6.9 IDI Burning Oil Excessively

david85

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I'm currently driving it to and from work, 45 miles both ways, 5 days a week. It's a mix of highway, city, and backroads driving, but mostly highway at 60 mph, so maybe 3,000-ish rpm (no tachometer).

I wasn't overly concerned about the oil consumption, but I thought if there was an easy fix, it'd be nice not to have to top it off so often and save some money on oil. Sounds like it's not out of the ordinary, so I'll probably just keep driving it as is for a while.

Mine used to do the same on the highway (I was usually at 2400-2600). The stem seals could probably be done on a weekend, although I'd pick a long weekend just in case. Although I prefer not to spin up to 3000 all day, these engines can take it.
 

Kevin 007

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I think it's funny that an extra quart between oil changes is considered not a lot, but then they aren't called oil burners for nothing! And of course, here I am adding sometimes almost two quarts in a week.
Ya no doubt. Although of course it's not desirable to burn that much oil, it's not uncommon for the age of these engines and doesn't necessarily mean it's days are numbered. I tend to not worry about it too much if it runs good, just keep it topped up and one day you'll get time to look into it a little further
 

PossumF250

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Mine used to do the same on the highway (I was usually at 2400-2600). The stem seals could probably be done on a weekend, although I'd pick a long weekend just in case. Although I prefer not to spin up to 3000 all day, these engines can take it.

At roughly 60mph/3000 rpm, it's really loud and considerably less efficient, but I try to keep it there just to avoid getting run over on the interstate. 3.55's and overdrive are definitely in my plans for the future! Oh well, it's fine for now, and maybe I can replace the stem seals once the weather warms up and I get my backup car on the road again.
 

PossumF250

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Ya no doubt. Although of course it's not desirable to burn that much oil, it's not uncommon for the age of these engines and doesn't necessarily mean it's days are numbered. I tend to not worry about it too much if it runs good, just keep it topped up and one day you'll get time to look into it a little further

That's good enough for me! I figure as long as I keep up with the glow plugs, starter, and batteries, etc. that engine will probably just about keep going forever.
 

1mouse3

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At roughly 60mph/3000 rpm, it's really loud and considerably less efficient, but I try to keep it there just to avoid getting run over on the interstate. 3.55's and overdrive are definitely in my plans for the future!

Yea, with 4:10 and no overdrive the interstate is no longer a safe place to be. I try to stay at 55mph and 2500rpm max for now till I switch the rear to 3.55, that is what the front axle is. I can stay at that if I take rural routes if not within a city/town.
 

IDIBRONCO

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At roughly 60mph/3000 rpm, it's really loud and considerably less efficient, but I try to keep it there just to avoid getting run over on the interstate. 3.55's and overdrive are definitely in my plans for the future!
The 3.55 gears will make a big difference even without the overdrive transmission.
 

Kurt_M

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I have found on my 6.9, as it gets aged more it becomes more sensitive to a new air cleaner element. My oil consumption begins to go up long before the air cleaner seems dirty.
 
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rempfer

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When you change the oil, remark the dipstick for 10 quarts and see if the consumption continues. Wouldnt be surprised if it does, I have had many 6.9s that would use a quart per tank. A local here has an 85 that he bought with 50k on it in 1990, has always burned a quart at 500 miles........I have NEVER had a 6.9 that burned less than that......with original ring gap specs and valve seals.
My 7.3 with unknown history burns a quart per tank (fill-up). As well as it runs, I never thought to make that an issue. I have not looked to see whether the intake manifold is wet.
 
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Isaac Ristow

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What gears and transmission do you have now? These motors will run against the governor all day long safely but they will burn oil doing it you just need to keep the oil full. My plow truck is a 86 c6 it had a replacement 7.3 put in I forgot the gear ratio but it likes the high revvs and it does burn oil the engine is very tight and no blow by too. The 6.9 is especially worse because of the valve guide and seal design they are made to burn the oil that passes the valve seals to lubricate the valve guides and valve stems with the added speed these days (they were not meant to go over 55 in their day) the oil starts really flying around in the valve cover and more gets passed the valve seals and with the added rpm the 6.9 had larger ring gaps thats going to push more crank case pressure with more rpm and oil will make its way though the cdr. Now you could replace the valve seals if your concerned or you could just keep running it and keeping oil in it. I run Mobil delvac 15w40 with a quart of Lucas try that. My other idi is a 84 with a turbo 7.3 zf5 and 4.10 gears but even with the 4.10 gears the zf5 is taking control and it runs less rpm than the plow truck with the c6 and it does not burn any oil. If it were my truck I would try delvac and lucas and see if that helps and keep running it. A overdrive will really drop oil consumption more than you'd think
 

BrianX128

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I'm using Delo 15w40. I went with Delo because I'd heard these trucks love to burn Rotella like you're talking about.

Also, I don't know what was in the truck when I bought it, but I've only used Delo since buying it, so I have nothing to compare to in terms of how much oil it burns when using different brands. Could it be worth switching to see if something else works better?

My 7.3 has 140k on it now, when I got it at 100k it was burning a quart of delo every 1000 miles. That's what the previous owner was using. I switched to rotella just for fun and it only burns a quart ever 2000 maybe slightly less 1800 we'll say but for sure better. Doesn't make sense. My 6.9 will burn a quart of rotella every 1000 but doesn't burn almost any delo for normal 3k oil changes.
 

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