It's been said countless times that oil is the lifeblood of an engine. In addition to its primary task as a lubricant (a difficult enough job by itself), the oil also serves to maintain the proper operating temperature for components that cannot be serviced by the primary cooling system, and engine oil is expected to carry away wear particles and neutralize the harmful chemical by-products from combustion gases that escape into the crankcase. Ignore your engine's oil, and you'll soon be facing a variety of expensive failures.

What's more, engine oil is now being used for a variety of actuation duties, such as controlling diesel fuel injectors, adjusting valve timing, or deactivation cylinders. This means that ignoring the condition of one's oil isn't just an issue in the long term; allow the oil to break down, and there can be a variety of drivability, economy, and emissions trouble.

Fortunately, all of these problems are easy and inexpensive to avoid. Sure, it's possible to take your vehicle into one of those quick-change places and get the job done for about the same (or even less!) than it takes to do the job at home, but we actually like getting under our vehicles for a look around once in a while; you never know what problems you may come across. It just so happened that we were able to experience a very real example of this while changing the oil on my '96 GMC K2500.

[Keep reading after the jump to walk through the task of an oil change...]

The first step to properly performing an oil change is to select quality materials. Personally, I like to use AC Delco, Puralator PureOne, or NAPA Gold filters; feel free to check out Russ Knize's oil filter tear-down report and make your own decision. Based on lab analysis of my used motor oil (more on that in a later post), I prefer to use Castrol GTX or Valvoline in my engines. Your results will vary depending on your application; what's more important than the brand is that the correct weight is used, and the correct service interval is observed.

You'll likely need a filter wrench and the appropriate tool to remove the drain plug. For this application, the "cup" style of filter wrench works the best; since I have several vehicles, I write the application on the tool with a paint marker. I also write down the size of the drain plug so that I don't have to bring half of my toolbox under the vehicle. A word of caution if you select this type of filter wrench - different brands of filter may require a different wrench, so beware of that if you don't stick with one particular brand.

The first step in the process is get underneath the vehicle. Some vehicles, such as full-size trucks, are high enough off the ground as to not require any lifting. Other vehicles will need to be raised onto jack stands, driven onto ramps, or placed on a lift or over a service pit. Regardless of the method used, always observe proper safety procedures, and never rely on a jack to support a vehicle's weight.

Next, locate the drain plug. You can see it above on the oil pan (circled in red). It will typically be at or near the lowest point of the oil pan, for obvious reasons. Some vehicles may have more than one oil drain plug, and some vehicles may have nearby plugs for draining other fluids. If in doubt, consult a service manual before proceeding.  

Next, locate the filter. In this case, it's to the left of the oil pan. Since GM decided to run the front driveshaft down the same side, this vehicle uses a 90-degree adapter that moves it up out of the way. This, of course, makes it more difficult to access. A small number of vehicles have remotely mounted oil filters, so it may be located on the firewall or inner fender.

We start off by positioning a catch pan under the vehicle and removing the drain plug. I like to drain the oil when the engine is warm, but not hot. It's no fun to have 220F oil running down into your armpit, and there's no reason it needs to be that hot in order to completely drain from the crankcase.

Although it's not shown here, wearing rubber gloves is not a bad idea as there can be some fairly nasty stuff (such as heavy metals) in waste oil. If your skin comes in contact with waste oil, wash it off as soon as possible.

The oil will come out at a relatively fast rate, and perhaps at an unexpected angle (especially if the stream comes in contact with other components). Be prepared to move the catch pan. Also try to avoid dropping the drain plug into the pan.

Wipe off the drain plug with a clean rag while taking note of any wear particles that may be attached to the magnetic tip. Don't panic if there's a bit of material, but if you notice an increase over several oil changes, it may be wise to have the waste oil analyzed by a lab to see what's going on.

Inspect the gasket (if there is one) for wear, and replace it if necessary. If there is any damage to the threads, replace the plug immediately.

As the oil drains, make sure to keep the pan under the stream, or else you'll have a messy clean-up situation on your hands. If you're doing this outdoors, be aware that wind can whip around the stream as it thins out towards the end.

