Oil Consumption on DD 8v71 N

[Barney]

Need to ask a question about oil consumption on 8v71n's. On a trip of 1000 miles, my 53 MY w/ 8v71N burns approximately 8 qts of Oil per engine. Rebuilds were done about 15 years ago and total time is about 5000 hours. Engines now have approx. 3000 on the rebuilds. I am starting to see a small amount of blue smoke from my SB engine while running. I have the typical small amount of slobbering from airbox vents, etc. but nothing else alarming.

Is this pretty typical for what everyone else is seeing on their 8v71n engines? I know these engines will continue to run even when they are shot, so what is the rule of thumb for when it's necessary to do so. By the way this level of oil consumption has stayed about the same over the last 5 years and so far has not been increasing.

Thanks for any advice.

[TedZ]

How far do you go each day? Makes a difference on how hard they are running. Say you cruise for 200 miles per day and add prox quart and a half per engine per day. That would be very close to my usage in 8V53's for 200 miles and i think they are perfect two stroke Detroits!

Now if you are going 50 miles per day, that is quite a bit of oil.

Ted

[Barney]

Run at 1100 to 1300 rpm for 100 miles a day.

[mike]

FWIW, has you consumption/burn rate increased over time? Does the usage reach a steady state point where the oil consumption levels off? Some times adding oil to the full mark places the level too high, resulting in accelerated consumption until the oil level reaches an equilibrium point. On our 53MY with the 8v71N's running down a few quarts from full will result in little additional oil burn over a 100 hr interval.

[REBrueckner]

I know oil consumption has been discussed before because I posted data for my 8V71TI's and prior 6V53's....can't find it via search, but it's here somewhere....and I don't remember for sure my consumption figures....

I find that running hard, say 2,000 RPM uses more oil than slower RPM, say 1200 to 1500 RPM....not surprising....How many hours did you run for the 1,000 miles??....let's say you were doing 9 knots; that's about 111 hours...I'd say 2 gal oil per engine is not unusual...that's a gallon per 50 hours...

A bit of smoke could easily be an injector a bit off....

One thing that's nice...the old Detroits usually just slow a bit, nothing major as they age, and can continue to provide reliable service even when everything is not tuned to perfection....

[MikeP]

I haven't "filled" an engine oil sump to the full mark in years. Old muscle cars did the same thing that my DDs do - if you fill them to the full mark, they use oil until the level drops to around the add mark. Then they virtually quit using oil. At oil change I fill my 8v71ti s to just a touch above the add mark. The oil level remains at that point until the next oil change.

This is with runnning at displacement speeds, 9-10 knots. Since they ARE DDs, I would expect them to use some oil between changes if I ran predominately at planing speeds.