I just cringe when I think about this

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Apr 11, 2003
Spring HIll
... by running it with the drain plug removed until all the oil comes out of the engine. I wonder what a UOA would look like of the last few drips of oil that spew out of THAT engine.
This topic was batted around recently, but I can't get it out of my head. Do people really do this?
I will sometimes pull the enter electrode from my dist cap and crank the engine a few times to throw off some extra old oil. No load on the engine means no wear issue.
Define "running". As AJ says, cranking the beast with no spark is not likely to cause wear....I mean the oil is the life blood, but if the car couldn't go a few revs at cranking speed without oil, the engine wouldn't last long and your MPG/efficiency would be horrible from internal friction.

I don't always do this, but I have done it in the past with used cars I'm "reclaiming" after a good engine clean. I also use compressed air to get old oil out.
Being a bit rediculous for some, I place a clean knapkin over the oil fill and blow until nothing comes out any longer. This usually gets an additional 1/3-1/2 qt. I haven't run the engine with the drain plug removed, however. To me, it may possibly do more harm than good. My brother-in-law drained the oil, installed a gallon of #1 diesel fuel, started the engine and ran it at idle for a few mins, then drained and refilled, ran for another few mins, then filled with fresh oil. It certainly pulled out the crud! I am not sure of wear it claimed.
There was a guy in a post a long time ago who said that he used compressed air to get all of the last of the oil out of car and truck engines. He even made money doing it. He said that an extra half of a quart or entire quart of oil would come out.
I get the car warmed up (8 miles or so at 55mph) but not so hot that the oil scalds me. Change out the filter, pull the plug and walk away for 30min to an hour. Do something else like clean up the clutter in the garage, or clean garbage out of the car.

By the time I'm done with my other tasks, the oil has stopped dripping. Oh and this is with the car jacked up a bit in the front so I can get far enough under to do the oil change, so the tilt helps get a little more oil out than normal because of the plug location.
First of all compressed air should NEVER be applied to a "closed" crankcase. Seals can be blown out. Most cases aren't closed, but it's a good precaution.

Second, the air should be filtered and somewhat clean. I hope for the sake of your compressor and tools it is filtered, let alone your crankcase.

When I say compressed air - I mean VERY CAREFULLY blowing out the remote filter lines, filter holder, oil cooler line and oil cooler with regulated air. I can get quite a bit of the old oil out this way. Lastly I have blown down the dipstick tube with the filler cap off and I have blown in the filler cap with my hand as sort of a seal. All the above has not been harmful to the car with the result of quite a bit of dirty trapped oil coming out and the new oil staying clean longer.
Probably the most oil remaining is in the oil pump and associated piping. Backfill the oil pump outlet at the filter mount and that may push some of the remaining old oil down into the pan to drain.

I don't see the residual as a big issue. What does it do? If there is half a quart in left in my pan (don't really know) and I put in the 6 qts refill, then it is diluted 7.6 percent. That's like 225 miles into a 3000 mile OCI. No big deal to me. Most of the time my oil will be dirtier than that anyway. I think the residual is insignificant.

I know a guy with a 'vette that lets it drain overnight. Hope he doesn't someday forget and fire that baby up!
Good grief. Change oil on a conservative schedule and you won't have to worry about that last little drop of old oil being left in.

A couple drips worth of 5000 mile M1 mixed in with 5 qts of new M1 will be so diluted why worry about it.

I don't run the engine dry, I don't flush with diesel, nor do I purge the engine with compressed air!!
I seriously doubt that cranking the engine over a little to push out the last bit of oil will hurt the engine. I also doubt it does much good. I find by bouncing the car up and down, I usually get a little more out of some of the dead spots in the engine. I seriously doubt if that is going to hurt, and gives you a look at how good your shocks are.
When an engine has a remote oil filter and an thermostatically controlled oil cooler the amount of used oil left behind can be above "a couple drips".......there are ways to drain these that don't involve compressed air, but can be a hassle. This, of course, does NOT involve the average engine and has zero to do with running the car with no oil.....

PS I always prefill both new oil filters....
Back when I drove school buses, our fleet mechanic told me a story one day. The prior weekend, a friend of his had an oil change done on his Nissan, and the shop admitted they had accidently run the engine for some significant time (I don't recall the details) WITHOUT OIL. Although the engine ran fine, the car owner was understandably sweating about the whole thing. After talking it over with my mechanic friend, they decided to force the issue, or otherwise potentially experience an engine failure some time later at the car owner's expense (rather than at the shop's expense). So they decided to intentionally ruin the engine by running it without oil, and then getting the shop to "fix" their oil change mistake by installing a new or rebuilt engine. In short, it took a lot longer than they anticipated to trash the engine, something like 20+ minutes as I recall.

I'd suggest that engines are a lot tougher than we believe on matters like this. Cranking the engine over a few times without oil (should one feel the need to do so -- I don't)...is a big yawner of a non-event for an engine, in my opinion. Not much different than when you start your ride after returning from vacation.
Anyone seen the infomercials with Prolong where they run the engine around town with NO OIL, only the prolong! Then, they throw dirt in the valves and run it some more! Anyone willing to try this?
Well, lets think about this.

What are you pumping out when you turn the engine with the starter? You aren't doing anything to the oil in the pan. You are pumping out some of the oil which is downstream of the oil pump, in the places that oil most certainly needs to go, like the rod, main and cam bearings, and the rocker arms. You are also scraping the oil film off the cylinder walls.

Is there a load on the engine? No, but that isn't the issue, you had better believe there is a load IN the engine! Try cranking one over with a breaker bar while the plugs are in to see how much load there is! Better yet, grab the flywheel by hand and try to crank it! You are looking at, let's say, 150 PSI in the combustion chamber, which is multiplied at the bearings, because of being absorbed by a smaller area compared to the cylinder volume.

I can't believe that some people would even consider running the oil out of the very places it most needs to be. When you fire a brand new engine, you don't even THINK about it unless it is liberally slathered with oil and assembly lube, and the oil pump is primed.

[ April 15, 2004, 05:35 PM: Message edited by: TooManyWheels ]
It seems to me that in getting every last drop out of systems like the oil pump, oil cooler, etc. all you are doing is making for a longer period of dry starting once the vehicle is refilled with oil and started up.

Unless the vehicle had been severely abused by being way overdue for an oil change I wouldn't even think of trying to extract that last bit of oil.

A better question might be: How many of you take the time to prefill your new oil filter with fresh oil before installing it? This seems like a very good idea for minimizing the period of time when the restarted engine is running without a pressurized oil system.

Best of all would be to use one of the various pre-oiler systems to establish oil pressure *before* starting the engine. I have not gone this far, but I would bet that doing so might be one of the best things a person could do to maximize engine mechanical lifetime.

If one buys that argument that start up wear is one of the top causes of engine wear than it makes no sense to do things which can cause more start up wear.

Agree with toomanywheels. It will do more harm than good so why bother. I would be afraid that the oil pump will lose its prime and you will be running the engine even longer without lubrication. Change the oil regularly and don't worry about it.
I guess the best idea would be a flush fill of El-Cheapo oil inbetween drain and final fill. If I have a car that is more than a quart low upon change, I fill it full and run it before I drain.

[ April 17, 2004, 12:03 AM: Message edited by: Audi Junkie ]
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