-flat disk setup). The wear scars formed
on the steel balls were examined using a scanning electron microscope (SEM) and were analyzed qualitatively to determine the effect of soot
contaminated oils on wear.
The results obtained were analyzed using the general linear model (GLM) procedure of the statistical analysis system (SAS) package to determine
the significance of variables on wear. The analysis indicated that wear increased nonlinearly as the amount of soot increased. Cumulative wear
was more for samples with soot contamination than without soot contamination. This showed a detrimental effect of soot on the oil blends wear
performance. The SAS analysis showed that the base stock and soot content were the most significant variables affecting wear. Dispersant and
ZDP levels were also found to be significant. The highest wear resulted from a sample that had 4% soot.

Oh, and sorry for hijacking your thread BPDave. That always seems to happen with an oil-related thread, but it is no excuse.

they had a university study on diesel oil,1 Cummins 5w40,2 rotella15w40,3 rotella 5w40, thats the honest truth
I use Cummins now in both my om617.951 and m104

http://www.peachparts.com/shopforum/...c-sootwear.gif


This graph is rather interesting.


Although the curves are approximately linear, the slope of the curve is quite flat. Using the upper curve, the wear at 1% soot is .0039. The wear at 2% soot is .0044. This represents a 13% increase in wear for a doubling of soot. That's a decent tradeoff, IMHO, and it suggests that running 2% soot as a maximum is hardly detrimental as compared to the traditional 1% limit.

Based upon this data, I'll seriously consider raising my OCI above the current 5K.

Just to add more links as to why Changing Oil Often leads to more engine wear.

Long term UOA test results.
Mobil 1 Test Results


SAE white papers.
The Effect of Oil Drain Interval on Valvetrain Friction and Wear

Antiwear Performance of Low Phosphorus Engine Oils on Tappet Inserts in Motored Sliding Valvetrain Test

Raman Characterization of Anti-Wear Films Formed from Fresh and Aged Engine Oils






3,000 mile oil filter changes are too frequent. I think 61x and 60x filters should be good up to 7,500 to 10,000 miles. But a UOA on the specific engine will tell for sure.


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Hmm
 

It is a personal choice.


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Of course it is.

Some personal choices are well-grounded. And some are not.

very interesting thread…plus all the external references are excellent.

Slightly off topic – what is the general take on using a pre-oil change engine flush?

I use lubro-moly engine flush around once every year. I figure they’re a reputable manufacturer, and reason this makes sense especially with a longer oil change interval.

What do believe you are "flushing" once the oil is drained?

Absolutely agree.

It also has a beneficial effect for Luqui Moly.

DeliveryValve-
I am far from an expert on the subject, but as far as I could tell, some of your links are to studies in gasoline engines. And it may be that conclusions for gas engines are not identical as for diesels, due to soot loading concerns.

On page 5 of this Harley white paper explains why your synthetic leaks occur.


It also gives some background on engine oils.


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The idea that I'm pointing here is that 3,000 mile oil changes are bad for a motor and keeping it as long as you can will provide a benefit. Even though these links are for gassers, the theory behind it is the same for diesels.
Soot over 2% should be a concern. Roy stated earlier, at 9,000 miles, his worst soot load is at 1.5%. Depending on the TBN, this oil still has the potential to go further. But in the end, Roy has his change interval spot on where I think it should be without doing any UOA. Between 8,000-10,000 miles


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Isn't science fun! We have some research papers indicating that increased soot loading increases wear rates in diesel oils, and we have other research papers indicating that wear rates decrease the older the oil is (in gassers). So in review... don't change your oil frequently, and don't change your oil infrequently.

And the reason has nothing to do with gunk, which was my point to begin with.

Actually the best way to do it is not to change it blindly, but to have your oil analyzed by a reputable lab and run it at an interval deemed safe by the report if you are going to run it past the factory recommendations.




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I wonder if the apparent reduction in wear material accumulation over time is not, in fact, a reflection of the oil's inability to maintain said material in suspension.

I don't think that is the case. I could be wrong about this, but this is my understanding of how the oil functions through reading various articles around the net.
Motor oil is produced with an additive package that bonds to the moving parts through the high pressure contact of the said parts. These additives account for like 3% of the volume of engine oil, but produce 90% of the engine's oil protection. With only 3% of volume, these additives need to be continuosly circulated to start bonding to the engine.
Here is an article on bob's the oil guys website about how one additive works, which is similar to the other types.

Moly Basics - Bob is the Oil Guy

When you change oil often, you introduce an initial cleansing detergent. This detergent attacks and cleans out all contaminants from the previous fill. Though it does a great job of cleaning, the drawback is it also cleans off the existing additive bond and prevents the new additives from forming their bond to the moving parts until the detergent cycle is used up during the first 1000 or 2000 miles. This is why when doing an oil analysis, several UOA's has been posted in various forums show the engine oil's wear rate is actually higher at 3,000 miles, then it is at 7,500 mile and at 10,000 miles. By keeping the engine oil in there longer, the detergent cycle is reduce and the additives get a chance to bond longer which leads to less wear on the engine plus with the added benefit of saving a lot of resources and money.


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That is exactly my point. The oil analysis appears to give a false indication of when the wear is actually occurring. The increased dispersant capacity of the fresh oil is giving the impression of "new" wear, when, if fact, the wear particles are remnants of the previous oil cycle. The old oil was just not able to keep the wear particles in suspension.

Your point of residual metals of the previous fill might be valid. I do believe the cleansing refers mostly to removal of organic contaminants like acid, soot, water, etc. than the non-organic contaminants like wear metals. But I would think the lab would be able to trend and identify when the oil becomes saturated and loses it's ability to hold the wear metals. Also, you should be able to tell with a decrease in count of the additives magnesium and calcium that the oil no longer has the ability to remove, hold and suspend the contaminants which would lead to residuals left behind during an oil change.
I would also have to consider the SAE studies that I pointed to earlier to holding a lot if weight in this subject. It is one thing to look at an oil sample, but to get a better point of view, look at the actual parts in questioned for actual wear rates.


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I'm willing to consider evidence showing some properties of oil are improved with age. I'd love to see the actual SAE papers referenced previously. I also think it's fair to claim too frequent oil changes are costly and unnecessary if you can back it up with evidence. But I wonder if extrapolating the test results to claim that too frequent changes are harmful is correct. I'd be very interested in data showing an engine failed prematurely due to too frequent oil changes.

FWIW our fleet vehicles regularly see 300k plus miles on original engines, both diesel and gas, with 3k mile oil changes. It's the bodies, not the engines, that usually take them out of service. If the 3k mile oil drain intervals were detrimental I'd expect to see differences between the bulk of the fleet and our three '04 Sprinters which have drain intervals ranging from 7k to 10k miles depending on oil used.

Answer
 

The science has proven 3k mile oil drain intervals are not detrimental, just environmentally and economically wasteful.

I know many antique/classic vehicle owners still follow the three month calendar oil service = the engine may run 5-15 hours on each oil change, with a much needed rebuild every 10-15 years.
It is debatable whether the lack of running or the excessive oil change do more to cause the required rebuild.


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