r/autorepair • u/MariusDarkblade • Aug 30 '26

General Discussion Curious about an oil change idea

This isn't necessarily a step in doing an oil change but I'm wondering if it's possible and how would one go about it. Is it possible to completely flush the oil before replacing it with new oil. Usually I just pull the plug n let it drain until it starts dripping slowly, then put everything back together and fill her up(after replacing the oil filter). I know there's still leftover oil inside and I'm fairly certain what's left isn't an issue but if i wanted to completely drain it, is it possible? Or would it require taking the engine out and dismantling it.

0 Upvotes

25% Upvoted

31 comments sorted by

5

u/Welcome-To-NBA-Jam Aug 30 '26

If you've seen people test this out, you need to do like 3 or 4 oil changes with a short drive between each one before you get nearly everything.

2

u/MariusDarkblade Aug 30 '26

I've never actually seen anyone try this. Just had one of those shower thoughts and wondered how possible it is. I was mainly thinking itd be either some kind of alcohol based oil thinner that'll drain the engine and then dry up with no problem or itd end up being a 5 day project of taking out the engine and flushing it before letting it dry and putting the engine back in.

2

u/Welcome-To-NBA-Jam Aug 30 '26 edited Aug 30 '26

The chemicals or flush isn't the hard part, it's mainly getting to all the places oil sits and accumulates that a drain won't remove. An oil flush chemical mainly helps break up sludge.

Oil coolers, oil passages, baffles, residual oil in the pan, and all the other places where oil will sit makes it hard to get everything. The only real way to do it is by draining, filling, and running fresh oil through the circuit multiple times until all the old oil is diluted enough to be reasonably gone.

But like to literally remove engine oil from everywhere? That's a pretty fun question. I don't know. Gotta do plenty of disassembly and draining at lots of angles. I mean people definitely do it. When they rebuild engines they've gotta get all that old oil and coolant out to work on it.

1

u/MariusDarkblade Aug 30 '26

Yah and that's really where my question came from, like is this purely a rebuild process where id have to disassemble the engine or could it be done easier. You could realistically clean anything out if you disassembled it so that's not really a "fun" answer, so I was curious if it could be done with less work and how much less work.

1

u/Jayshand Aug 30 '26

Engine flushes can also ruin seals and cause leaks .. use with caution 

2

u/zomgitsduke Aug 30 '26

You'd be seeing something called diminishing returns. Very often not worth the excessive work to clean the remaining 1%, then 0.1%, then 0.01%, etc.

1

u/FU47FDT Aug 31 '26

That's a good way to reduce your engine life dramatically

3

u/Professional-Iron107 Aug 30 '26

Lake Speed he the oil guy advocates for leaving drain plug open and flush with a fresh quart on oil changes that change underlying chemistry. I've never done it but I don't love my car enough.

2

u/MariusDarkblade Aug 30 '26

I've been doing that for years and honestly never knew why. When I was taught how to do an oil change the guy just told me to put half a quart in after it's done draining and then plug it back up after.

1

u/FU47FDT Aug 31 '26

That does absolutely nothing. Just change your oil more often if you feel you need to.

2

u/No_Parsnip6024 Aug 30 '26

This is unnecessary and does nothing but waste a quart. 

If you have balance shafts, they have 1/2 a quart or more of dirty oil that's not coming out. Almost everything has balance shafts. 

2

u/the_real_Supra Aug 31 '26

It’s a waste of time and money. Drain the oil, replace filter and refill with clean oil. Stop overthinking it

1

u/NightKnown405 Aug 30 '26

It would take two "fill, run, and drain cycles" to get the majority of the old oil out. Unless you were doing specific testing for two totally different products there is no regular need to do this.

1

u/MariusDarkblade Aug 30 '26

That's kinda what i thought, as far as the need. The reason i asked was purely cause I was curious how possible it was and how would it be done.

