The Sludge Story, It Makes Sense To Me

[68 Ford Stepside]

The Story Of Why Engine Oil Becomes Engine Sludge

By Don Fedak

Fresh engine oil is a clear, free-flowing liquid blend of base stock and additives that contains no fuel, water, coolant, dirt, or other contaminants. In engines that have failed prematurely, the oil has very often been transformed into a high viscosity deposit of brown or black goo, commonly referred to as "sludge."

When regular engine oil changes are neglected, normally free-flowing lubricating oil breaks down, becomes contaminated, ceases to flow, and is transformed into a thick soup of waste products. That’s when serious engine damage is imminent.

Why does engine oil break down, combine with contaminants, and form sludge deposits? Chemistry teaches that engine oil is unstable and decomposes in the presence of oxygen at high temperature. The process, called oxidation, occurs naturally after exposure to normal operating conditions for extended periods of time and is accelerated by exposure to severe operating conditions or to excessively high temperatures. Alternatively, accelerated oxidation may be triggered by a combination of any or all of these factors.

During oxidation, the chemical bonds that define the oil molecules are broken, and some of the reaction products accumulate and interact to form a highly viscous complex mixture of solids, liquids, and gases that contain a variety of solid carbon-based dirt and metallic particles, as well as liquid coolant, fuel, oil and water droplets.

But what can we possibly learn from a sludged engine?

Consider our reliable 40-year-old 10-hp shop compressor that has delivered zillions of cubic feet of pressurized air daily from its ambient temperature shelter. While the electric motor and the V-belts have been replaced twice, the only other routine service this air-cooled V4 compressor has received, other than having the condensed water drained from the tank, is an occasional oil change. When the used, unfiltered HD-30 oil is drained from its crankcase it shows no evidence of contamination or oxidation and looks like fresh oil.

A typical internal combustion engine is just an air compressor in which fuel is mixed with compressed air and then burned. The combustion process generates heat and a variety of reaction products, some of which enter the crankcase as blow-by and contaminate the oil, e.g., fuel, soot, water and other normal reactants, products and byproducts.

Even though the oil temperature is high enough to boil off and extract all the water and other volatile contaminants via the PCV system, this crankcase broth will inevitably change into a deposit that does not drain when the oil is changed. Air-cooled gas or diesel engines are just air compressors in which the engine oil is subject to oxidation because they are exposed to higher temperatures and contamination by combustion products. If the engine is liquid-cooled, the engine oil may also become contaminated with coolant.

Lesson #1: Sludge deposits in internal combustion engines can indicate either stop-and-go driving, lack of proper maintenance, too low or too high an oil temperature or oil contamination.

Sludge formation is not a new problem. In fact, sludge deposits limited the durability of early internal combustion engines. Over the years, oil base stocks were improved, detergent oil additives were developed to keep microscopic sludge-forming solid particles in suspension, anti-oxidation additives were developed to slow the formation of these sludge deposit precursors, and engine oil filters were fitted to remove suspended solid particles from the oil stream and slow the formation of flow restricting sludge deposits on internal surfaces.

Changes in engine oil formulation and treatment accelerated with the introduction of "permanent" glycol-based coolant, another oil contaminant that may accelerate sludge formation. With the recent increased popularity of wet-sleeved engines, as well as the introduction of alternative but incompatible coolants, we are seeing more engine bearing failures.

Lesson #2: Sludge deposits may be due to inferior oil, deterioration of the oil additives or contamination by coolant.

When "detergent oils" first appeared, everyone’s engine repair business increased. Tired, worn out engines, full of sludge deposits because they had always been serviced with non-detergent oils, were ill advisedly transfused with detergent oil, which promptly attacked the sludge deposits. Engine bearing surfaces were flooded with oil containing a high concentration of newly suspended sludge particles. And during the phase-in of detergent engine oils, a number of chemical elixirs for "engine oil desludging" appeared. With current engines, we often encounter similar failures when engines are accidentally overfilled and loosen normally benign engine deposits. Unless you’re very young or your principal residence is a cave, none of this should be news.

Lesson #3: Absence of sludge deposits may indicate the crankcase has been "flushed," especially if fresh oil contains an excessive concentration of solids.

Some years ago we sold some oil, a filter and a pan gasket for a 366 truck engine to a customer who initially was asked to do a routine oil change. He eventually had to remove the oil pan because the engine oil had thickened and would not flow out of the drain hole. Once he removed the pan bolts, the oil pan, very heavy because it was full of thick black goo, fell to the floor. The bozo who had previously contracted to "service" this fleet vehicle had repeatedly neglected to drain the old oil when he changed the filter and topped up the level of the used oil. Exposed to heat for an extended period of time, the old oil eventually oxidized and transformed into a black mass resembling thick molasses or Le Brea tar pits’ crude.

Lesson #4: Always be suspicious of maintenance information.

Today, we see a lot of sludged engines because of two different factors, the trend to ever-higher engine oil temperatures (oil coolers help) and the tendency to neglect or postpone routine maintenance, especially in the case of leased vehicles. When a yuppy BMW owner volunteered that his "Service Engine" light was designed to indicate when he should add some engine oil, I suggested that he might want to change it to read: "Too Late." Engine noises and low oil pressure are obvious indications of inadequate engine bearing lubrication. So, when oil sludge is also found, overextended drain intervals, elevated oil temperatures and/or contamination should be considered as the most likely causes. But there are always exceptions.

