Leaded fuel / oil compatibility? Aviation oils?

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Hello everybody. I'm hoping to learn more about oil issues for my specific application since frequent internet searches and even an e-mail to an oil manufacturer returned mostly opinions and marketing. I'm running a small block Chevy with a roller cam. The engine has 13:1 compression and cranks 250 psi on the gauge. I run leaded 110 octane fuel. I had been using Mobil 1 High Mileage 10W30, thinking the higher ZDDP content would be helpful even if not totally necessary since I have a roller cam, but upon tearing the engine down for a freshening, I found evidence of corrosion inside the engine particularly on the connecting rods. The bottoms of the pistons had some crystalline material baked onto them. I did some internet research and found some discussion of issues with synthetic oil not being able to hold the lead halides formed during combustion of leaded fuel in suspension, and that the lead halides are corrosive and can lead to the type of damage I saw inside my engine. I e-mailed Mobil 1 hoping to get a response from an engineer, but all I got was a one liner from some marketing type who said was, "Sure, Mobil 1 will work fine in your application, go ahead and use it!" I do not know of any modern oils that are designed for use with highly leaded fuel except aviation oils, but I don't know anything about ashless dispersant oils and their use with a high compression racing engine. Any reasons why running Aeroshell 15W50 would be a terrible idea? Could I add a ZDDP additive to the Aeroshell oil to help with cylinder wear? What about the new Aeroshell Sport 4 stroke oil? Does anybody know what viscosity that oil is? Any other possible oils out there that might be able to handle the lead? Thanks! Joe
 
Lead halides?? They are fairly unstable. No, leaded fuels don't affect motor oil very much. The 'OLD' Penn. based oils handled the lead very well. Your motor will like it too. John--Las Vegas.
 
Instead of changing oils, why on't you change to an unleaded fuel? I'm sure Rocket or Sonoco could recommend you an appropriate product.
 
Remeber with tetraethyl lead, dibromoethane was put into the fuel to convert lead oxide, produced in combustion, into lead bromide which was very volatile and went out the tailpipe. Without the dibromoethane, the engine would have clogged up with lead oxide, a white solid (used also as pigment in lead paint). The lead bromide would then react with moisture to reform lead oxide and hydrobromic acid. This would happen in the exhaust system and resulted in rusted out mufflers and tailpipes. It sounds as though your engine is suffering from the acidic effects of all of this.

Arew you running the vehicle on trips to get it fully warmed up? Where are you getting leaded gas? Aviation gas? It may not be formulated to burn correctly in your engine. Will Sunoco Hi Test run OK as suggested by The Eric? In the old days, lots of folks added MMO to fuel to keep the engine clean from lead deposits and still do in aircraft engines that burn the leaded fuel.
 
Joe:

Sounds like you have an aluminum rod drag racing engine. You probably ran it a few seasons if you are freshening it up, and sounds like no street driving.

Are you using standard purple fuel?

Any additives like propylene oxide?

Do you run a crankcase evacuation pump?

Do you have a really serious windage control system, maybe a crank scraper?

As far as using the standard leaded race fuels, I doubt that is the issue. They have excellent additive and anti-oxidation packages.

Give us a little more information.

Also, dont go to a heavy oil if this is a drag race engine that does not get the oil ip to 160-180F before launch. The oil pressure will be way too high on cold oil.
 
I did forget to ask the basic questions:

Have you always used Mobil 1 and no other oils?

Have you used any oil additives?

What size oil pan?

Do you change the oil on a frequent basis?

How did the top of the pistons look?
 