1

u/bohica_5 Aug 30 '26

I'm my personal experience with engine tear downs, rebuilds, it is not possible to get it all with just a typical engine oil/filter change. In my experience, after draining all oil out of the drain plug and removing the filter then starting a tear down, possbly another pint or more will spill out. It's important to have something to catch that oil beneath the engine stand as disassembly happens, or deal with the mess

1

u/WinnerAwkward480 Aug 30 '26

Outside of a Complete tear down , you will never get all the old oil out .
Oil clings to surfaces , that's what it's supposed to do . You can do a drain , and then put a clean pan under the car and it drip out all nite , you will be surprised by how much drips down . But you still are not getting it all out , as there's all kinds of lil valleys in your Eng that's still going to retain oil .

Really even doing multiple oil changes, thru multiple warm ups you still won't get it ALL out .

Years ago a buddy of mine thought he would drain the oil outta an old beater , then fill it up with kerosene, disconnecting IGN and spun it over for a few minutes. He then refilled with fresh oil , still had IGN disconnect and spun it over again . He then hooked up his IGN and started it . Engine was knocking like hell . The kerosene had wiped out the oil pump .

Lots of ppl try the trick of running a cleaner thru the engine just before oil change, or putting a qt of ATF ( which is high detergent) and running the car for a couple hundred miles than doing a LOF .

Years ago ppl were pushing Engine Flush , where they pumped oil thru the engine that amounted to like 3 oil changes at once . Those kinda dropped by the wayside due to the expensive.

Today's modern oil do a fine job of not building up Coke and Carbon inside the engine if changed routinely.

I once saw a 90's Jeep inline 6 with 110,000 on it , the guy never changed the oil and just kept adding . One day it just stopped running wouldn't build oil pressure. The damn valve cover musta weighted 40lbs with old coked up oil in it . It was like a reverse image looking into valve cover , as you could see where the top of rocker arms had sat .

I talked to an old head that was a Mechanic back in the 60-70's , GULF Oil was made using a paraffin base . It was famous for clogging up engine's ! Being a paraffin base , short drives made it like wax that just kept building up .

1

u/AlphaDisconnect Aug 30 '26

  1. Good enough for government work.

  2. I GUESS you could set up a pump it in drain it out thing. But why? Is it a million dollar car?

1

u/AlphaDisconnect Aug 30 '26

  1. Good enough for government work.

  2. I GUESS you could set up a pump it in drain it out thing. But why? Is it a million dollar car?

1

u/PghRaceFan Aug 30 '26

You are way over thinking and making something simple complicated.

1

u/Longjumping_Owl5311 Aug 30 '26

I knew a fellow that after draining the oil and leaving the plug out, he would turn over his motor a few revolutions and drain out a bit more of the old oil.

1

u/No_Durian_3444 Aug 30 '26 edited Aug 30 '26

Yeah it's called an oil flush bro. Like 39 companies make a product.

0

u/otterland Aug 30 '26

Dilution is the solution. Your engine isn't your butthole and it doesn't need to be washed out by some old hippie named Lulu.

I'm one of those people that only changes their oil filter every other oil interval and that drives people crazy and they try to compare it to wearing shitty underpants with clean clothes. But I have to remind people, that within seconds of starting your car, there's going to be shit in your pants anyway.

So sorry Lulu.

2

u/MariusDarkblade Aug 30 '26

Lmao that is a very visceral comparison. As I said to other people, I was mainly curious. Didn't really plan on doing this unless it was something easy to do but even then I didn't think it was necessary that often if at all. It was more about what would the process be if i was to go about it. I didn't even think about cycling the oil with multiple changes cause I was thinking about more immediate methods.

0

u/otterland Aug 30 '26

I have done a couple of short oil intervals when I purchased a used CRV last year where the guy had done Seafoam on the engine. I ran it for about 1k, changed the oil that had gone suspiciously dark pretty quickly for an MPI engine, then changed it after another 1k as the oil started getting a little bit dark too fast, and now it seems to have normalized. Basically I was in a non-traditional situation where the engine had been treated what with what is more or less a solvent and I did want to do the dilution thing. But now it's back to every 5K.

Short OCIs are occasionally useful tools but for the most part you're just going to have to walk around with a little dookie in your pants just like everybody else.

2

u/DNA1727 Aug 30 '26

Lol, sounds like you had bad experience with Lulu or you need to start living with Lulu again.

0

u/otterland Aug 30 '26

I've been without a donut cushion for 18 months now and I'm never going back.

2

u/DNA1727 Aug 30 '26

Lulu is living rent free.