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Author Topic: 8V-71N "Normal" Oil Consumption?  (Read 4413 times)
Debo
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« on: October 31, 2014, 12:24:36 PM »

Hi guys,

I'm getting ready to take the bus on its first long trip (1500 miles round-trip.) We're leaving the Outer Banks of NC and heading to Cedar Key, Florida in December. I've done many short trips of 100 miles or so, but I'm curious what would be considered a reasonably normal rate to expect my 8V-71N to burn oil on a long trip like this? Since my little hops have been kind of short, I don't really have a good feel for it yet. It fires up great, has good compression, and the rings still have healthy inspection grooves. No smoke to speak of, and she makes good power. Things appear pretty healthy to me, so I'm wondering how much oil might I expect to burn on the trip? Things I've read lead me to believe that a quart every 500 miles might be reasonable to expect. Does that sound about right to folks? For the record, I'm using Shell Rotella T straight 40 weight CF-2 rated oil.

Thanks in advance.
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1981 MCI MC9
Detroit 8V-71N
Spicer 4-Speed Manual
Outer Banks, NC (Nags Head)
Frank @ TX
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« Reply #1 on: October 31, 2014, 12:44:52 PM »

Hi Debo,
I have a 6V92 and have to add about 2 to 3 quarts between oil changes ( 10,000 - 12,000 miles ).
The engine has no leaks that run to the ground but it does have two wet spots.
If you have any leaks take care of them , the engine will look better and run cooler.
Frank
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luvrbus
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« Reply #2 on: October 31, 2014, 01:46:35 PM »

Oil consumption on a DD is based on the rpm I can give you the average burn rate from the book for a 10 hr day but to be clear this is for a engine running 10 hrs at a continuous 1800 rpm under load so it will vary +or - the book says 1.25 qts  go to 2100 rpm 2 qts per 10 hrs and that is all DD gives you just a average
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Cary and Don
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« Reply #3 on: October 31, 2014, 03:21:03 PM »

The real question should be, How much oil should I take?  We carry four gallons.  If something really horrible happens and a line goes, or some other major problem,  we will have enough oil without having to find the hard to find Delo 100.  We just finished a 1400 mile trip with the Eagle, heavy, and a 8V71.  It used less than three quarts with some really hard climbing over most of the trip. On the flat, it hardly uses any on a trip of that length.

Don and Cary
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Nineforever
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« Reply #4 on: October 31, 2014, 03:40:38 PM »

If space isnt a problem run with a couple cases on hand
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thomasinnv
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« Reply #5 on: October 31, 2014, 03:56:02 PM »

For my tired old girl, "normal" oil consumption is a gallon about every 400 miles.

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« Reply #6 on: October 31, 2014, 03:57:44 PM »

I think I've added maybe 1-2 gal to mine since I got it in Dec. '10 and have gone 30,000 mi, but there are wide variances in these engines so that is only a guide. It was supposedly o/h not long before I got it.

My 4104 671 used a quart or two/500 mi but it had a lot more wear.
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bevans6
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« Reply #7 on: October 31, 2014, 03:59:12 PM »

 one gallon per thousand miles is trending towards high, one gallon per three thousand miles I would be happy with.  Some people get twice that.  It depends on many different parameters, but the 8V-71 is not a conservative engine from an oil consumption point of view.  My engine is at the 2 to 3 thousand miles per gallon stage but it is quite new, only have about 4,000 miles on it at this point.

Take a case of three gallons with you, check the oil level at the same bus level and temperature.  The difference between hot and cold is about a half gallon in terms of simple expansion with temperature.   Also, these engines often use far less oil slightly underfilled.  I try to keep mine just over the fill mark on the dip stick.

