GMCnet: GMCnet => How To Change Your Oil

How To Change Your Oil [message #175798]

Fri, 06 July 2012 16:47

JShot
Messages: 247
Registered: October 2006
Location: NW Ohio

Senior Member

A prospective GMC owner contacted me through the Registry web site with a few concerns and questions. One was about changing the oil. So after I answered him, I thought I'd throw this out to the net for prospective and new owners, and to generate some discussion.

Here's how I told him I do mine:

Warm up the engine, then drain the oil, giving it time to drain well. Pull the oil filter (more on this below). Put on a new filter (no, NOT necessarily a Fram; you could use a Purolator, NAPA Gold, Mobil 1, etc.), and put the oil drain plug back in.

Now put in 5 quarts of oil (your choice, but check the forum for gobs of discussions on this subject!). Run the engine to circulate the new oil, then turn it off and let the coach sit for a while. This gives the oil level a chance to stabilize.

Now pull the dipstick - check it at least twice! Wherever the oil level on the dipstick is showing, this is your new full oil level. Mark the dipstick somehow - file mark, punch mark, whatever.

The front of the oil pan, because of the right side drive axle, has an upward 'depression' in it. And because of this, the front of the pan holds a quart of oil that will not drain out. This is assuming that some PO has not put an oil drain plug in the front part of the pan for draining purposes. If you do not/cannot drain this elusive quart (99% of us cannot), and you put more than 5 quarts back in (because it says it takes 6 quarts for an oil change), you will just - throw out - burn out - get rid of - a quart of oil going down the road. This is especially true if the dipstick (before you marked it) shows that you are a quart low. "Oh, look Maude, I'm a quart low, so I'll add one. Wow, after only 200 miles, I'm a quart low again! Boy, does this thing burn oil!"

No, it doesn't - you're just over filling it! Any questions?

Now, you do know that there's an 'adapter' between the oil filter and the engine block. This adapter has the two oil lines attached to it that go up to the oil cooler section of your radiator. You need to look at these oil lines very carefully. If they absolutely are not new, you need to replace them. Probably the best ones out there are braided SS with the right connections. No, I don't get a kick back from JR.

After you pull the old oil filter, you can see that the adapter is attached to the block with a rather large nut thingy, otherwise known as an "extension" per the diagram (see link below). If you unscrew this thingy, the adapter will separate from the block. On top of the adapter is an 'O ring' of sorts. Actually it is the same sealing ring that is on the new oil filter. So what most of us do is every couple of oil changes, we drop the adapter, pull out the old sealing rubber, and put in the rubber from the old oil filter that we just removed. Most of these "O rings" you will find, are original, and are all hard and cracked, and have never been changed. Some premium filters (Mobil 1, K&N) utilize a captive gasket that cannot be separated. It might just be worth buying a standard oil filter such as an AC Delco PF24, or Fram just to get the gasket - then you can toss the filter. Laughing

Thanks to Bob Burkitt and Rob Allen for the pics and diagrams. Excellent photos By Rob can be found here:

http://www.gmcmhphotos.com/photos/emergency-oil-cooler-line-repairs/p11677.html

And unless you're oil cooler lines mentioned above have not been changed, make sure you carry a socket that will fit the nut thingy, because if you're out on the road, and one of those oil lines ruptures (and you realize it before the engine seizes), you can drop the filter, then drop the adapter, then put the filter back on, directly on the block without the adapter, and be on your way. The socket size is 1-1/4", and a deep well socket works best.

Whew, that's enough typing for now.

HTH someone
Shot

John Shotwell
Ridgeville Corners, OH
78 Royale Center Kitchen
Web Site: GMCmhRegistry.com / Email: john@gmcmhregistry.com

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