The engine is a 383 sbc used for drag racing. It's a one piece rear main seal 90's stock block machined for splayed billet main caps. The rods are 4340 nitrided. I have run several different brands of 110 race fuel including Sunoco, VP, Renegade, and Turbo Blue depending on what's available at the different tracks. The engine was designed for 105 octane fuel or better with a MON of 100 or better, so changing to unleaded fuel would be a problem since all the 100 octane unleaded fuels have a motor octane number lower than 100, usually around 95. Running on 93 octane pump gas would of course be out of the question detonation-wise. I have not run any fuel additives or nitrous. I have been considering adding a GZ motorsports crankcase vacuum pump but have only run a draft tube vent from the right side valve cover so far. When the motor was new I used Quaker State 10W30 non-synthetic oil for the first season, and then switched to Mobil 1 and only used that from then on. I don't have a crank scraper and am using a Milodon 5 quart pan. Before racingI run the engine long enough to get the water temperature up to 180 degrees but I don't have an oil temp gauge. I change the oil at the end of the season. The tops of the pistons had small amounts of lead deposits but looked normal. There was a substantial amount of gray crud baked onto the bottoms of the pistons however - up to 1/8" thick. The bearings looked fine, but the rods were actually covered with a light coat of rust. The car did sit all winter without being run, and was only fired up once prior to the tear down. During the rebuild I installed lighter weight forged pistons and had thermal barrier coating applied to the tops of the pistons by Swain Tech, but the original hypereutectic pistons did not have any coatings. The exhaust pipes are usually white on the inside after running, and the oil turns lighter and cloudy, not black, as run time accumulates. From my previous experience with running leaded fuel, that color in the oil is normal. I am thinking at this point that the oil does not get hot enough during the passes to boil off any accumulated moisture, and without a vacuum pump the moisture stays inside the block, combining with the lead halides to form acid.
 
Pyro, I think your last sentence hits it on the head. With leaded fuels, you need to get everything to full operating temp and keep it there for a time to get the chemistry working in your favor. This ensures that the volatile lead bromides (halides) are volatilized out of the oil and don't sit in the engine slowly releasing acid.
 
I am trying to be open minded, but your ideas on TEL causing acid and corrosion are not likely the cause. We had 74 years of successful leaded fuel usage before it was off-road only in 1995.

It's likely the engine/car sat outdoors over a spring/winter and just had some moisture condensation events without fresh oil.


From the EPA website:
Leaded Gas Phaseout

Air Quality Fact Sheet

June, 1995



Leaded gasoline will no longer be available in the United States after December 31, 1995.

The Clean Air Act Amendments of 1990 mandate the elimination of lead from all U.S. motor fuel by January 1, 1996. This
represents the final step in a gradual reduction of lead in gasoline since the early 1970s. "Regular" gasoline typically
contained approximately 4.0 grams of lead per gallon; average lead content was reduced to 0.5 gram/gallon in 1985, and
still further to 0.1 gram/gallon in 1986.

"Unleaded gasoline" is allowed to contain no more than 5/100ths of a gram of lead per gallon.
 
I do appreciate everyone chiming in and trying to help me with the corrosion problem. Yes, I agree it could be solved in other ways than by using different oil, such as by running the engine for longer periods to keep moisture boiled off, adding a vacuum pump or pcv system, or changing the oil more often. I admit I may not have phrased my question properly in the original post. My intent here was to learn more about the "black art" of the oil end of this equation.

The reason I got my ideas on lead halides and corrosion was not only from other anecdotal reports of similar issues other hot-rodders had when using PAO synthetic oil with leaded fuel, but also from the following quote from a technical article from the Experimental Aircraft Association.

"Lead bromide, when mixed with water, metals, and lubrication oil, produces a corrosive liquid very damaging to engine components... The presence of water and the corrosive properties of the lead bromide are always lurking to damage an engine. This lead bromide by-product is just one of the reasons why aviation lubricating oil is different from automotive lubricating oil."

Now of course I am well aware that leaded fuel was used in automotive applications for years with no ill effects; however automotive oils today are much different from the oils of yesterday, and while suspension of lead by-products and neutralization of acids produced would have necessarily been a feature of yesterday's oils, today it is not even on the mind of oil engineers as they formulate oils for whatever demands today's modern cars put on oil. The API SM/ILSAC GF-4 issue with reduced ZDDP content in today's oils is a case in point of oil manufacturers not factoring backwards-compatibility with yesterday's technology into the mix of modern oil.

I am interested in how, chemically, aviation oils are different when it comes to being designed with leaded fuel in mind, and if any niche-market racing oils might also be designed similarly. Also I would like to learn more about whether ZDDP is necessary at all for engines without a flat tappet cam. For instance, if I did choose to experiment with running aviation oil and accepted the small loss of horsepower that would result from the higher viscosity, would there likely be any negative effects from the lack of ZDDP? And if so, could ZDDP possibly be added to the oil without destroying whatever beneficial properties the aviation oil had in the first place? I am hoping that Bob is the Oil Guy might be the place that someone with experience in the chemistry of lubrication might be able to answer these questions. Thanks again.
 
