Synthetic oil: Diesel mechanic says no

[Jeremy5848]

THE FIRST THREE owners of our '96 E300D (OM606NA) used 15W-40 dino oil and drove the car a total of 248,000 miles. When we got it (4th owners) the engine was switched to Mobil-1 5W-40 Synthetic. In 30,000 miles (oil/filter changed once a year or about 7500 miles) the engine has neither leaked nor burned any oil. In November the car will have its 4th oil/filter change since we got it. When I pulled the valve cover to check for timing chain stretch and other forms of wear the moving bits looked almost new.

OTOH, I put Mobil-1 synthetic transmission fluid in the transmission and exacerbated an existing front pump seal leak. The leak went from an occasional drip that could be ignored (and had been by all of the owners since the 100,000 mile point) to a puddle under the car whenever it was driven. I ended up having to get the transmission rebuilt, making it my most expensive oil change.

BOTTOM LINE is that synthetic is a better oil in many ways but its molecules are smaller and can get out of places where dino oil can't. That's why you need to use caution before switching an old anything to synthetic oil. Look before you leap!

Jeremy

[1975300D]

My dad put synthetic once into his W115 and he said it ran terribly. Didn't complain of leaks, but he quickly switched it back out.

[sixto]

Originally Posted by Jeremy5848

THE FIRST THREE owners of our '96 E300D (OM606NA) used 15W-40 dino oil and drove the car a total of 248,000 miles. When we got it (4th owners) the engine was switched to Mobil-1 5W-40 Synthetic. In 30,000 miles (oil/filter changed once a year or about 7500 miles) the engine has neither leaked nor burned any oil. In November the car will have its 4th oil/filter change since we got it. When I pulled the valve cover to check for timing chain stretch and other forms of wear the moving bits looked almost new.

Hardly an indictment of dino unless you're suggesting synthetic put the chain back in spec

Sixto
87 300D

[Matt L]

It's the "looking like new" part that matters. Mobil 1 will clean the brown gunk off of everything, leaving shiny clean metal.

[weird beard]

Conventional and synthetic oils are both fine to use. From my understanding, and talking to oil reps, the synthetic will last longer as the additives will not burn off as fast as conventional. The additives were explained to me by picturing them as beach balls, marbles, ping pong balls etc. The smaller additives protect the tightest fitting parts that the larger ones will not fit in to, however they are lost through looser fitting parts such as piston rings. As the oil is used, you loose more and more of your marbles (no pun intended). Synthetics are "better" oils because the size ranges of the additives are more precisely controlled.

My opinion is the price difference does not warrant the additional protection. The oil still gets dirty. Diesel oil has a high detergent level. It is designed to get dirty. As long as you change your conventional oil before the additives are depleated, you will get the same protection.

You can tune in your oil change intervals by getting an oil analysis done. You may see that your engine pollutes the oil sooner than the oil additives are depleated. Large truck fleets have all experimented with extended drain intervals by using synthetics. My observation is that they all stay with conventional. The oil analysis done on the fleet showed no financial gain using synthetics.

I just use a quality conventional and change it frequently. If you want better protection, use a quality filter. Install a centrifugal filter. It will probably do more for your engine by just keeping the oil cleaner.

I would use synthetics on all other components though as they are not serviced as frequently and the cost difference over time is small.

[ForcedInduction]

Originally Posted by benedict

Diesel mechanic (of some 30 years) says that an engine over 100,000km/60,000miles should stick with mineral.

Thats why hes a mechanic and not a technician.

Should I stick with the mineral oil (currently using 10w/40)? or move to synthetic and hope for the best?

There is absolutely no reason to use dino oil in a maintained engine. Both of my engines have 250k+ with no leaks.

[layback40]

Originally Posted by ForcedInduction

Thats why hes a mechanic and not a technician.


There is absolutely no reason to use dino oil in a maintained engine. Both of my engines have 250k+ with no leaks.

Welcome back Forced !! It was starting to get very quiet here.

I was starting to think we had another "oil thread" developing.

You summed up things perfectly !!!

ALSO
There is no reason to add snake oil to your oil either. The oil manufacture adds all that is needed for you.

[freesoul]

My car went 18K miles on its last change of 5w40 AMSOIL. Testing by AMSOIL rep and filter changes every 4-7K miles. Running mostly B100 homebrew

[vstech]

Originally Posted by freesoul

My car went 18K miles on its last change of 5w40 AMSOIL. Testing by AMSOIL rep and filter changes every 4-7K miles. Running mostly B100 homebrew

... a 95 non turbo diesel engine certainly has a lighter soot load than a 617 turbo, but WOW 18K. I'd think the soot load would be murder at that mileage.
what is the analysis on the oil at that point?
filters are not going to get much soot out, so 4 to 7K filter changes isn't helping much. how much oil are you adding in when the filter is removed? 1/2 quart?
are you using a bypass filter on the car?

