Run two strokes a gallon of oil low to curb oil useage. Myth or fact?

[RickB]

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

[busshawg]

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

[ilyafish]

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!

[Dreamscape]

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

[JackConrad]

   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

[junkman42]

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

[HighTechRedneck]

I have heard that having the wrong dipstick is a common problem on these old beasts.

[RickB]

Iminaccess,

I was referring to a gallon below the full mark.

The answers here were eye opening to say the least. Thanks All...

Rick

[Marcus]

My 82 mci 9 does good at about 3 quarts from the full mark. It is an 8v71 . Marc

[gus]

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.

[HighTechRedneck]

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:

During 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.

[steve5B]

   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........

[Charles in SC]

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

[Chopper Scott]

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!! 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!!    Later

[rv_safetyman]

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