Brad5502

My 200K mile oil analysis had a high aluminum readout (18 vs normal 3-5), see attachment.

My last three MPG (hand calculated) were between 16.5-16.7. For the last 200K miles, I've been averaging 17.5-18 (also hand calculated).

Any thought? Is this sudden difference in MPG and Aluminum in the oil, happening at the same time, a coincidence or something that points to a specific problem?

Had injectors replaced at 165K miles.

I'm fixing to go on a trip from San Diego to WA State, then back in a few weeks, towing my 13.5K fifth wheel. Anything I should check out before I go?

Steve-l

The fuel mileage difference is normal, especially considering the large difference in fuel consumption with driving speeds these trucks exhibit. Your concern should be the aluminum in the oil. There are few components in the engine exposed to circulating lube oil. I can think of pistons and the high pressure fuel pump as major candidates, but they are not my first guess. Please also note that the lead has also doubled and the copper has increased. These three elements make up the constituent layers of engine bearing shells. I also noticed that your oil viscosity numbers are higher. it appears by this report that you are running the wrong oil for the motor. Do you have other indicators like lower than normal oil pressure or unusual engine noise?

The purpose of using spectrum analysis of your oil is to preclude expensive maintenance costs by early detection of potential faults. This report warrants dropping the oil pan and checking the bearings.

Brad5502

I was thinking maybe turbo bearings (but no contact with oil, right) or pistons, but the engine bearing shells also make sense. Haven't done any heavy towing or anything to damage the pistons on this oil run.

I've been running Rotella 15W-40 for the life of the motor. Viscosity has been pretty consistent over the years. Oil pressure and temps were totally normal and no unusual engine noises.

If I drop the pan, what am I looking for on the bearing shells?
-Uniformity of thickness? Any spec. measurements that can be checked?
-Any common signs of unusual wear to look for?

Brad5502

Also, would damaged bearing shells cause additional friction that might account for the drop in MPG. For 10 years, I've gotten between 17l5 and 18.5, like clockwork on every fill-up, unless towing.

Last three fill-ups before the oil analysis were 16.5-16.7.

Does additional friction make sense? If so, wouldn't I be seeing higher oil temps?

Just thinking out loud. Thoughts anyone?

Steve-l

Checking bearings is easy and visual for the most part. The only possible complexity may be dropping the oil pan because of chassis clearance..........I haven't looked. Since you haven't done this before, it is best to do this with an experienced person along side you.

Brad5502

Thanks Steve,

I've got a friend with a lift at his garage. We'll take a look at the bearings.

Hope you're enjoying your time in GE. Wife and I loved it. Zuchspitze skiing, climbing Gross Glockner and the Wildspitze. Garmish and Ettal. Make the best of it while you're there.

400HP

Brad,

Little late commenting here but I do have some thoughts:

If your mileage has changed you know it because you know your truck. Not sure if it is related though.

Generally if your oil sample comes back with any anomalies you should resample to confirm. Labs do make mistakes. Make sure your sampling is consistent also. Time may not be on your side here so not sure if that is an option but there is a chance your chasing a non existent problem(slim chance but you never know). Also resample much more often if you choose to keep running it to keep on top before something does fail.

Although your lead has doubled, going from 2 to 4 is not a big concern. The labs error factor is probably that much. 4 ppm lead with oil having 11000 miles is not bad at all. Call your lab and they will tell you the same. I've seen oil samples with lead at 80 ppm (very high) to give some perspective. That engine went on to live a normal life with an oil brand change.

Call your lab and talk to the lab manager or a lab tech. They are a great resource. They can tell you at what levels to be concerned at and provide a perspective from someone who does oil analysis everyday.

Your viscosity is right on where it should be for 15w40 oil (and is consistent as you said) Last I checked that was the recommended oil for your engine and Rotella is good proven oil.

Personally I don't think your bearings are the problem as it usually shows high lead. Most sources of aluminum are pistons. You fuel content is also normal so it doesn't appear like you have an injector problem (stuck open at least).

I wish I could be more help. If you find the source be sure to post up any findings.

Brad5502

Took it to my mechanic. We talked about the analysis. He said "Drive it" and "Get another sample in 5K miles".

So, pulled the trailer to WA state and back from San Diego.

Figured the fuel mileage out on the first big grade (I didn't reset the Smarty to level 1 after my Smog check). From then on, my fuel mileage was back to normal.

Will send in the oil analysis in about 1K miles.

Bottom line, truck ran fine but my clutch is starting to slip, so I'm looking at replacing that soon.