Expect it to take perhaps 10-15 minutes to drain the majority of the crankcase.

In the meantime, I like to take a bit of fresh oil and apply it to the threads and gasket of the new oil filter. This is also a good time to inspect the filter for any defects, such as a missing gasket, a doubled-up gasket, or damaged threads (problems such as these are rare with a quality filter, but they do happen on occasion). If the mounting orientation of the filter allows, it may not be a bad idea to pre-fill the filter with oil, as this will reduce the amount of time it takes to regain oil pressure during the first start-up (the horizontal mounting of this filter does not allow us to do it here).

You can also take some time to look around the underbody for signs of problems, such as corrosion or fluid leaks. I happened to notice a small amount of antifreeze dripping from the bellhousing bolts. The leak's path led to the upper end of the engine, meaning that I'll likely be installing another set of intake gasket soon (unfortunately, the Vortec V8 used in this truck is known for this problem). Problems like this may or may not be discovered by someone who's being paid to do the job as quickly as possible, which is why we like to do this task ourselves.

Once the oil flow has slowed to a trickle (there's no reason to wait for it to cease altogether, unless you've got more time than we do), wipe off the sealing surface of the pan.

Reinstall the plug. If the threads seem excessively loose, slightly oversized replacement plugs can be purchased. It's recommended that this be done before a problem occurs.

Tighten the plug to the manufacturer's recommended torque, or to "snug". Frankly, we've been doing this long enough that we don't bother breaking out the torque wrench. Waiting for the gasket to touch and then going another quarter-turn or so is probably all that's required; you're not trying to hold the vehicle together with the drain plug, so don't feel the need to use both hands and a cheater pipe.

Now, it's time to remove the filter. Weasel the wrench up into the proper location (in this case, not even light can reach it), and crack it loose. Don't be surprised if it requires some effort, as the gasket tends to adhere itself to the mounting pad over time.

Position rags as necessary to catch any oil that drains from the filter. In this case, we're using a shop rag to keep the oil from hitting the driveshaft and running down to pool in the front differential's skidplate, where it will then leak out over the next several days and leave oil spots wherever the vehicle is parked.

Place the oil filter in the drain pan to empty as much oil as possible.

Wipe off the filter pad with a clean rag, making sure that the old filter's gasket does not remain.

Thread the new filter into place, and tighten it to the manufacturer's recommendations. It's usually suggested that the gasket be allowed to contact, and then the filter is tightened an additional 1/2- to 1 full turn beyond this point. A wrench should not be required for this if you can get a good grip on the filter with your hands. Don't over tighten the filter, or you'll pay the price during the next oil change.

Go back up top, locate the oil fill cap, wipe it off with a clean rag, and remove it.

Take a quick look underneath the fill cap to see if there are any signs of problems. Ideally, it should be clean. The rust-colored deposits here are further signs of the aforementioned coolant leak.

Fill the crankcase with the recommended amount of oil. Once completed, start the vehicle (making sure that adequate ventilation is provided if you're indoors) and watch to make sure that the oil pressure light extinguishes in 5-10 seconds or that the oil pressure gauge comes up (if not, immediately shut down the vehicle and inspect the filter installation). If all looks well, take a peek underneath the vehicle to see if there are any leaks.

There is one final step, and that is proper disposal of the oil and filter. This will vary somewhat by region, but in most areas, service stations are required to take drain oil. Some shops may require a nominal fee for disposal, but many will take it for free as they either sell it to recyclers or use it for heating purposes. You can also see if your area offers waste oil recycling; we have a location only four miles down the road that not only takes waste oil but also will recycle oil filters. The oil can be collected in the original containers; try to avoid milk jugs as they are very fragile and prone to leakage (2-liter soda bottles are a much better alternative). We have a 10-gallon barrel in our garage that's meant for this very purpose, and it's much easier to fill than those little 1-quart bottles.

If filter recycling is not available in your area, then drain the filter of oil for at least 24 hours before disposing of it in the garbage. Go here to find recycling services in your area.