Everywhere I read a recommendation for OCI in diesel vs. gas engines, the diesels are always recommended to be changed a good 10-15,000 KM later than the gas. And I thought diesel engines are much more efficient and that diesel fuel in and of itself has lubricating properties, much like leaded fuel back in the day contributing to the ease on the oil. They are "dirtier" but any modern synthetic oil that has a B3/B4 rating and CH should take care of that.
How come everyone on here says diesel engines are harder on oil than gas?
- Thread starter HardCharger
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Soot,Sulfur,compression ratio's,total yearly fuel volume,long idle times, turbo charger, loading, valvetrain loads etc.....
The reason that they can go so long between oil changes is primarly a combination of the additive levels in the oil, bypass filtration, constant top ups due to consuption, and the huge volume of oil they hold in their sump!
The reason that they can go so long between oil changes is primarly a combination of the additive levels in the oil, bypass filtration, constant top ups due to consuption, and the huge volume of oil they hold in their sump!
Hmm, interesting. But why does the same oil used for a car (the additives you mentioned are used in both petrol and diesel engine oil) need to be changed thousands of miles earlier? Other than the theoretical consumption which leads to adding oil in between changes and such, which manufacturers can't guarantee since all cars will consume oil at different rates. Do all diesels have by-pass filtration? Does a comparable diesel car (VW Golf TDI vs. 1.8T) have a much larger oil capacity?
fuel water dillution...
higher revs...
?
higher revs...
?
Actually one needs to distinguish OTR diesels vs. automotive diesels as Hardcharger is alluding to - because the driving styles are so much different.
Now for automotive diesel applications - diesels do have less water, less rich on start up, different blow by gasses (main reason), lower revs, different heat cycles, different valve train, -
What JB is referring to (I think) diesel oils are heavier duty, therefore longer OCI.
Now for automotive diesel applications - diesels do have less water, less rich on start up, different blow by gasses (main reason), lower revs, different heat cycles, different valve train, -
What JB is referring to (I think) diesel oils are heavier duty, therefore longer OCI.
Hi,
Hardcharger - IMHE and usually HDEOs don't need to be changed as early as they are when used in many petrol engine families
Oil consumption may well be the same in comparative engines
Sump capacity plays a role but this largely depends on the design philosophy of the engine's maker
By and large and with the exception of some Euro heavy trucks makers, only about 3-4% of heavy trucks use by-pass filtration (I do - a Mann-Hummel centrifuge type)
Without going into some greater depth John's comments are "on the money"
Regards
Doug
Hardcharger - IMHE and usually HDEOs don't need to be changed as early as they are when used in many petrol engine families
Oil consumption may well be the same in comparative engines
Sump capacity plays a role but this largely depends on the design philosophy of the engine's maker
By and large and with the exception of some Euro heavy trucks makers, only about 3-4% of heavy trucks use by-pass filtration (I do - a Mann-Hummel centrifuge type)
Without going into some greater depth John's comments are "on the money"
Regards
Doug
10,000 mile oil change intervals on my
1.9 Liter TDI VW
Cruises at 2,700 rpm each day for about two hours total.
High pressure unit injectors driving by camshaft (very hard on oil)
Most acceleration is spirited and engine is driving at engine speeds similar to a gasser.
Oil analysis confirms that 10,000 mile OCI is safe.
1.9 Liter TDI VW
Cruises at 2,700 rpm each day for about two hours total.
High pressure unit injectors driving by camshaft (very hard on oil)
Most acceleration is spirited and engine is driving at engine speeds similar to a gasser.
Oil analysis confirms that 10,000 mile OCI is safe.
Sump size has a lot to do with it too. Our F250 Powerstroke holds 15 qts.
Sump size has a lot to do with it too. Our F250 Powerstroke holds 15 qts.
WOW !!!
I didnt know that a Powerstroke oil sump was that big. Do you use synthetic or dino HDEO ??
WOW !!!
Number one reason is that a diesel is not air throttled like a car engine.
Take a car engine, change the compression ratio from 9:1 to 20:1, floor the throttle, and then restrict the RPM only by the amount of fuel you inject. Wallah, you just created a diesel.
Because of this stress the bottom end of a diesel motor is ALOT heavier duty than a similiar car engine. Also the parts are now alot heavier as well, which then means the engine is designed (cammed and ported) for lower RPM duty only.
A diesel does not make vacuum at any time, so the ring packs do not clean with downshifting like a gas engine either.
Very interesting. So I am still slightly confused. All the examples I've been shown explain how a diesel engine is harder on the oil. Yet I still don't understand why they recommend nearly twice as long OCI's as compared to gas engines. The oil that is recommended for a gas car is usually the same oil recommended diesel car. And it was said only a small percentage of diesels have bypass filtration. So is it the main reason because they rev so low usually? There are some new "high performance" diesels out now that can rev fairly well. Eg: the new Audi/VW 2.0TDI. BTW, when you say the pistons don't "clean w/ downshifting", do you mean on the downstroke or downshifting a gear?
