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  #61  
Old 01-11-2018, 11:43 AM
Doug Eves Doug Eves is offline
 
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Actually any oil that finds it's way into the combustion chamber will tend to add to combustion chamber deposits as the additives won't get completely combusted. This is very minor as next to no oil should be getting in there and some of the unconsumed additives will go out the exhaust. Lead is in the fuel and if you ever flooded your engine (i did on every hot start) then yes, lead gets in the crankcase. Also on initial startup the in complete combustion also puts some there along with a minute amount during normal operation. This lead needs to be removed by the oil which this type of oil will do. As far as temps go, the local temps on the immediate surface of the cylinder will be quite hot in any engine water cooled or not. Same with the temps of the layer of oil between the bearings and rod journals for instance. The local temps there are EXTREMELY high. High enough for thermal cracking to occur. The results of this can be seen in viscosity degradation and possibly coke production. I have never measured any significant visc degradation in use of up to 60 hrs. Oil always met new oil specs. Oil will remove any coke as well as incomplete combustion material. Synthetics won't thermal degrade however and are more lubrisc. I wouldn't mix the two.
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  #62  
Old 01-11-2018, 12:59 PM
BillL BillL is offline
 
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Originally Posted by Doug Eves View Post
Same with the temps of the layer of oil between the bearings and rod journals for instance. The local temps there are EXTREMELY high. High enough for thermal cracking to occur.
So just how high do you think the bearing temperatures are? The highest known temps are around the piston and heads, particularly under the piston crown, over the top of the heads around exhaust ports and valve guides. And the oxidation viscosity increase is primarily due to time at temperature of the oil sitting in a high temp sump. Specifically, high power (BMEP) diesel engines.

My experience says the peak oil temps in the bearing flow is not extremely high, but know that the crank pin metal temps are higher than the rods. I don't remember the numbers precisely, but oil temperature rise across the bearings (main and rod) are well under 50 degrees F.

Oh- one other question, how does/do the current Mobil 1 formulation(s) compare to the XD3?
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  #63  
Old 01-11-2018, 05:13 PM
Doug Eves Doug Eves is offline
 
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Hi Bill.... I just had to call one of the R&D oil experts from work to revisit. Highest temps are indeed around/under the piston. He said temps have been measured (somehow) as high as 350 celius in some engines. Mineral type base oil can get sheared a bit between the bearing and shaft but the thermal oxidation is happening up where you said. He also said that the "coke" deposits i have seen stuck to the engine parts gets produced as some oil gets past the rings, gets burnt and then gets scraped back down into the bottom where the oil has to absorb it. That's where this XD3 oil shines as it can put all that sludge into solution and keep it from falling out on the engine parts. Some oils can't perform that function. He also said that Delvac 1300 super is the same just a different name. Also said they have synthetic version which is even better.
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  #64  
Old 01-12-2018, 12:18 PM
lr172 lr172 is offline
 
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Originally Posted by rv7charlie View Post
Doug,

I don't think anyone is expecting the oil to clean lead from the combustion chambers. But the synthetic av oil fiasco a while back seemed to be related to lead building up throughout the engine because the synth oil failed to hold the lead in suspension so it could be drained. I'm assuming that the lead got there because of blowby in our sloppy-loose a/c engines, but I could be wrong. About the whole thing.

Anyway, the question in my mind is whether Rotella or similar auto oils will act like av oil in this respect.

The other issue I've seen raised is the elevated head temps of our air cooled a/c engines, as opposed to water cooled engines. No issues along those lines?

I run mogas almost exclusively, so the lead issue is minor for me, but the head temp issue remains.

What about mixing dyno & synthetic auto oil? Dyno for rust protection; synth 'cause it's super slick....

Charlie
I run rotella in my Porsche. It is an air cooled boxer engine, very similar in design to a IO-540. Aviation oils have no design features specific to air cooled engines. I would run the Rotella in my IO-320 if I had confidence that it could hold the lead in suspension as well as the aviation oil with it's AD additives. Not saying it doesn't, just no one has told me it does. Diesels have to carry a lot of junk in suspension, but it is not lead, so I remain a bit skeptical.

I will also add that everyone calls our engines "loose" relative to auto engines. However, when I rebuilt my 320, the clearances were pretty much the same as the old Chevy 350's that I rebuilt for my boat. Granted, contemporary engines are likely a bit tighter than the old Chevy small blocks. The ring end gaps appear much larger, but that it due to the odd duck, choke bore. once you account for the taper, it is about the same .030" used in naturally aspirated auto engines. The gap has to be increased as combustion temps increase, but this is unrelated to air or water cooled.
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Last edited by lr172 : 01-13-2018 at 11:12 PM.
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  #65  
Old 01-13-2018, 01:24 PM
Doug Eves Doug Eves is offline
 
