Oil Coloration (8v71s)

[DAlter]

I have an interesting situation with the color of the oil in my 8V71s (53MY). After changing the oil at the begining of last season and running for a few hours I noticed (upon checking the dipsticks) that the oil in the port engine turned dark, which is expected in diesels. However, the oil in the starboard engine remained "clean" looking the entire season. I mentioned this to a fellow baoter who pointed out that I may not have completely drained all the old oil from the port engine. Well, after changing the oil this season and running for 60 hours, the same thing is happening. The performance of both engines is the same (oil pressure, temperatures, smoke, etc.).

I doubt there is anything wrong as the engines perform perfectly. Has anyone experienced this?

Doug

[Brian Degulis]

I've seen that before and as long as the correct oil is being used the only explaination I can think of is that one engine is tighter than the other. I've seen some engines with exceptionaly clean oil only to find out that the owner is using automotive type oil. As long as your using the right oil I wouldn't worry about it.

Brian

[DAlter]

Same oil in both (Delo 100 40Wt).

[Genesis]

A very, very few diesels don't turn oil black. Very few.

Its all about how much carbon gets into the oil. Most diesels gets plenty in there, but a few are tight enough not to.

Don't complain if you got one of the "tight" ones!

[DAlter]

No complaints here...it was just a curiosity thing. What do you guys mean by "tighter"?... in mechanical terms that is.

[Thomas W Peavy]

Pretty much the same concept. The rings and pistons fit the cylinder with closer tolerence. The looser the fit the more the piston moves around in the cylinder and more the rings move around in their grooves. Its not like the piston wobbles up and down as it makes a cycle but it does move around ever so slightly so the less the better.

[MikeP]

Acceptable factory clearance tolerances (what you see in the service manual) are designed for mass production. Nobody is checking all those clearances in a new engine. So, as part of normal production, sometimes you get an engine (this is totally by luck, nothing else) where all the clearances are on the narrow end. Those engines produce less blowby, less oil consumption and more power. Most engines fall in the middle somewhere, and some are also, by luck, produced at the wide end of the clearance limits and you have an engine that is the opposite - uses oil, produces less power, etc.

We used to get new identical (gas) engines for performance rebuilds (blueprinting, etc) and found as much as 30 HP difference between identical production engines, all based on the variation of the factory-assembled clearances and differences in the block castings/cyl wall thickness in the thrust-direction. All based totally on luck!

[Salty Dame]

I have the exact same conditions on my 8V53's. Engines that I overhauled on alternate years. I attributed the difference to my not being able to break in the port engine (dark oil) as well as the starboard. Sometime's I have wondered if I had problems but otherwise they are operating identically so maybe now I will relax.

[ThirdHatt]

We used to get new identical (gas) engines for performance rebuilds (blueprinting, etc) and found as much as 30 HP difference between identical production engines, all based on the variation of the factory-assembled clearances and differences in the block castings/cyl wall thickness in the thrust-direction. All based totally on luck!

Mike, this is still true of some current high performance engines as well. I have an account with Renntech, the premier Mercedes tuner and they have confirmed that there is as much as 30hp and 25lbs of torque difference in the AMG hand-built V12 Twin Turbo engines from the factory. Bone stock the official rating is 604hp and 738tq and after tuning they are close to 700hp and 845tq. They actually produce just over 1,000lbs of torque but they have to be restricted to under 900 to allow the tranny to live a long life.

These are actual real numbers well proven over and over on a dyno and they are dead reliable with full factory warranty. They even get about 23mpg at 75mph as well! There is one engine builder that assembles each AMG engine from start to finish and signs the top of the engine. Some builders are better than others and this is where the hp and torque difference comes from. Within Mercedes performance circles it is a highly coveted list of which engine builders have a reputation for the "tighter" motors than others.

I, for one, am just tickled that technology has come far enough to allow us to mass produce engines that make these levels of power and yet are fuel efficient, reliable and still covered under factory warranty. Not long ago it was usually ticking time bomb engines that made this kind of power and if you asked for warranty they laughed you out the shop!

[MikeP]

Interesting - of course they are doing much better now since 30HP variation on a 600+ HP motor is far better than 30HP on a 300+HP motor! We actually found much greater differences than 30HP among engines on some occasions but the 30HP variation was common on new "crate engines." Off the street cars with the same engines and no mods that had been running for a while sometimes showed as much as 60-70HP difference.

Virtually all of the HP difference in every case had to do with cylinder wall/piston ring sealing since on virtually any production engine, the cylinder bores are not round when the engine is warmed up which means the rings can't seal properly.