I think your answer got buried.
Bottom line:
1) Diesels have less harmful and more even blow by (good summary by nickm!!)
2) Diesels are heavy duty and turn slower (mentioned by many)
3) Diesels have larger sumps.
4) Diesels have HD oil designed to match and last.
Bottom line:
1) Diesels have less harmful and more even blow by (good summary by nickm!!)
2) Diesels are heavy duty and turn slower (mentioned by many)
3) Diesels have larger sumps.
4) Diesels have HD oil designed to match and last.
My 1982 Mercedes diesel reccommends 5000mi OCI. Similar gas engine Mercedes have a much longer OCI. I think diesels with oiling systems comprable to a gas motor a need shorter OCI. However most diesels have about twice the oil and filter capacity.
Commercial diesel engines run under continual heavy loads and often in off-road conditions. The first generation IDI diesels did generate lots of soot and acids in the oil. So in those specific cases, the diesels were tougher on the oil.
By contrast, modern TDI (turbocharged direct injection) diesels - both Common Rail and "Pumpe Duese" designs - burn very clean. In addition, their very low specific fuel consumption also contaminates the oil at a slower rate. Furthermore, their significantly lower Exhaust Gas Temps (EGT's) means that TDI diesels degrade the oil much slower than turbocharged gas engines. Finally, #2 diesel fuel (esp biodiesel - which is an ester) has excellent lubricating properties. So fuel dilution is not as harmful as it is with more volatile fuels such as gasoline, alcohol, etc....
Tooslick
By contrast, modern TDI (turbocharged direct injection) diesels - both Common Rail and "Pumpe Duese" designs - burn very clean. In addition, their very low specific fuel consumption also contaminates the oil at a slower rate. Furthermore, their significantly lower Exhaust Gas Temps (EGT's) means that TDI diesels degrade the oil much slower than turbocharged gas engines. Finally, #2 diesel fuel (esp biodiesel - which is an ester) has excellent lubricating properties. So fuel dilution is not as harmful as it is with more volatile fuels such as gasoline, alcohol, etc....
Tooslick
Yah, I decided to stay away from the engine design points. I figured it might get too confuseing. I think a lot of people do not understand how rigid the block and internals are on a comerical diesel as compared to a light duty petrol engine!
Yep, it do hold 15 qts. Do not overfill this one!! With a drain and filter change you don't get 100%, so be careful or you could cause a "foaming" issue.quote:
Originally posted by LT4 Vette:
Sump size has a lot to do with it too. Our F250 Powerstroke holds 15 qts.
WOW !!!I didnt know that a Powerstroke oil sump was that big. Do you use synthetic or dino HDEO ??
We just use Delvac 1300S or Rotella.
I see more diesel pickups than other types of passenger vehicles, but maybe it's different in other parts of the country. Most of the current diesels in pickups seem to require CI-4 or CI-4+ oil, which is very different than car oils. Most of the diesels in pickups have large sumps compared to most cars, My Cummins needs about 12 qts for an oil change, and although the newer models have a 7500 oil change interval mine is 3750 miles. Using a PCMO would void warranty and just be plain dumb as they don't have the detergents, soot carrying capability, and anti-wear protection that a HDEO has.
from another thread...
Maybe the cars are different, but the turbo diesel trucks can get EGTs (exhaust gas temperatures) high enough to do damage, like melting pistons. In general people seem to suggest keeping EGTs below 1250 deg F to 1350 deg, and one of the first upgrades is to get an EGT gauge. Some of the high output stock trucks can get close to that when pulling heavy loads up grades, especially with altitude. They can get hot enough that Cummins suggests letting it idle a bit before shutting down after sustained loads, as diesels cool when idling.
from another thread...
Maybe the cars are different, but the turbo diesel trucks can get EGTs (exhaust gas temperatures) high enough to do damage, like melting pistons. In general people seem to suggest keeping EGTs below 1250 deg F to 1350 deg, and one of the first upgrades is to get an EGT gauge. Some of the high output stock trucks can get close to that when pulling heavy loads up grades, especially with altitude. They can get hot enough that Cummins suggests letting it idle a bit before shutting down after sustained loads, as diesels cool when idling.
That about #2 used to be true but is no longer with the process to remove sulfur, and will be even more so in the near future with the coming of Ultra Low Sulfur Diesel. Now refiners/distributors are supposed to add back in lubricity adds to make up for what they take out, but I do not trust them 100% of the time and is why I and many add supplements to every tank of fuel and why I have been experimenting with every different one I can find to settle on the regimen I like best so I will be prepared for ULSD. Biodiesel is better in this respect but is not readily available.
I realize car and truck diesel engines will be somewhat different in their applications and so forth. A Dodge pickup diesel that is going to be used commercially will be different than a 2.0TDI VW engine found in a jetta. I see your point, though.
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