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Ir172....One further comment around what I have seen. Originally when I started analyzing my oil at work the technician doing the testing came to me wide eyed with the lead concentration coming back off scale high. This normally would indicate bearing material in the oil. I told him that I was burning av gas. So every time I changed the oil it came back the same. I had him actually quantify it through dilution to get the reading on scale for his calibration curve.It came back at 4020ppm. I think the oil is removing the lead. Also I have seen lycomings with 1000 hrs apart that had used this oil and they were absolutely spotless. So if lead was hanging around and depositing I sure couldn't see any.
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  #66  
Old 01-13-2018, 11:06 PM
lr172 lr172 is offline
 
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Originally Posted by Doug Eves View Post
Ir172....One further comment around what I have seen. Originally when I started analyzing my oil at work the technician doing the testing came to me wide eyed with the lead concentration coming back off scale high. This normally would indicate bearing material in the oil. I told him that I was burning av gas. So every time I changed the oil it came back the same. I had him actually quantify it through dilution to get the reading on scale for his calibration curve.It came back at 4020ppm. I think the oil is removing the lead. Also I have seen lycomings with 1000 hrs apart that had used this oil and they were absolutely spotless. So if lead was hanging around and depositing I sure couldn't see any.
Thanks for the data points here Doug. Good to see some historical experience with this oil. I may do some experimentation with the Rotella or Delvac 1300. Would avoid the excessive costs of aviation oil, mostly due to shipping costs for me.

Larry
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  #67  
Old 01-14-2018, 06:45 AM
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Sam Buchanan Sam Buchanan is offline
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Originally Posted by lr172 View Post
Would avoid the excessive costs of aviation oil, mostly due to shipping costs for me.

Larry
Just as a datapoint, I purchase Phillips 20W-50 aviation oil from vendors on *Bay and it is ~$75/case delivered to my door. Quality auto oil is going to cost about this much at the local auto parts store.
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  #68  
Old 01-14-2018, 07:53 AM
lr172 lr172 is offline
 
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Originally Posted by Sam Buchanan View Post
Just as a datapoint, I purchase Phillips 20W-50 aviation oil from vendors on *Bay and it is ~$75/case delivered to my door. Quality auto oil is going to cost about this much at the local auto parts store.
I also pay $75/case. However, at the local menards, a quart of Rotella 15W40 is only $3.50. They used to sell gallons for under $12.00, however, they only seem to stock the 10W30 in gallons now. This is about half the cost.
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  #69  
Old 01-14-2018, 09:48 AM
rv7charlie rv7charlie is offline
 
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Doug, and Gasman,

The Esso and variants don't seem to be available here in the USA deep south, but Shell Rotella is everywhere. I just started looking at it, based on this thread, and discovered that there are several variants, from basic dyno to synthetic blend to full synthetic, and single weight to multiweight.
http://rotella.shell.com/products.html
Which type do you think is best in a Lyc, and would you pick single weight or multi weight? 'T', T-1, T-4, T-5, T-6? Is Aeroshell 100 (50 weight) heavier than Rotella 40 (are the weight scales the same)? Is 15w40 'thick' enough for the Lyc that's been fed a diet of Aeroshell 100?

I'm not sure of the significance, but Shell's product pages only seem to mention gasoline engines in the 'T-6 Multi-Vehicle' oil description. Any significance to that, or is it just marketing?

Thanks for educating. :-)

Charlie

Last edited by rv7charlie : 01-14-2018 at 09:52 AM.
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  #70  
Old 01-14-2018, 11:05 AM
lr172 lr172 is offline
 
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Originally Posted by rv7charlie View Post
Doug, and Gasman,

The Esso and variants don't seem to be available here in the USA deep south, but Shell Rotella is everywhere. I just started looking at it, based on this thread, and discovered that there are several variants, from basic dyno to synthetic blend to full synthetic, and single weight to multiweight.
http://rotella.shell.com/products.html
Which type do you think is best in a Lyc, and would you pick single weight or multi weight? 'T', T-1, T-4, T-5, T-6? Is Aeroshell 100 (50 weight) heavier than Rotella 40 (are the weight scales the same)? Is 15w40 'thick' enough for the Lyc that's been fed a diet of Aeroshell 100?

I'm not sure of the significance, but Shell's product pages only seem to mention gasoline engines in the 'T-6 Multi-Vehicle' oil description. Any significance to that, or is it just marketing?

Thanks for educating. :-)

Charlie
Hopefull Doug will input, but from my research, you only want the variants spec'ed for diesel. I used the Rotella T 15W40 (labeled as Rotella T Triple protection). That is a diesel oil and you'll see SPI specs like CI-4, CJ-4, etc. Avoid any that don't have diesel specs. Diesels need additives to hold soot in suspension, like our lead, and the automotive gas engines don't need to hold that much in suspension, relative to diesels. I would avoid their multi-vehicle variants. Only the heavy duty diesel oils. I would be suspicious of any of the oils that are 10Wsomething, as diesels don't usually spec that low.

100 aviation oil is a 50 weight oil. However, I don't see why a good quality 40 weight oil. like 15W40 wouldn't survive just fine in our application. Lot's of folks use 80 aviation oil, which is a 40 weight oil. A 20W50 oil is probably only providing a 45 weight viscosity after 50 hours anyways.

Larry
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Last edited by lr172 : 01-14-2018 at 11:13 AM.
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