Aircraft oils aren't known for their ability to prevent corrosion. Many an otherwise good aircraft engine has had to be rebuilt because of corrosion. I don't see any benefit of considering an aircraft oil at all.

I think an HDEO with their higher TBN would be a move in the right direction. You might also consider something like the Amsoil motorcycle oils, which are formulated with high levels of corrosion inhibitors.

Ed
 
Sounded like a race engine,, how was the wear? I agree with the use of an HDEO oil ,you can't get a better oil and the price is right so you will change the oil often without worrying of the cost. IMO getting the lead out of the fuel was the best thing for engine life that was ever done.
 
@Steve - The piston rings were pretty beat, but aside from the rust on the rods and the junk on the bottoms of the pistons, everything else looked about brand new.
 
Last edited:
Originally Posted By: Pyro_Joe
I do appreciate everyone chiming in and trying to help me with the corrosion problem. Yes, I agree it could be solved in other ways than by using different oil, such as by running the engine for longer periods to keep moisture boiled off, adding a vacuum pump or pcv system, or changing the oil more often. I admit I may not have phrased my question properly in the original post. My intent here was to learn more about the "black art" of the oil end of this equation.


I really dont think there is any "black art" involved here. Oil is still oil whether it was refined 16 years ago in the leaded era or in 2011. Yes the distilled base quality is better and the additives have changed, but it's still the same basic product produced in the same ways. If you could spend just one week at a refinery, you would see how simple and basic the refining and blending process is.

Originally Posted By: Pyro_Joe

The reason I got my ideas on lead halides and corrosion was not only from other anecdotal reports of similar issues other hot-rodders had when using PAO synthetic oil with leaded fuel, but also from the following quote from a technical article from the Experimental Aircraft Association.

"Lead bromide, when mixed with water, metals, and lubrication oil, produces a corrosive liquid very damaging to engine components... The presence of water and the corrosive properties of the lead bromide are always lurking to damage an engine. This lead bromide by-product is just one of the reasons why aviation lubricating oil is different from automotive lubricating oil."


This sounds like a mix of retoric, antedotal information and twisted common sense to me. If you mix water and (name a substance) in your oil, sure, youve got a problem. Also, where did anyone get the idea that lead(II)bromide and chloride is corrosive? Please provide a link. I believe they are confusing this with Bromine which is very toxic and corrosive.

Anyone remember their exhaust whiting out after a road trip? That was the lead bromide and chloride lining the inside of the exhaust. Certainly not particularly corrosive. If it were, your exhaust system would be the first thing to let you know.

The hard black crust on the spark plug electrodes, lead oxide. Lack of lead put the tune up shops out of business, thankfully.


Originally Posted By: Pyro_Joe

...oils today are much different from the oils of yesterday, and while suspension of lead by-products and neutralization of acids produced would have necessarily been a feature of yesterday's oils, today it is not even on the mind of oil engineers as they formulate oils for whatever demands today's modern cars put on oil.


TEL does not produce any acids in it's decopmosition.

(CH3CH2)4Pb + 13 O2 → 8 CO2 + 10 H2O + Pb
 
I'm wondering if you can convert this engine to run on E85 - it has a rating of 105 octane, doesn't it?

Fuel might be easier to find as well, then.
 
Two diffrent metals and moisture= galvanic corrosion. Back when we used leaded gas spark plugs and exhaust systems didn't last very long. spark pluks would get fouled from the lead and exhaust systems would start rusting out in a few years. In the 60's it wasn't unusual to see a three year old car needing a new muffler. some people would drill an 1/8th incch hole at the rear bottom of thier muffler to let the moisture out.
 
Remember that Mobil 1 "AV=1" oil was a total failure due to the problems with suspension of lead. While I run Avgas 100LL in some of my personal lawn and yard stuff, with Mobil 1, I don't know if there is any corrosion due to the lead.

One thing to consider is Camguard. A product specifically designed to eliminate internal engine corrosion. From my very basic borescope exams of our aircraft fleet, it seems to work very well.
 
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