I am looking for some info on why most diesel manufacturer's recommend a 40 wt oil such as 15w40? I am still confused on viscosity a bit.... in regards to gasoline engines nowaday's it seems that anything thicker than a 5w30 is not needed. Before I joined this forum my reasoning for using anything thicker than a xw30 for is if the engine was built "loosly" with large bearing clearances, or if it consumed some oil. I also used to think that a thicker oil would provide a thicker "cushion: between moving parts, but I was informed on this forum that thicker is not always better, as it circulates slower through your engine, and that thinner oil carries away heat better than thick.. etc.... again what is the reasoning for 40 wt oils in diesels?
Someone please explain why xw40 in diesel's?
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Thanks shannow.....but why the high HTHS value? Is it because of the tremendous amount of power these machine's produce? If so...I tried to argue this on a gasoline forum. My argument was that there are alot of gas engines producing tremendous power these days (My truck included 2008 VortecMax 6.0) and why do they still recommend a 5w30?
Lots of torque down low on the diesel engines.
Ponch, that "knock" that you hear in diesels at idle is a tremendous pressure spike that has to be dealt with by the lube. Also, some engines have some pretty extreme pressures in the area of the injector cam (if used).
Crinkles, a lot of the D.I. diesels (particularly the Japanese) are specifying more PCMO like oils these days. My Nissan is supposed to be 10w30, CF-4, Jaso DH-1...if I could get such in Oz.
Crinkles, a lot of the D.I. diesels (particularly the Japanese) are specifying more PCMO like oils these days. My Nissan is supposed to be 10w30, CF-4, Jaso DH-1...if I could get such in Oz.
Diesel engines do not run at as high of RPM to produce the same power. A six litre gasoline engine may produce peak power at 5,000 RPM. A six litre diesel engine may produce peak power at 2,800 rpm.
If both engines produce 350 horsepower, the diesel engine needs nearly twice as much torque (produced by higher cylinder pressures rather than firing more often) to do so because of the lower revs, which means nearly twice as much loading in all of the bearings requiring the film strength of a high HT/HS oil. To qualify for CJ-4, the absolute minimum is 3.5 for a XW-30 and 3.7 for an XW-40. The typical 15w40 is in the 4.2 range, and 150% thicker at high temperatures than the often specified 5W-20 of new cars.
If both engines produce 350 horsepower, the diesel engine needs nearly twice as much torque (produced by higher cylinder pressures rather than firing more often) to do so because of the lower revs, which means nearly twice as much loading in all of the bearings requiring the film strength of a high HT/HS oil. To qualify for CJ-4, the absolute minimum is 3.5 for a XW-30 and 3.7 for an XW-40. The typical 15w40 is in the 4.2 range, and 150% thicker at high temperatures than the often specified 5W-20 of new cars.
The m anual also recommended DLD-1 spec oil. I'd never heard of it, but here is a link.
http://www.enginemanufacturers.org/admin/library/upload/287.pdf
I was really surprised how rough the diesel motor was today - it only has 8000 km on (work vehicle on site)
http://www.enginemanufacturers.org/admin/library/upload/287.pdf
I was really surprised how rough the diesel motor was today - it only has 8000 km on (work vehicle on site)
Diesel engines also cruise/live most of their lives at low rpm. A good friend that drives on of those big semi-tractor, double clutching e flat trailer trucks says running the open road was usually around 1500-1650 rpm. As explained to me by a tribologist, a crankshaft journal pulls the oil supplied by the pump into the bearing to form the protective wedge. The thinner the oil and the lower the rpm, the more difficult to pull into the bearing. At lower rpm the 40 grade oil is easier to pull into the bearing. I know this is probably a poor explanation, but hopefully you get the gist.
This is why I use 15W-50 synthetic in my gasoline engines that rarely, if ever, go over 2000 rpm.
This is why I use 15W-50 synthetic in my gasoline engines that rarely, if ever, go over 2000 rpm.
Originally Posted By: FrankN4
Diesel engines also cruise/live most of their lives at low rpm. A good friend that drives on of those big semi-tractor, double clutching e flat trailer trucks says running the open road was usually around 1500-1650 rpm. As explained to me by a tribologist, a crankshaft journal pulls the oil supplied by the pump into the bearing to form the protective wedge. The thinner the oil and the lower the rpm, the more difficult to pull into the bearing. At lower rpm the 40 grade oil is easier to pull into the bearing. I know this is probably a poor explanation, but hopefully you get the gist.
This is why I use 15W-50 synthetic in my gasoline engines that rarely, if ever, go over 2000 rpm.
My gas Jeep engines' with 4,0L straight six makes most of it's power down low on the tach.I use an HDEO used for diesel applications with SM gas ratings in both gasser with great UOA's results.
