Engine Sludge

[Dan D.]

This is a question probably for Duke or Joe but certainly anyone can comment if they want.

The awful sludge deposits in the rocker boxes and around valve springs that were so common to see in yesteryear are all but gone now. I have always thought this to be caused by the quality of the oils back then and to some degree because engines did not have PCV.

In talking with a gentleman this past weekend he believes that leaded gasoline was the biggest contributor. I have not heard this before, but instead of arguing I chose to be ignorant - thus I keep my mouth shut rather than possibly saying something wrong.

So the question is - does leaded gas contribute to sludge buildup?

Thanks,
-Dan-

[Duke W.]

Re: Engine Sludge

Better detergents/dispersants, higher resistance to oxidation, and PCV systems are why modern engines rarely generate sludge, and PCV systems were a big factor. My SWC never developed any significant sludge, which I attribute to a good maintenance schedule and the PCV system since oils back then were not nearly as robust as today, particularly in terms of oxidation resistance.

There have been some cases of engine sludge on certain engines in the last few years - I recall Chrysler and maybe Honda - that resulted in recalls, and I attribute those cases to short trip driving, probably exacerbated by a less than optimum PCV system design.

Leaded fuel has no significant effect on sludge formation, but TEL resulted in more rapid buildup lead oxide deposits in the combustion chambers and on spark plugs back in the day. They are the white deposits that could also be seen in the tailpipe if the carburetor wasn't excessively rich.

Leaded gasoline also had so-called "lead scavengers" - mostly bromides that would combine with lead to form lead bromide, which is a gas, but some lead also reacted with oxygen to from the white lead oxide deposits.

The world is full of myths, misinformation, and old wives' tales.

Duke

[Bill W.]

Re: Engine Sludge

In my high school days (65 ,66,67,) I worked at "service stations" I call them service because we had to check oil , tires , and wash windows including pumping .$0.25 cents a gallon gas . Most of our customers only changed oil filters every other oil change . I'm sure that had something to do with sludge . As I recall I only added oil in my cars because it didn't last long enough to make sludge.

[Stuart F.]

Re: Engine Sludge

I have been using MaxLead 2000 (TEL) for many years in my original 63 L-76, and have been tipping it even a little more now that I regularly use only 90 Octane non-ethanol gas. I change my oil/filter at least twice a year and adjust my valves every couple of years. Each time I have marveled at how clean it is under my valve covers. I last changed my plugs probably in about year 2000, or about 10k miles ago. Yesterday, I overprimed the engine for my Sunday morning drive and it stumbled for awhile after start, but cleared out fine. Took my usual drive where I am able to get in a few WOT runs and I let it wind to redline in 1 st and 2 nd (don't usually go beyond 5500 otherwise - you know, save the rods) and it ran very smooth and pulled strong as usual. I credit the plug life to my electronic ignition which has saved me from a lot of skun nuckles over the years changing plugs. I remember in particular my 58 fuelie engine back in the day - load it up in traffic and you could bet on fouled plugs good for no more than 5500 rpm.

Stu Fox

[Steven B.]

Re: Engine Sludge

In my high school days (65 ,66,67,) I worked at "service stations" I call them service because we had to check oil , tires , and wash windows including pumping .$0.25 cents a gallon gas . Most of our customers only changed oil filters every other oil change . I'm sure that had something to do with sludge . As I recall I only added oil in my cars because it didn't last long enough to make sludge.

Bill, I had not thought of it in years but I worked in a station in that time frame and some of our customers also changed filters every other oil change. When we adjusted valves we always wiped the inside of the covers and the head to remove any sludge. When I had to keep the filter I would remove it and drain it. One guy saw me do that and complained it was a trick so he would have to pay for an additional quart of oil. He thought mixing new with old was OK and cheaper. He also complained when he wanted a price on a new tire. He had 15" wheels but wanted a price on a 14" because we were trying to sell him a larger tire that cost more money. Steve

[Dick W.]