Experienced custom engine builders understand that all sludge deposits are not necessarily due to abuse and neglect. When we find a lot of sludge in an engine, we always try to pinpoint the cause(s), do what we can to avoid a repeat occurrence and advise the customer or the installer how to minimize engine sludge formation.

Today, as in earlier times, new and remanufactured engine durability is directly related to the recognition, control and elimination of all factors that support engine sludge formation including, but not limited to, lack of proper maintenance, inappropriate oil temperature, use of an inferior engine oil, and engine oil contamination.

[72greenie]

That was a great read! I learned some things.....thanks!

[kf7mjf]

Good read, thanks for some of the science behind sludge

[68 Ford Stepside]

Times over the years has changed & overall oil is better formulated today than it ever has been. Many years ago when I ran my shop, 99% of the times someone came in with a sludged engine, i knew what kind of oil they were using & how good thier maintenance was. Guy drives with an engine so sludged that most of the oil is in the valve covers or the lifter valley, it is so stopped up it won't drain back to the pan. My first question is do you use Quaker State ? His answer is yes.

Back then if you used Quaker State, you best change the oil & filter every three thousand miles. If you lived in a city & the only place you drove was in the city especially short trips, you best change the oil every one thousand miles. Any oil can sludge, but Quaker State was the worst.

The best oil in those days was hands down Texaco Havoline. The Havoline guy told me once Quaker State oil sludged fast because it had paraffin in it. Havoline came from Texas wells & had no paraffin in it.

[Kurt Combs]

My first job was in a Texaco station at Denman Flats outside Petaluma, CA. We were told that Havoline was the best and I also heard that from the customers. What was always scary was when someone would change from non-detergent to a detergent oil, usually plugged up the pickup screen and starved the engine for oil. Users of that old non-detergent thought it was good oil because it always looked clean, but all the crud would settle in the engine and left it looking like it was fresh. The usual theory back then was if you started with non-detergent, don't switch and stay with one brand. Probably was good advice back in the day.

[ScottT80]

As a kid, my dad always ran Quaker State... until the first engine tear down. It was sludged awful even with regular changes. After years of running it he switched to Castrol. I've since heard lots of horror stories about the Quaker State. I've ran either Castrol or Havoline most of my life.

I know a lot of people are running synthetic now... I hear the same thing about it being bad to switch from conventional oil to synthetic. Leaks, etc.

[70_F100]

Quaker State really got a bad rap years ago, but it did what it was designed to do.

Waaaaayyyyy back in the day, engines were designed without oil filters. Because of this, contaminants stayed suspended in the oil and were carried throughout the oiling system, causing early wear on vital engine components.

Quaker State was one of only a few engine oil producers, and their oil was made from Pennsylvania crude. A couple of other Pennsylvania crude producers were Pennzoil and Wolf's Head.

Quaker State actually formulated its non-detergent oil so that it WOULD create sludge. This sludge attached itself to the engine block. The sludge was comprised of the contaminants that COULD have been suspended in the oil, but by allowing the sludge to accumulate on the block, it was taken out of the oil which resulted in less wear and extended engine life.

In the 50's, partial-flow and full-flow oil filters were introduced. Unfortunately, I guess, lots of the old-timers who had used Quaker State in their older cars continued to use it in their "newer" vehicles. By then detergent oils had been developed which kept the inside of the engine clean and the contaminants were captured by the oil filter. Since the old Quaker State guys had continued its use, engines in their vehicles still had the sludge build-up, whereas engines using detergent oil stayed cleaner inside.

So, Quaker State was not really a bad oil, it was just used improperly and people didn't understand that. Their Super Blend was a mainstay for many years, sold in service stations and auto parts stores by the thousands with excellent results.

In today's world, however, I'm not sure I would want to use it in any vehicle I own!!

[ScottT80]

That would make sense then to some degree why my dad used it then.... I'm sure my grandpa got him started on it. He used it up through the mid 80's.

Theres a lot of heated discussion on some of the other forums about newer oils and their reformulations. Seems the newer stuff lacks zinc. A lot of guys are adding a ZDDP additive. I've been using Valvoline VR1 race oil in a couple of older cars and have been happy with it. Thus far the old Fords have stayed with Castrol though.

[68 Ford Stepside]

That would make sense then to some degree why my dad used it then.... I'm sure my grandpa got him started on it. He used it up through the mid 80's.

Theres a lot of heated discussion on some of the other forums about newer oils and their reformulations. Seems the newer stuff lacks zinc. A lot of guys are adding a ZDDP additive. I've been using Valvoline VR1 race oil in a couple of older cars and have been happy with it. Thus far the old Fords have stayed with Castrol though.

Amsoil has added zinc to some of thier oil, but at $10.50 a quart, i would only use it if i were running a solid lifter engine.

[DuckRyder]

http://www.bobistheoilguy.com/motor-oil-101/

[68 Ford Stepside]

Well, now i've got a headache from reading all that oil info, but i did learn a few things i didn't know.

[68 Ford Stepside]

One thing that i learned is that those two cases of high buck oil that have been sitting in my storage building for six months is going to the bad before i even put it in my engine. Dern!

[wildcard]

I just had my gaskets and some seals changed last week. I always use Quaker State motor oil. The engine has 200,000 miles on it.
My mechanic said to keep doing whatever it is I do to the engine. Said the insides looked stilled look new. I do run a can of Sea Foam through it about every 5,000 miles. Other than that I use only Texaco gas.