Diesel engines also cruise/live most of their lives at low rpm. A good friend that drives on of those big semi-tractor, double clutching e flat trailer trucks says running the open road was usually around 1500-1650 rpm. As explained to me by a tribologist, a crankshaft journal pulls the oil supplied by the pump into the bearing to form the protective wedge. The thinner the oil and the lower the rpm, the more difficult to pull into the bearing. At lower rpm the 40 grade oil is easier to pull into the bearing. I know this is probably a poor explanation, but hopefully you get the gist.
This is why I use 15W-50 synthetic in my gasoline engines that rarely, if ever, go over 2000 rpm.
My gas Jeep engines' with 4,0L straight six makes most of it's power down low on the tach.I use an HDEO used for diesel applications with SM gas ratings in both gasser with great UOA's results.
Quote:
My gas Jeep engines' with 4,0L straight six makes most of it's power down low on the tach.I use an HDEO used for diesel applications with SM gas ratings in both gasser with great UOA's results.
I see that many of the XW-40 diesel oils are also SM rated. I suspect many now use them in hard working gas engines. I also know some folk that use them in motorcycles.
I have a friend that has his own excavating business. He uses the same 5W-40 diesel oil in his bulldozer, end loader, ditch machine, heavy diesel trucks and light(gas) pickup trucks, bush hogs, and heavy mowers. I happen to know that he also uses it in his personal gas pickup and his wife's gas car
My gas Jeep engines' with 4,0L straight six makes most of it's power down low on the tach.I use an HDEO used for diesel applications with SM gas ratings in both gasser with great UOA's results.
I see that many of the XW-40 diesel oils are also SM rated. I suspect many now use them in hard working gas engines. I also know some folk that use them in motorcycles.
I have a friend that has his own excavating business. He uses the same 5W-40 diesel oil in his bulldozer, end loader, ditch machine, heavy diesel trucks and light(gas) pickup trucks, bush hogs, and heavy mowers. I happen to know that he also uses it in his personal gas pickup and his wife's gas car
Originally Posted By: FrankN4
Diesel engines also cruise/live most of their lives at low rpm. A good friend that drives on of those big semi-tractor, double clutching e flat trailer trucks says running the open road was usually around 1500-1650 rpm.
Even that RPM on most recent (last few years) is a bit on the high side for what they normally operate. CAT puts their sweet spot in about the 1300 range for their ACERT engines and Cummins likes about 1350-1425 on the ISX. I typically operate my Cummins ISX at about 1350-1400. Gear ratios on rears have adjusted accordingly. Whereas typical ratios of 3.7 or 3.9 were quite common a few years ago, now typical ratios are 3.25 - 3.55. I have 3.42 with an Eaton 13 with a final ratio of .76 which at 1400 puts me on 65 mph with 22.5 LP rubber. Will pull quite well down to 1200, even with gross weights of nearly 80K lb. Try that with a smaller diesel or (choke), a gasser. Of course running higher speed will put my engine at the 1500 (70 mph) or 1600 (75 mph) range, but since I go thru over 25000 gallons of diesel a year and tires cost me $350 to $400 each, I prefer to keep the speed down to 65 or less. Just a matter of economics.
Oil is really being put upon to perform well under conditions like that. Was using Amsoil AME 15w40 CI-4+ in it. Now on Schaeffer's 9000 5w40 CJ-4. Putting together some UOA comparisons now.
Diesel engines also cruise/live most of their lives at low rpm. A good friend that drives on of those big semi-tractor, double clutching e flat trailer trucks says running the open road was usually around 1500-1650 rpm.
Even that RPM on most recent (last few years) is a bit on the high side for what they normally operate. CAT puts their sweet spot in about the 1300 range for their ACERT engines and Cummins likes about 1350-1425 on the ISX. I typically operate my Cummins ISX at about 1350-1400. Gear ratios on rears have adjusted accordingly. Whereas typical ratios of 3.7 or 3.9 were quite common a few years ago, now typical ratios are 3.25 - 3.55. I have 3.42 with an Eaton 13 with a final ratio of .76 which at 1400 puts me on 65 mph with 22.5 LP rubber. Will pull quite well down to 1200, even with gross weights of nearly 80K lb. Try that with a smaller diesel or (choke), a gasser. Of course running higher speed will put my engine at the 1500 (70 mph) or 1600 (75 mph) range, but since I go thru over 25000 gallons of diesel a year and tires cost me $350 to $400 each, I prefer to keep the speed down to 65 or less. Just a matter of economics.
Oil is really being put upon to perform well under conditions like that. Was using Amsoil AME 15w40 CI-4+ in it. Now on Schaeffer's 9000 5w40 CJ-4. Putting together some UOA comparisons now.
