Hi all,
I have heard this statement enough to ask around. A number of bus folks (charter and private) have told me to consider running my 8v71 a gallon low on oil, their logic being that the first gallon leaks/burns way faster than the remaning gallons of oil. I haven't had the bus out enough this year to check but I do remember that my bus seems to go through a gallon of oil every 300 miles but the weird thing is, it only goes through a gallon to go 800-900 miles as well. All my instincts say better safe than sorry so I fill my bus pretty religiously. I just figured I would ask and see what you folks thought.
Thanks in advance,
Rick
I'm no expert , however I have run several different types of diesel engines. What I found was different engines like different levels. I wouldn't say run it a gallon low but try to figure out at what level does it use less oil. I don't see a problem running a gallon low but I wouldn't run it any lower than that. I believe several engines like to be run about half a gallon down from the full mark, which won't hurt them. That's the short version.
Have Fun
Grant
to clarify, to run it a gallon short are you referring to a gallon below the full line, or a gallon below the low line? thanks!
My 8v71 likes to run a gallon low. When I first bought our Eagle I always topped it off, then after several times it would read low I just let it be. There seems to be a sweet spot on mine or whatever you want to call it. I don't know why but I keep checking and it stays at that level.
If that is the wrong way please clarify so I know what's right!
One gallon below the full mark! ;)
FWIW,
Paul
A couple John Deere engineers were on an RFD call in show a few months ago. someone called in about excessive oil consumption on their tractor. Here is what the emgineers told them to do. Fill the tractor to the full mark and use it all day. The next morning check the oil, as long as it is above the add mark, don't add any oil, just use the tractor all day. Most likely, the next morning the oil level will be where it was the morning before. They said that each motor has an oil level "sweet spot" and they are not all the same. The add mark means add oil, the full mark means do not fill above this mark. The space between ADD and FULL is the SAFE zone'
That said, we have found that our engine uses less oil when maintained about 1/2 way between ADD & FULL. Jack
Can I add My thoughts to this topic? My 8v71 seemed to like to run a gallon low meaning it always lost a gallon rather quick! When I changed the oil last time I filled the oil filter and filled the engine with a total of 7 gallons which the manual and a note from a PO said to use! Low and behold I found that the mark on the dipstick was not accurate and My guess is that it is the wrong stick for this engine. Try it ,it might open your eyes and then it might not help at all. Hope this gives You another angle. John
By the way I did put a new mark on My stick and I now burn about a quart every 7 to 8 hundred miles
I have heard that having the wrong dipstick is a common problem on these old beasts.
Iminaccess,
I was referring to a gallon below the full mark.
The answers here were eye opening to say the least. Thanks All...
Rick
My 82 mci 9 does good at about 3 quarts from the full mark. It is an 8v71 . Marc
I run my 671 2-3 qts low all the time. It seems to throw out the first half gallon quickly when filled to the full mark.
When it gets around a gallon or slightly more low (Below the Full mark) the oil pressure drops below 40psi. I usually add a couple of quarts then but sometimes I let it drop to around 30psi before adding 3-4 qts.
It runs at 50+psi when 2-3 qts below Full.
Quote from: gus on February 12, 2009, 04:12:29 PM
When it gets around a gallon or slightly more low (Below the Full mark) the oil pressure drops below 40psi. I usually add a couple of quarts then but sometimes I let it drop to around 30psi before adding 3-4 qts.
It runs at 50+psi when 2-3 qts below Full.
While I feel that many buses have inaccurate dipsticks and agree that they may vary somewhat in proper fill level, I would never allow it to get low enough that oil pressure drops even just a little. I would attribute a drop in oil pressure under those circumstances to be from the oil temperature rising as a result of less volume in the sump. The oil plays a significant role in cooling key areas of the engine. In a more extreme low oil situation, it could even be the pump starting to draw air, an even worse prospect.
The manual states:
QuoteDuring operation, normal pressure is 40-50psi (275-345 kPa) at moderate engine speed. Pressure should range from 50-70 psi (345-480 kPa) at engine governed speed. Minimum safe operating pressure should be 20 psi (140 kPa) at moderate engine speed.
From what I've read the proper level for the oil with the engine off and cool is 1" below the top of the oil pan. If an engine doesn't seem happy with the oil level at the full mark when cool, as a first step I would check the accuracy of the dipstick. To do that, measure down from the top of the dipstick tube to the top of the oil pan following the path of the dipstick tube. Then measure the dipstick from the part of the cap that corresponds to the top of the tube down to the measurement plus 1". If that differs from the existing full mark, scribe a new one into it.
Hightech redneck has a good point, HOW DOES ONE KNOW YOU HAVE THE RIGHT DIP STICK. I ask this question too, because
mine seems Little short for the size of the engine. It's a 8v-92n and it only holds 20qts or 5gal.
Steve 5B........
My 8-71 used to use a gallon every 300-500 miles untill I learned how to check it. I check it cold before the first start up of the day only when it is sitting level. It seems like there is oil up inside the engine that takes several hours to drain back down to the pan. It used to be that I would check it when filling up. The oil would show low and I would add oil to the full mark. Then it would blow out this extra oil over the next few hundred miles and it would be low the next time I filled up. The bottom line is that it was never low to begin with. It just had oil in the motor that had not had time to drain back to the pan before I checked it. Now I generally do not ever have to add oil between changes. With that said I change it annually because I do not put enough miles on it most years. Only 2-3 thousand but that is pretty good without having to add oil.
