flush old oil out with new oil?

[The motor guy]

A buddy of mine had me change the oil in his truck a while back cause he couldn't do it. He told me to take half a quart of new oil and pour it in after the oil was drained and the plug was still out. I never thought, but the new oil I just put in came out black like the old oil. I thought that was interesting and wondered how big of a difference that made flushing out more of the old oil doing that.

Opinions?

 

[Chris142]

I have seen people do that all of my life. I think it's a waste of oil.

 

[JerryBob]

Sounds like a complete waste of oil. You're not thinking that the new oil is getting everywhere in the engine, flushing out the old, right? It's going straight down into the oil pan and out.

 

[02SE]

Pouring a half quart of oil or any amount of oil into the oil fill hole to just let it run out the drain hole, is a waste of oil and time. There is old oil throughout the engine that will only be diluted by new oil, when the engine is run.

You would have to disassemble and clean the engine parts to get all traces of old oil out.

Just change the oil at appropriate intervals, and it will be fine.

 

[ZZman]

If I was that worried about it I'd pour a gallon of kerosene into the motor and let it sit in the oil pan and then drain it.

But I'm not that worried about it

 

[crainholio]

I push a few large syringe fulls of leftover new oil down the dipstick tube after the oil pan has drained. For the 4Runner, I put the vehicle passenger side on ramps front & rear, as the drain plug is on the driver's side. Dipstick is on the passenger (high) side, so oil fed there should flow across the pan floor and maybe help wash any gunk out the drain hole. Or at least push gunk away from the oil pump pickup screen area of the pan.

This is on my project vehicle that was run at 22-25K OCIs by the original owner, and sludge is still being pumped into the filter as shown in the pic below. Here be sludge.

I'm using leftover fractional bottles of whatever 5W-20 or 5W-30 are on the shelf. Can't state conclusively that it helps, but it certainly can't hurt and is only wasting ~75mL of oil.

 

[Bud]

Makes no sense.

 

[Dave9]

Yeah a waste of oil because it gets very little additional old oil out. If for some reason the oil change interval was missed by a long shot, you'd be far better off running cheap oil for 50 miles then changing it again to a quality oil, but if the maintenance was this lax, it seems unlikely this is something the owner would do... more something to do if you buy a car despite it being sludged up and don't want to do an engine flush.

 

[Rolla07]

Yep id agree, waste of oil. Wont change anything.

 

[JeffKeryk]

I heard it works better if you use a quart and a half of Amsoil 0w50.

 

[Dinoburner]

Any engine that is dumping sludge on OCIs should have it`s oil pan dropped and cleaned. Using cleaners is usually counter productive as loosened particles clog the oil pickup screen resulting reduced oil flow.

 

[Snagglefoot]

A.R.

 

[SubieRubyRoo]

Originally Posted by Dinoburner
Using cleaners is usually counter productive as loosened particles clog the oil pickup screen resulting reduced oil flow.


Do you think the cleaners are magically deactivated by oil pickup screens? A solvent-based cleaner like Kreen actually disolves the clumped up carbon chains to break up the sludge, and the oil pickup screen is exposed to some of the higher velocities in the oiling system. The suction and solvent should break anything up.

 

[SWS]

As stated, the fresh half qt is pushing out truly black oil in this engine & lift orientation. Therefore it is at least somewhat achieving the goal of purging old oil. I think we in this community can agree that is a "good thing", however small the benefit (maybe zero benefit).

I have tried this on several of my cars - always got fresh oil out, so no reason to continue.

I wonder if simply sucking the old oil from the pan with a small hand pump through the drain hole would accomplish the same result, without using extra fresh oil.

 

[pitzel]

They used to commonly refer to that as the "Patman flush" around here, modelled after the user, Patman, claiming he did that to his Corvette.

Seems very wasteful. Better long-term results probably would arise from simply doing an extra oil change "the normal way" every 4-6 oil changes, if you subscribe to the theory that more oil changes are better.

 

[Eddie]

My father used to do that with Kerosene.

 

[The motor guy]

I was just doing what he wanted. It seemed like a waste of oil to me too.

 

[Dinoburner]

We can`t know what percentage of chemical flushing is succesful and which isn`t but I do know I`ve cleaned a few screens with fairly solid particles on the screen, all in pre sealed engines. An old time mechanic back in the fifties used a 4 to 1 mixture of fuel oil and 20 wt motor oil with the throttle set screw set to a fast idle for 20 to 30 minutes then drain and fill with 30 wt oil. Engines manufactured up til PVC inhaled a lot of dust etc. It`s always scketchy to loosen the gunk a heavily sludged engine.

 

[Linctex]

Originally Posted by 02SE


Just change the oil at appropriate intervals, and it will be fine.


1,000% correct

I'll add this to my list of "Silly Old Wive's tales about motor oil and engines"

 

[pda1122]

Tell your buddy he can do the whole job then. Don't criticize if you can't do it yourself.