All of our fleet of buses are filled with Petro-Can 15w40 bulk. IIRC they did syn for a while but moved back to dyno for some unknown reason. Transmission fluid is synthetic still, however.
dnewton3
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I don't think you can argue with the success of an xW-40 oil in diesels. Overall, it's a proven grade. If I were in areas where extreme cold starts were not an issue (anything above say zero degF), I'd use 15w40 exclusively.
However, I would say that there are times when 10w30 HDEO does quite well, too.
Myself and Arkapigdiesel both run Rotella 10w30 in our Dmax trucks. I can't speak for him with absolution, but I recall that he was seeking a bit better fuel economy with the lighter grade. Personally, I run it because I put on very few miles per year (less than 6k miles/year = one OCI/year), so I am concerned with cold starts in IN (was down to -11 degF last month here) just as much as hot summer days when pulling my travel trailer. The risk with 10w30 is a bit less "protection", but so far, the UOAs have shown this to be a false concern.
The lighter grade might also burn off (evaporate) a bit quicker, but that's hard to quantify. OTOH, what burns off also allows for more top-off's, which just replenishes the add-pack that much sooner. I used 15w40 Tection Extra a few years back on a summer trip pulling the trailer. I used just slightly less than 1 qt per 100 gallons of fuel consumed. That is right in line with GM's accepted rate of oil consumption. When NOT pulling the trailer, I burn no oil whatsoever. Now that I'm using the 10w30 Rotella, my oil consumption is still nil when running light, and just a hair more when heavily loaded.
My neighbor also runs 10w30 Rotella in his 6.0L PSD F-350. He gets good UOA results as well. With the HEUI system, the lighter grade helps reduce the "romp" (engine surging associated with cold oil starts in HEUI) in winter. Further, he rarely if ever tows anything (maybe 7k pounds a few times a year moving his Kubota from place to place in short trips). For him, heavy loading doesn't present much of an issue.
Some other engine families (ISB, TDI, etc) may not fare as well with thinner fluids, but only experimentation would show the truth. For many, they are not willing to take the risk. There's nothing wrong with that; it's their vehicle, and their decision.
If I were to advise a noob, I'd go with this:
1) using diesel anywhere that temps never get below zero = 15w40
2) using diesel with high mileage accumlations (multiple OCIs per year) = 10w30 in winter and 15w40 in summer.
3) using diesel with low annual mileage (one OCI with no EXTREME towing) = 10w30
4) seeking better fuel economy = 10w30
5) extreme heavy towing year round, with few start cycles, regardless of temps = 15w40
6) do extreme towing, have frequent start cycles, extreme cold/heat, want longer OCIs = 5w-40 "synthetic" in any major brand (you can consider base stock, but group III vs group IV does not show significant points worth arguing about for most applications)
As I said, you cannot argue with the success of UOAs that 15w40 has shown. But what a lot of people haven't discovered yet, is that the quality of protection with 10w30 HDEOs is probably just as good, but there are so few of us out there doing it that the evidence is much more scarce.
You really have to weigh your vehicle use, environment, acceptance of risk, use UOAs, then make an informed decision.
However, I would say that there are times when 10w30 HDEO does quite well, too.
Myself and Arkapigdiesel both run Rotella 10w30 in our Dmax trucks. I can't speak for him with absolution, but I recall that he was seeking a bit better fuel economy with the lighter grade. Personally, I run it because I put on very few miles per year (less than 6k miles/year = one OCI/year), so I am concerned with cold starts in IN (was down to -11 degF last month here) just as much as hot summer days when pulling my travel trailer. The risk with 10w30 is a bit less "protection", but so far, the UOAs have shown this to be a false concern.
The lighter grade might also burn off (evaporate) a bit quicker, but that's hard to quantify. OTOH, what burns off also allows for more top-off's, which just replenishes the add-pack that much sooner. I used 15w40 Tection Extra a few years back on a summer trip pulling the trailer. I used just slightly less than 1 qt per 100 gallons of fuel consumed. That is right in line with GM's accepted rate of oil consumption. When NOT pulling the trailer, I burn no oil whatsoever. Now that I'm using the 10w30 Rotella, my oil consumption is still nil when running light, and just a hair more when heavily loaded.
My neighbor also runs 10w30 Rotella in his 6.0L PSD F-350. He gets good UOA results as well. With the HEUI system, the lighter grade helps reduce the "romp" (engine surging associated with cold oil starts in HEUI) in winter. Further, he rarely if ever tows anything (maybe 7k pounds a few times a year moving his Kubota from place to place in short trips). For him, heavy loading doesn't present much of an issue.
Some other engine families (ISB, TDI, etc) may not fare as well with thinner fluids, but only experimentation would show the truth. For many, they are not willing to take the risk. There's nothing wrong with that; it's their vehicle, and their decision.
If I were to advise a noob, I'd go with this:
1) using diesel anywhere that temps never get below zero = 15w40
2) using diesel with high mileage accumlations (multiple OCIs per year) = 10w30 in winter and 15w40 in summer.