My .02
I have a truck drivin buddy that claims back in the day when he drove a truck with the old 318 DD that it used a gallon of oil a day whether he drove it or not!! ;D ;D That and he slammed his hand in the door everytime he got in it just to get his frame of mind correct for driving it. For some reason I was under the assumption that my 8v 71 held 11 gallons of oil. I hate getting senile and forgetting stuff!!! Did I tell you about an old truck drivin buddy of mine that used to drive a truck with the old 318 DD in it? It used a gallon of oil whether he was driving it or it was sitting still!! :D :D Later
Mike Meloche (great expertise/DD rep/really neat guy) use to come to the various BC rallies. The question came up several times, and his answer was the same as HTR said. Full should be 1 inch below the bottom rail of the engine (top of the pan).
I don't have my Series 60 manual with me, but I am 95% + sure that it is the same value. I remember calibrating my dipstick and it was off a little bit.
Jim
Yes, the drop in pressure is due to the decrease in sump volume of oil. That is when I know for sure to add more!!
If an oil pump draws air the needle will jump around. Had that happen in an airplane once and had to keep the nose level, pressure dropped every time I lowered the nose.
30-40 psi oil pressure is never going to result in any problems at moderate speeds (60-65mph) and probably not even at slightly higher speeds in a non-turbo DD.
The oil may get hotter but my engine runs so cool I don't worry about that.
The best way to check a dip stick is when you refill it after you change the oil and know exactly how much you have added. Check it as you fill it.
Somewhat related, but I worked summers at a fairgrounds that used a very old Farmall tractor to cut grass. The oil pressure gauge was reading zero one summer and we assumed the gauge was bad. It turned out the operator of the tractor hadn't checked the oil ever that summer and the oil level was WAY down! Once the oil was filled the gauge started reading the oil pressure properly
The engine didn't seem to be hurt by zero oil pressure and it was used 40 hours a week for another 10 or 15 years before it was replaced by a new John Deere.
The moral is if you see zero pressure on a oil gauge, don't assume it is broken!
On the GM coaches that have the torus fan drive you will find that oil level is very critical at times. On my 4106 with V730 here's what I have occasionally noticed when driving uphill, and especially in hot weather:
Over time the oil pressure would gradually but slowly degrade to about 35 or 40 psi, and the coolant temp would rise to 200 or so at the same time. Each time this happened the oil showed a gallon or more low. I then added enough oil to bring it up to the full mark and the oil pressure returned to 45 or more and stayed there, and the temperature went back to 175 to 185 and stayed there.
Some folks argued that it's natural for oil pressure to fall in an overheat situation, but I believe it's equally likely for a low-oil situation to cause overheating. However in my case I have concluded that when conditions dictate, the torus drive gobbles up and holds a gallon of oil or so, robbing it from the engine lubrication and cooling functions. So, if the oil level is below full, overheating and pressure drop may occur.
I once thought about solving this little problem by installing a separate oil tank and isolating the torus from the engine, using the old manual transmission oil pump to supply the torus. But more recently I have changed my mind. The engine now has about 19000 miles on it after a major out of frame rebuild and the problem did not recur on the last two trips, totaling about 3000 miles during which the oil level remained at the full mark.
Thus I think the problem only showed up during the break-in period. But it should also be noted that the same problem would llikely occur equally or more so in a tired engine.
tg
When I had my 4104 it would loose a gallon (from the full mark) within a few hours while driving. A gallon low seemed to be the sweet spot for the oil level. The 8v71 in my MCI will only loose maybe 1 qt every 3000 mi from the full mark. I think the biggest factor is the condition of your engine and how well it's sealed.
The oil dipstick markings are determined by stand testing of one of the first production engines. They put the engine on a test stand and run it at various throttle settings, while they keep an eye on the oil level. First they find "Test Low," the minimum level which will keep the oil pump inlet fully immersed at all RPM settings, then they find "Test High," the level which keeps the top of the oil below the bottom of the pistons at all RPM settings. Remember, there is a hurricane in the oil pan, as the pistons move up and down (every CC of displacement in the combustion chamber is also a CC of displacement in the engine bottom end), return oil flows back into the pan, and the crankshaft splatters oil up into the cylinders.
Once they have Test Low and Test High, they move the ADD mark up and the FULL mark down, to make up for ullage (change in level due to sloshing, tilting, etc).
This means that the marks on the dipstick are not precise levels, they are based on a combination of testing and SWAG (Scientific Wild-@$# Guess). Each individual engine has its own sweet spot for oil level, and when you find yours (the way the Johnny Deere guys said to do it), take a file and put a small nick in the side of the dipstick right at that level. As long as your level is between there and ADD, you're okay. As long as you're at or under FULL, you're safe from slapped pistons.
The marks on my dipstick (no not that dipstick) are about 2 gallons apart. If the oil gets down to the low mark it takes almost 2 gallons to get it up to the full mark.
When full it will drop down to about the middle of the marks really quick, then it wil take longer to drop down to the low mark. I keep the level in the middle.
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