UOA on engines consuming oil, longitudinal data

W72

Joined
May 19, 2023
Messages
8
Oil geek post.

I've read these:

https://bobistheoilguy.com/forums/threads/oil-consumption-vs-not-doing-oil-changes.367695/



Blackstone says that adding a quart or more extends OCI several thousand miles. They show graphs of their many UOA results, but they don't have the 'good data'. Good data would be longitudinal: one person with a burner sending in multiple oil samples in-between oil changes, for example sending a sample in every time just before they add a quart.

Anyone here carry that out? What were your results?
 
When the head gasket really started to leak, it had been a few years since I changed the oil on my truck. It doesn't get many miles, but with it cycling through an oil change every ~500 miles or so, I didn't see a reason to change it.
 
When the head gasket really started to leak, it had been a few years since I changed the oil on my truck. It doesn't get many miles, but with it cycling through an oil change every ~500 miles or so, I didn't see a reason to change it.

Did you happen to send in samples for UOAs ?
 
I do 4k/6month oil change intervals (whichever comes first) on my 4 vehicles, and none of them consumes any oil. The kind of analytical data I wish was available could allow us to tie the likelyhood of a car becoming an oil burner with increased oil change intervals.
 
The kind of analytical data I wish was available could allow us to tie the likelyhood of a car becoming an oil burner with increased oil change intervals.
That'd be good too, though I'm still hoping someone with an engine that consumes oil will report on what they found for multiple UOAs in between oil changes.
 
I do 4k/6month oil change intervals (whichever comes first) on my 4 vehicles, and none of them consumes any oil. The kind of analytical data I wish was available could allow us to tie the likelyhood of a car becoming an oil burner with increased oil change intervals.
There’s just too many factors.

I can tell you that I owned a 1999 Honda Accord for 17 years 289,000 miles. Purchased new, 3,000 mile oil changes using conventional. By the time it reached 280,000 miles it was consuming around a quart every 1,000 miles, and then it increased to a quart every 500 miles. Mostly highway driving, very little city driving in all those 17 years.

I can also say that I owned a Lexus LS 460 for five years, mostly 5,000 mile intervals using synthetic. Tried two 7,500 mile intervals on that car at around 100,000 miles, then switched back to 5,000 mile intervals. Mostly highway commuting, very little city. Started consuming oil at around 100,000 miles, maybe a quart in 5,000 miles, then 1.5 quarts at around 120,000 miles. At around the 150,000 mile range it began consuming around two quarts in 5,000 miles. Then at around 170,000 miles it became a full fledged oil burner, using a quart every 500-700 miles. Got rid of it with 179,000 miles on it, 5,000 mile intervals (except twice), mostly highway commuting. Shorter intervals didn’t save either car, but then again, I did put some serious miles on both.
 
There’s just too many factors.
If not propspectively designed, it'd be a mess for sure, but nothing that couldn't be controlled for with some preplanning. There have been taxi-cab studies talked about here in the past. I'd be happy just to hear results from individuals on the UOA benefit of repeatedly adding oil to a burner between changes. Blackstone says it has a significant positive impact, but it'd be great to hear from someone with an engine that consumes oil will reporting on what they found for multiple UOAs in between oil/filter changes.
 
I had a 1978 f250 that went through a quart a day (100 miles) of super tech 20w50. After a while of not doing an oil change, it developed a sticky lifter. I changed the oil and it went away and never came back.
 
If not propspectively designed, it'd be a mess for sure, but nothing that couldn't be controlled for with some preplanning. There have been taxi-cab studies talked about here in the past. I'd be happy just to hear results from individuals on the UOA benefit of repeatedly adding oil to a burner between changes. Blackstone says it has a significant positive impact, but it'd be great to hear from someone with an engine that consumes oil will reporting on what they found for multiple UOAs in between oil/filter changes.
So, you’re talking about something different, right? Not, how potentially longer intervals may/may not add to oil consumption, but what adding oil to an engine that consumes oil over an interval will do to UOA results, right?

And I would say it would help those results (on paper). I’d think the TBN would be higher, the viscosity would stay within parameters better, etc. And I can see why...you’re replenishing the additive pack with fresh oil.

Right now, I have a car that really doesn’t use oil, but previously I have. And I always assumed me dumping a quart or two into it along the way replenished the oil.
 
So, you’re talking about something different, right? Not, how potentially longer intervals may/may not add to oil consumption, but what adding oil to an engine that consumes oil over an interval will do to UOA results, right?

Correct. For example an engine that consumes a quart every 1000 miles. After a complete oil change, send in samples for UOA every 1000 miles (at 1k, 2k, 3k, 4k, 5k, ... miles) until the report contains a recommendation for a complete oil change. So send in samples Mostly I'm interested in results from a burner. Leaker results might not be very interesting.

And I would say it would help those results (on paper). I’d think the TBN would be higher, the viscosity would stay within parameters better, etc. And I can see why...you’re replenishing the additive pack with fresh oil.

That is what the Blackstone newsletter said. But it didn't report longitudinal data such as the kind I'm looking for.
 
What would be even more interesting is what would happen in you add a bypass oil filter.
Especially if it was valve seals as well and not just excessive blowby.
 
I had a 1978 f250 that went through a quart a day (100 miles) of super tech 20w50. After a while of not doing an oil change, it developed a sticky lifter. I changed the oil and it went away and never came back.
Assuming about 12 mpg, you were running a 33:1 blend. (y)
 
Blackstone says that adding a quart or more extends OCI several thousand miles.
Without knowing anything about chemistry, If my sump was 5 quarts, I burn 1 quart, so I add one new quart (20% of the sump) is it not reasonable to assume I have extended the life approximately 20%.

The fly in the ointment is you don't know what your starting % was, and all the contaminants are still in the sump - there just dispersed by 20%.

This isn't much different than a transmission drain and fill, except the drain part, which in addition to refreshing a percentage, it also removes the same percentage of contaminants?

If this math doesn't work with chemistry, then I apologize.
 
Assuming about 12 mpg, you were running a 33:1 blend. (y)
12 mpg? I wish! It was more like 7-8, though I did get 10 mpg on one tank. It was actually coming out of the seals because the pcv hose wasn’t hooked up. Once I fixed that it was back to regular oil usage.
 
and all the contaminants are still in the sump

Maybe, or maybe not. Probably some, probably not all. Probably some types, probably not all types. The series of UOAs that I propose would answer that. Which contaminants are flushed out of the system through the exhaust? to what extent? or which get trapped in the sludge?
 
Maybe, or maybe not. Probably some, probably not all. Probably some types, probably not all types. The series of UOAs that I propose would answer that. Which contaminants are flushed out of the system through the exhaust? to what extent? or which get trapped in the sludge?
Would you? If you just did a UOA without adding, you would figure out how many contaminants / how used up the oil is at that point. All that stuff stays there, then you refresh / dilute with the new oil, so you would be back to whatever spot you were at that percentage of the oil ago that you just added.

Running successive UOA after each top up doesn't really change anything unless the wear / use pattern is significantly non linear based on the oil's condition at that point?

Or is Wear / use significantly different depending your point in the cycle?
 
Top