[layback40]

Originally Posted by vstech

... a 95 non turbo diesel engine certainly has a lighter soot load than a 617 turbo, but WOW 18K. I'd think the soot load would be murder at that mileage.
what is the analysis on the oil at that point?
filters are not going to get much soot out, so 4 to 7K filter changes isn't helping much. how much oil are you adding in when the filter is removed? 1/2 quart?
are you using a bypass filter on the car?

Also how was the viscosity holding up ? At that mileage you would expect the oil to be like water once it got hot !!

[freesoul]

I'll try to find the last report and post it up

[Zacharias]

Originally Posted by freesoul

My car went 18K miles on its last change of 5w40 AMSOIL. Testing by AMSOIL rep and filter changes every 4-7K miles. Running mostly B100 homebrew

I have heard before that there are quite a few people running well over 10k on Amsoil in the VW TDi community... but I understood that could only be done with secondary filtration setups installed.

[75Sv1]

Originally Posted by ForcedInduction

Thats why hes a mechanic and not a technician.


There is absolutely no reason to use dino oil in a maintained engine. Both of my engines have 250k+ with no leaks.

I would guess 'maintianed' as a good running engine with some milage. I can think of two reason were synthetic might not work as well. First is for break in oil. The next might be for cost, when the car is under warranty. There are specific milages during that time that you must record your oil changes. They vary from car and manufacture. I think 5K to 7.5K. So, if a conventional oil will last in that interval, then there would be some savings.
Now, I am a big fan of synthetic oils. I do notice a few mpg gains with its use. I also think engines and other mechanicals last longer. I do think that conventionals have closed the gap though. I did have a '96 Contour. I had it from 20K to 214K. I ran on synthetics during almost all that time. It was still running, and didn't lose much if any oil in 7.5K oil changes. I think I went 10K to 12K a few times. As far as I know that car is still on the road. That was with Castrol Syntech. I changed to Pennsoil Platinum in the fast 5 years or so. I think 150K-180K with that car.
Tom

[ForcedInduction]

Originally Posted by 75Sv1

I would guess 'maintianed' as a good running engine with some milage.

"Maintained" means at least some amount of preventive maintenance like planned oil changes, valve adjustments and no major oil leaks. If you pop the hood and the engine is filthy, its not maintained.

I can think of two reason were synthetic might not work as well. First is for break in oil.

Thats an old myth that doesn't apply anymore. All modern engines use synthetic from day 1.

The next might be for cost, when the car is under warranty.

There is no cost savings when using dino oil except the per-oil change purchase price. The number of which are greatly reduced with synthetic.
Over 100k miles
$1.50/qt, $10 filter and 3k miles= $683
$6.25/qt, $10 filter and 8k miles= $671

So even though the oil costs 4x as much at the point of sale, over time its cheaper. It also doesn't factor in the amount of time saved doing 13 oil changes instead of 34.
If you pay to have your oil changed, you can bump the figures up to $1363 and $931, a much more drastic savings.

Think of it like having a 16 gallon fuel tank on a car that gets 20mpg compared to a 21gallon tank on a car that gets 25mpg. You're paying less per fillup so to the casual driver it appears like they're spending less money, but over time they're still spending more.

That was with Castrol Syntech.

Thats one of those "group III" fake synthetics. In fact its THE fake synthetic that made Mobil file a complaint with the Better Business Bureau. BBB's poor understanding of the subject made them rule in favor of Castrol's false advertizing and opened the door for others like Shell to do the same.
FYI, after being exposed as non-synthetic Castrol was asked if they would lower their prices because they were using cheaper oil, they flat out said "No."

[otto huber]

[/QUOTE]
Thats one of those "group III" fake synthetics. In fact its THE fake synthetic that made Mobil file a complaint with the Better Business Bureau. BBB's poor understanding of the subject made them rule in favor of Castrol's false advertizing and opened the door for others like Shell to do the same.
FYI, after being exposed as non-synthetic Castrol was asked if they would lower their prices because they were using cheaper oil, they flat out said "No." [/QUOTE]



Just to make this a full blown, cut throat, no holds barred oil thread, are you saying that Rotella T6 is fake?