Brian
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luvrbus
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« Reply #8 on: October 31, 2014, 04:50:44 PM »

LOL depends on the oil brand also the DD likes clean oil
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TomC
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« Reply #9 on: October 31, 2014, 08:20:30 PM »

I carry three cases of Delo 100 40weight (12gal). Then you have enough for a complete oil change and then some. Good Luck, TomC
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Tony LEE
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« Reply #10 on: October 31, 2014, 08:56:25 PM »

I carry a 4 gallon can - mostly for "just in case"

Fill it up to the top mark and it will use far more oil than if filled to half way between max and min.
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niles500
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« Reply #11 on: October 31, 2014, 09:14:42 PM »

As Tony said, put it at the full mark then monitor it to see if it settles at a certain point on the dipstick and maintain it there and see if the consumption goes down. There is the sweet spot. FWIW
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« Reply #12 on: November 01, 2014, 11:21:17 AM »

We used about a gallon on a 3000 mile trip last year. I keep it just below the full mark on the dipstick, as said already, there is a sweet spot..
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Bruce & Nancy Fagley
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« Reply #13 on: November 01, 2014, 07:18:21 PM »

one gallon per thousand miles is trending towards high, one gallon per three thousand miles I would be happy with.  Some people get twice that.  It depends on many different parameters, but the 8V-71 is not a conservative engine from an oil consumption point of view.  My engine is at the 2 to 3 thousand miles per gallon stage but it is quite new, only have about 4,000 miles on it at this point.

Take a case of three gallons with you, check the oil level at the same bus level and temperature.  The difference between hot and cold is about a half gallon in terms of simple expansion with temperature.   Also, these engines often use far less oil slightly underfilled.  I try to keep mine just over the fill mark on the dip stick.

Brian

A very good point, I learned long ago to never fill any engine to the full mark.

I had an airplane that would throw out the first quart in ten minutes then go on for hours on the next quart. Same with both my DDs and just about every other vehicle I own.
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« Reply #14 on: November 01, 2014, 07:38:36 PM »

"normal" oil consumption? On my old leaky 8v71, if I fill it to the full mark, it will "leak" out 1/2 gallon in no time, If I run it at the low mark, it will go 1000 miles and not leak 2 quarts. YMMMV. Oh yea, Your Milage May Vary. In 1o years, if I keep it at the low level, I have to put in half as much. I do not know if that is "normal" but ,,,   ,,,   ,,, with an old 2 stroke I think it is "normal". I agree, take more with you than you burn or leak, I do not want to have to mix along the way.
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« Reply #15 on: November 02, 2014, 11:04:30 AM »

Why is that so?  The oil pump should be moving the same volume of oil regardless of oil level.  Does adding that last quart of oil cause the crankshaft to splash excess oil onto the cylinder walls?  I am not doubting you-- many people have said the same thing... just curious.
« Last Edit: November 02, 2014, 11:06:33 AM by sparkplug188 » Logged
luvrbus
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« Reply #16 on: November 02, 2014, 12:31:54 PM »

Most of the time when the old 2 strokes blow the oil out there is to much by pass on the compression causing the oil to foam and they suck it out from bad pin seals 

I never run one a gal low it causes the oil temperature to rise if it blows the 1st gal out there is problem somewhere could be simple like the engine ventilation no one ever cleans the vent on the back of the engine on a old 71 series I have had to dig the dirt from those before a air compressor was no use     
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Scott & Heather
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« Reply #17 on: November 02, 2014, 01:45:42 PM »

My bus has a nice little 2 gallon holding barrel mounted to the engine that i can fill (has a sight glass) and then use a valve to add oil as needed. very cool, very handy.
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Scott & Heather
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Debo
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« Reply #18 on: November 02, 2014, 03:01:01 PM »

Thanks so much for the great answers guys. After reading tons of stuff including your comments, I'm thinking I'll be fine with the 3-gallon case I bought for the trip. I haven't seen anything crazy in terms of consumption on my shorter trips, and my engine is in pretty good shape. I'll be on I-95 for a lot of the trip, so it'll probably be much easier to find straight 40-weight along the way than it was to get it here. I doubt I'll need it, but I'll probably pick some up because it's available. Before even reading about it here, I had noticed that my engine likes to run with the oil level slightly above the fill line on the dipstick. Anything above that disappears before too long, but it never gets any lower than that mark. That must be the "sweet spot" you guys are talking about. Scott - I've read about the oil reservoir in my parts book. Pretty cool. I kinda wish mine had that.

Thanks again for the great answers. After a few years on the board, I've found that the way to get people talking is to ask 'em about anything related to oil.  Cheesy
« Last Edit: November 02, 2014, 03:02:35 PM by Debo » Logged

1981 MCI MC9
Detroit 8V-71N
Spicer 4-Speed Manual
Outer Banks, NC (Nags Head)
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