To change (the oil), or not to change...

[Frank P. Martin]

...that is the question?

I have a little over 3k miles on my Duramax now. I checked the oil the other day and, on the dipstick, it looked really dirty, just like the oil on my 7.3 PSD did when I would change it at the required interval-- every 3,000 miles.

The DIC computer says that I still have 44% oil life remaining and my last OnStar Vehicle Diagnostics Report indicated the same percentage life. Based on this OnStar estimates that the oil won't need changed until around 5,600 miles.

But, judging by the visual appearance of the oil on the dipstick, I think it should be changed.

Is there anyone out there (especially those with the LMM engine), that can share what their experience has been regarding when to change the oil? Should I trust the computer or my own analysis?

Personally, I'm leaning toward changing it now because I estimate the truck will most likely have 5,600 miles on it sometime during the dead of winter and I change my own oil (outside because my truck won't fit in my garage).

[Hitchhiker]

Oil in a diesel will get sooted shortly after an oil change and will look black. You can't determine oil condition by observing how it looks. I usually let my DIC get to about 25% and then I change it, by then it usually has gone about 5,000 miles or so.

An option would be to have the oil analyzed and change per their recomendation. One that comes to mind is Blackstone Labs.

[Route 66]

Black diesel oil is normal and a good thing. It means the oil is doing it's job by removing contaminates from the engine.

I would go by the DIC, but changing it early certainly won't hurt anything, especially if it keeps you from freezing.

I'm a firm believer of not using oil analysis to extend oil change intervals. I'll bet that's GM's position also.

[Ray,IN]

Dirk alluded to an important point. GM demands adherence to their oil change interval to fulfill warranty requirements. I did just that until the warranty expired, then went by the computer oil condition advisory. I do think it's important to use the best oil filter available. FWIW, Purolator is #1, Mobil 1 #2. Fram(standard version) dead last. http://people.msoe.edu/~yoderw/oilfilterstudy/oilfilters.html

[Frank P. Martin]

Thanks, everyone, for the replies. Ray- I read the article at the link you provided. Very informative. However, the webpage was last updated in 1999. I wonder how much of it is still applicable in 2009? I've been a subscriber to Consumer Reports for over 30 years and have seen tested products that were top-rated one time and at the bottom the next. Too bad Mr. Knize hasn't updated the webpage with more current information.

If the weather holds, I think I'll change it over Thanksgiving anyway; if only so I won't have to lay in the snow & slush when it's twenty degrees outside.

[diandtom]

I think the GM manual shows changing oil ever 12,000 miles. I change mine at 5,000 miles. I going to be 1,000 miles from my next oil change abd fuel filter change, when we go to Florida in Jan. My problem is should I drive it or changed it before I leave ?

[Frank P. Martin]

Well, I did change my oil today even though I only had about 3200 miles on it. However, it looked much blacker than the oil on 1996 Ford PowerStroke with about the same amount of mileage on the oil.

Changing the oil on a vehicle for the first time is always a learning experience and this one was no exception. Two good things, though. One, this was this is the first time I didn't have to buy a new oil filter wrench. It turned out that the oil filter wrench I had for the old Ford FL-1 will also fit the Delco PF2232 for the duramax. Two, the Duramax takes a gallon less oil (10 qts vs 14 qts) than the PSD did.

I didn't notice that the drain plug was marked "metric" (16mm) until after I took it out, but the 5/8" socket used to remove it seemed to work OK. The oil stream cleared everything until it trickled but then made a mess as it dripped on the skid plate and accumulated to the point where it started dripping off it everywhere.

I thought changing the filter was going to me a messy operation being that it's mounted horizontally so I rigged a funnel under the filter with a hose attached and ran it into the drain pan. However, not much oil seemed to come out when I unscrewed the filter so I guess much of it must have already drained back into the oil pan. On the PSD, this was always an ugly operation because the filter was not quite vertical and, as soon as you untightened it, the oil would run down the sides of the filter and then everywhere. Then you had to remove an oily, slippery filter containing about a half-gallon of oil. I confess that the filter slipped out of my hands several times over the course of ownership, spilling its contents almost always anywhere but in the drain pan.

Refilling- The Duramax gets my vote. The filler is at the front of the engine, vertical, holds a funnel well and easy to pour into when using a gallon jug. On the Other hand, the filler on the PSD was on the valve cover and the funnel sat at an angle. It was also a bit of a reach and low so you had to hold the gallon of oil rather high to pour. This made it prone to slosh out; especially with a full gallon jug.

[Ray,IN]

Frank, I have the same skid plate/oil drip issue. I'm buying a Fumoto oil drain valve for next oil change. The N series has a nipple for using a short hose, but does have limitations you'll read about on the website.
Concerning the oil filter spillage. You can make a small hole in the bottom side with a ice pick or tiny screwdriver, and let it drain into the drain pan if you have the time.Gonna throw it away anyway, right!

[Frank P. Martin]

Thanks for the info, Ray. Is the link correct in your posting? I keep getting a 404 error when I click on it.

This Fumoto might be the answer. It sounds like something that replaces the drain plug and, if so, might provide just enough length for the oil to clear the skid plate. Using the "N" style, you might not need to attach a hose since there is a nipple end which could possibly extend beyond the skid plate.

I thought about just "engineering" something on my own (my inventions come cheap - they're free) to route the oil beyond the skid plate as the initial rush of oil when you unplug it seems to miss the skid plate altogether. However, once the stream subsides, the oil no longer clears the skid plate and begins accumulating on it.

[Ray,IN]

The website changed, sorry. Here is the new site: QuickOilDrainValve.com - the best way to change oil

Checked, this one works.