How Long Would You Run 2 or 3 "flush" OCIs When Changing Oil Chemistries?

[garageman402]

I have been told that it takes 3 oil changes to completely remove all traces of a previous oil to get an accurate analysis of a new oil chemistry. In the past I tried running 2 quarts (enough to cover the pickup) & new filter for 20 minutes in the driveway, then drain & repeat for 3 "flushes". The next analysis showed there was still some chemistries from the former oil that is not in the new oil's chemistry. The analyst said I need to do 3 oil changes, & I said I did, but I didn't say I only used 2 quarts for 20 min. each, lol.

LSJ says to run 2 OCI between switching oil chemistries, I'm presuming a full crankcase. My question is how long do I run it? An hour? A day? 100 miles? Any suggestions? I know there's oil trapped in lifters that has to pump out, & maybe VVT plumbing.

 

[CharBaby]

Overkill and a waste of resources. Run a VOA!

 

[Jetronic]

I have been told that it takes 3 oil changes to completely remove all traces of a previous oil to get an accurate analysis of a new oil chemistry. In the past I tried running 2 quarts (enough to cover the pickup) & new filter for 20 minutes in the driveway, then drain & repeat for 3 "flushes". The next analysis showed there was still some chemistries from the former oil that is not in the new oil's chemistry. The analyst said I need to do 3 oil changes, & I said I did, but I didn't say I only used 2 quarts for 20 min. each, lol.

LSJ says to run 2 OCI between switching oil chemistries, I'm presuming a full crankcase. My question is how long do I run it? An hour? A day? 100 miles? Any suggestions? I know there's oil trapped in lifters that has to pump out, & maybe VVT plumbing.

You run a full oci. LSJ said changing the oil chemistry affects UOA results for a full ocoi. That's nothing to worry about except if you do analysis on every change. This is because a large percantage of the old oil remains inside. Let's call it 10% for this argument. after the second change, 90% of that remaining 10% will be gone aswell, so you end up with 1% of the original oil in place.

What also happens is the first oil deposited it's chemistry on the areas of wear, and those don't get stripped in 20 minutes of idling on essentially cold viscous oil.

If it was something to worry about, you should buy all the oil you will need for the life of the vehicle in one setting and never use anything else, even for topping up.

 

[MParr]

Does this idea have anything to do with LSJ’s latest video?
If so, it’s a waste of time, money, and resources.

 

[Patman]

Back in the day when I was switching cars over to GC 0w30 and was interested in seeing the first UOA being closer to 100% GC, I would do what you did and put in 2L of fresh oil and idle the engine. But I would only idle it for maybe one minute. Yes it was a waste of new $12 oil but I was very interested in seeing how GC held it’s viscosity in different engines so having a higher % of it on the first UOA was important to me. These days I haven’t been doing UOAs so when I switch oils in my Honda I don’t do anything differently.

 

[PF52]

If you were closer, I'd be happy to come by and collect some of that 20-minute oil, just to be helpful.

 

[Urshurak776]

Absolutely no need, a waste of time, waste of money and a waste of resources.

Your car will be just fine. Switch and go......

 

[garageman402]

Does this idea have anything to do with LSJ’s latest video?
If so, it’s a waste of time, money, and resources.

Actually, no, this happened 7-10 years ago. I was using Herguth Labs, which was acquired by SGS, they don't do small potatoes like me anymore, lol. Analysts have told me that in order to get an accurate analysis of a new oil you're trying, it's imperative to start with a clean slate, the old oil will skew the analysis. The Herguth analyst is the one who said 3 oil changes.

LSJ does mention it in a video that you need 2 oil changes to completely flush out any residual oil. I've seen the one where he pours a quart through his daughter's car with the drain plug open, that seems a little silly. However, I am OCD enough to let it drain overnight, lol.

 

[garageman402]

Back in the day when I was switching cars over to GC 0w30 and was interested in seeing the first UOA being closer to 100% GC, I would do what you did and put in 2L of fresh oil and idle the engine. But I would only idle it for maybe one minute. Yes it was a waste of new $12 oil but I was very interested in seeing how GC held it’s viscosity in different engines so having a higher % of it on the first UOA was important to me. These days I haven’t been doing UOAs so when I switch oils in my Honda I don’t do anything differently.

So how did the UOA turn out? Did you notice a difference between the first & second or third UOA? In my case the analyst said he found additives (or other chemistries) that are not present in the new oil I was using.