Re: Engine Sludge

Bill, I had not thought of it in years but I worked in a station in that time frame and some of our customers also changed filters every other oil change. When we adjusted valves we always wiped the inside of the covers and the head to remove any sludge. When I had to keep the filter I would remove it and drain it. One guy saw me do that and complained it was a trick so he would have to pay for an additional quart of oil. He thought mixing new with old was OK and cheaper. He also complained when he wanted a price on a new tire. He had 15" wheels but wanted a price on a 14" because we were trying to sell him a larger tire that cost more money. Steve

I can remember the day when you would pull the valve covers off and there would be a perfect shape of the valve cover over top the valve train. On some of these cars I know it was not from lack of service as we had a leasing company and adhered to a strict maintenance schedule. You could almost tell what brand of oil was used in some of those cars, Pennsylvania crude based oils seemed to build more deposits that asphaltic based crudes. Today, I am not sure you could buy an oil that would not keep your engine clean if properly changed.

[Jim L.]

Re: Engine Sludge

In the "for what it's worth" category:

I have an un-rebuilt '57 265 engine for which I know the maintenance history back to 1960. There is no sludge in this engine.

From 1960 through 1966, it had an oil and filter change with detergent oil every 1000 miles.

From 1967 until it was taken out of service in the early '80s, oil and filter were changed every 2000 miles, still with detergent oil. The engine has approximately 105K miles on it.

FWIW......

Jim

[John F.]

Re: Engine Sludge

I have been changing my own oil & filter every 2000 miles since 1964 as a believer in preventative maintenance with Valvoline. Might be overkill. Never any sludge buildup.

[Martin M.]

Re: Engine Sludge

Engine sludge is also an indicator of an overheated engine.

[Joe L.]

Re: Engine Sludge

This is a question probably for Duke or Joe but certainly anyone can comment if they want.

The awful sludge deposits in the rocker boxes and around valve springs that were so common to see in yesteryear are all but gone now. I have always thought this to be caused by the quality of the oils back then and to some degree because engines did not have PCV.

In talking with a gentleman this past weekend he believes that leaded gasoline was the biggest contributor. I have not heard this before, but instead of arguing I chose to be ignorant - thus I keep my mouth shut rather than possibly saying something wrong.

So the question is - does leaded gas contribute to sludge buildup?

Thanks,
-Dan-

Dan-----


I think the biggest factor in the elimination of sludge is the vast improvement in the formulation of motor oil that has occurred over the years. The elimination of lead may have had an effect, too, but I expect it's quite minimal. However, the elimination of lead has had many other positive effects on engine longevity. Lead was good for octane and valve seat lubrication but bad for just about everything else in the engine and the fuel system.

[Joe L.]

Re: Engine Sludge

Engine sludge is also an indicator of an overheated engine.

Marty------


Yes, and that's one of the benefits of using synthetic motor oil-----it will withstand much higher temperatures without "cooking" and generating sludge.

[Jerry W.]

Re: Engine Sludge

Remember the slogan " Bardall does it again"

[Bob H.]

Re: Engine Sludge

Not to say chev had any issue but poor engine design can also cause sludge, ex my 1999 Lexus with 34,000 miles. Got a call from the service manager saying I needed to come down to see what I had done by missing one oil change. No exaggeration, 2" of pure sludge under the valve cover and a shot engine. After being denied warranty coverage, I split the cost of a new engine. Months later and after doing research (the internet can be a wonderful thing) I discovered this had become a common problem, hence major class action lawsuit by many and got my money back. Seems the oil return holes were too small and the oil was collecting on top and being cooked.

[Timothy B.]

Re: Engine Sludge

When I was a teenager I remember servicing a 1963 F-600 dump truck in my Fathers shop that had a 292 V-8 engine. This was before PCV was used on these engines so it had a road draft tube, the engine oil was Dryden 30wt. they bought in 55 gal. drums.

My chore was to adjust the solid tappets and I remember the sludge build up inside the valve covers because I had to clean them and install new gaskets. I also remember when that truck went to the Ford dealer for brakes one winter and the service manager installed a PCV valve and the smell and sludge went away, huge difference.

[Jerry K.]

Re: Engine Sludge

I remember my first car, a 1950 chevy. I'd put a dollar worth of gas and fill it up with oil.