3) using diesel with low annual mileage (one OCI with no EXTREME towing) = 10w30
4) seeking better fuel economy = 10w30
5) extreme heavy towing year round, with few start cycles, regardless of temps = 15w40
6) do extreme towing, have frequent start cycles, extreme cold/heat, want longer OCIs = 5w-40 "synthetic" in any major brand (you can consider base stock, but group III vs group IV does not show significant points worth arguing about for most applications)
As I said, you cannot argue with the success of UOAs that 15w40 has shown. But what a lot of people haven't discovered yet, is that the quality of protection with 10w30 HDEOs is probably just as good, but there are so few of us out there doing it that the evidence is much more scarce.
You really have to weigh your vehicle use, environment, acceptance of risk, use UOAs, then make an informed decision.
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Hi,
Ponch - Firstly the major NA diesel engine manufacturers have very strict guidelines for usable viscosities - and SAE40 (15W-40 mineral,semi-synthetics and 5W-40 synthetics) have been around for some decades now
It has to do with Fleet age profiles and use. Many Fleets have both new and old technology equipment in use and lubricant standarisation is a critical point. In some applications engine lubricants are also used in hydraulic and transmissions too
One critcal factor is the HTHS viscosity minimum of 3.7cP used by many Manufacturers. This can be satisfied by some OW-30 HDEOs when used in very cold conditions (-40C/-40F) and CAT say to use the highest viscosity possible for the cold start ambient
CAT for instance also endorse SAE40 lubricants (0W-40, 5W-40, 10W-40 and 15W40) for use in up to +50C (122F) ambients. No SAE50 lubricanst are endorsed!SAE30 lubricants are "branched off" at +30C (86F)
Once below -30C (-22F) synthetic lubricants are advisable. CAT recommend using an oil heater and a thicker viscosity rather than simply using a lower viscosity lubricant
Some Euro diesel engine families are now using SAE30 (multigrade) lubricants - some have for nearly a decade. This trend will continue. Euro heavy diesel engine oil guidelines have been very strict since the 1970s! The Approval's Lists show this!
Much depends on oil capacity, oil cooling and design parameters within an engine family - and the intended application. Much depends on the vehicle(s) involved too. Remember that "common rail" heavy diesels are now up to 25 years old!
Ponch - Firstly the major NA diesel engine manufacturers have very strict guidelines for usable viscosities - and SAE40 (15W-40 mineral,semi-synthetics and 5W-40 synthetics) have been around for some decades now
It has to do with Fleet age profiles and use. Many Fleets have both new and old technology equipment in use and lubricant standarisation is a critical point. In some applications engine lubricants are also used in hydraulic and transmissions too
One critcal factor is the HTHS viscosity minimum of 3.7cP used by many Manufacturers. This can be satisfied by some OW-30 HDEOs when used in very cold conditions (-40C/-40F) and CAT say to use the highest viscosity possible for the cold start ambient
CAT for instance also endorse SAE40 lubricants (0W-40, 5W-40, 10W-40 and 15W40) for use in up to +50C (122F) ambients. No SAE50 lubricanst are endorsed!SAE30 lubricants are "branched off" at +30C (86F)
Once below -30C (-22F) synthetic lubricants are advisable. CAT recommend using an oil heater and a thicker viscosity rather than simply using a lower viscosity lubricant
Some Euro diesel engine families are now using SAE30 (multigrade) lubricants - some have for nearly a decade. This trend will continue. Euro heavy diesel engine oil guidelines have been very strict since the 1970s! The Approval's Lists show this!
Much depends on oil capacity, oil cooling and design parameters within an engine family - and the intended application. Much depends on the vehicle(s) involved too. Remember that "common rail" heavy diesels are now up to 25 years old!
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40wt oils are used in most diesels because the customers wouldn't trust a 30 wt.
The lubrication of the bearing is dependent on the bearing size, bearing peripheral speed (inches or mm per minute, not rpm) and load on the parts as well as the oil supply. The next engine redesign could have slightly larger bearings to handle 30wt oils if anybody would buy them. Very large diesel engines use 30wt oil in the crankcase. Medium sized engines (locomotive size) and smaller usually use 40wt.
10W-30 or 5w30 HDEO would result in a real fuel savings...just a couple of percent but significant nationwide.
The lubrication of the bearing is dependent on the bearing size, bearing peripheral speed (inches or mm per minute, not rpm) and load on the parts as well as the oil supply. The next engine redesign could have slightly larger bearings to handle 30wt oils if anybody would buy them. Very large diesel engines use 30wt oil in the crankcase. Medium sized engines (locomotive size) and smaller usually use 40wt.
10W-30 or 5w30 HDEO would result in a real fuel savings...just a couple of percent but significant nationwide.
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