Like you, I haven't been doing too many UOAs lately, either. I bought a 5 pack of kits about 1.5 years ago & just now using them, lol.

 

[garageman402]

You run a full oci. LSJ said changing the oil chemistry affects UOA results for a full ocoi. That's nothing to worry about except if you do analysis on every change. This is because a large percantage of the old oil remains inside. Let's call it 10% for this argument. after the second change, 90% of that remaining 10% will be gone aswell, so you end up with 1% of the original oil in place.

LSJ said 2 oil changes, does he mean the second oil fill is good to go, or 2 changes before you get clean results? As I mentioned, an analyst told me 3 changes are required. I guess by that point we're splitting hairs, & the old contaminant won't affect much of anything.

What also happens is the first oil deposited it's chemistry on the areas of wear, and those don't get stripped in 20 minutes of idling on essentially cold viscous oil.

So how long would you think is necessary to strip that chemistry? Would it be redeposited during the "stripping", as it's being recirculated until drained?

If it was something to worry about, you should buy all the oil you will need for the life of the vehicle in one setting and never use anything else, even for topping up.

Lol, it's not worrying, it's comparing one oil's performance to another. Let's say the copper level is high & I change oils to mitigate that. How will I know it's really working if some of the old chemistry is still in there? Especially when the analyst points that out.

Thanks for the reply!!

 

[ripcord]

I'd just go as long as the voices tell me to.

 

[IndyIan]

I run a full crankcase "flush" for 6-8k miles(10k sometimes if I'm busy for a while), then put whatever is on sale that meets my specs, in for the next flush...
I don't worry about it for my cars, that are running something on the shelf made by shell, pennzoil, or mobil. Maybe if you are running something really really exotic that isn't made by a mainstream manufacturer, you could get into some trouble not flushing all the magic unicorn tears out, when you put snake oil in... but don't do that, and you'll be fine, and save some money.

 

[garageman402]

I run a full crankcase "flush" for 6-8k miles(10k sometimes if I'm busy for a while), then put whatever is on sale that meets my specs, in for the next flush...
I don't worry about it for my cars, that are running something on the shelf made by shell, pennzoil, or mobil. Maybe if you are running something really really exotic that isn't made by a mainstream manufacturer, you could get into some trouble not flushing all the magic unicorn tears out, when you put snake oil in... but don't do that, and you'll be fine, and save some money.

For someone who doesn't "worry about it", you were able to make over 12k posts in 16years about oil....... Maybe you do worry about it, lol.

No tears, no snake oil, just controlled testing

 

[garageman402]

I'd just go as long as the voices tell me to.

Did the voices tell you not to wear crocs?

 

[ripcord]

Did the voices tell you not to wear crocs?

The opposite, but I'm resisting them

 

[demarpaint]

Once I established there is no problems with the engine, eg coolant or fuel mixing with oil, if I change brands I'll sample the third run of the same oil. I think running 2 quarts of oil for 20 minutes as a flush is doing an engine more harm than good, and a waste of good oil.

 

[I<3oil]

I wouldn’t

 

[garageman402]

Once I established there is no problems with the engine, eg coolant or fuel mixing with oil, if I change brands I'll sample the third run of the same oil. I think running 2 quarts of oil for 20 minutes as a flush is doing an engine more harm than good, and a waste of good oil.

That seems most effective, though I'd be inclined to shorten those first two runs just so I'd know quicker. I just want to know how short....

As far as damage due to running the 2 quarts, as long as the pressure stays up (which it did) there should be no damage.

 

[demarpaint]

That seems most effective, though I'd be inclined to shorten those first two runs just so I'd know quicker. I just want to know how short....

As far as damage due to running the 2 quarts, as long as the pressure stays up (which it did) there should be no damage.

Two shorter runs makes more sense to me than running a sump three quarts low assuming it's a five quart sump. Honestly I wouldn't run my car the length of my 100' driveway with two quarts in the sump let alone idle it for 20 minutes. But as always opinions and methods here may differ.

 

[Patman]

So how did the UOA turn out? Did you notice a difference between the first & second or third UOA? In my case the analyst said he found additives (or other chemistries) that are not present in the new oil I was using.

Like you, I haven't been doing too many UOAs lately, either. I bought a 5 pack of kits about 1.5 years ago & just now using them, lol.

The UOAs with GC were always showing lower wear metals in any of the engines that I put them in and it would always hold its viscosity really well too. Then the UOAs following the first one would be very consistent with that first one.