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Readers of this board are invited to check out my blog. It's about my quest to pull 200k miles out of an HT4100 powered '87 DeVille. Am I :cookoo:? Maybe, but show me a Cadillac owner who's normal...

If you have a passion for old Caddies, I think you'll enjoy it. Please feel free to leave your comments or suggestions at the blog or on this board.

http://www.cadquest.blogspot.com

Happy reading!
Steve
 

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After reading thru your blob there are several things you might consider...



The coolant supplement or sealer is actually ground up ginger root....not "tumeric" or whatever you were told. The ground up ginger root stops leaks by the tiny fibers clotting in the leak and expanding when they see the air on the backside of the leak. It works extremely well and is very effective at preventing any internal coolant leaks into the oil. Not just Cadillac, but about every major engine manufacturer installs the sealant in their engines at the factory to guard against any internal leaks due to casting porosities, gasket surface imperfections, etc..... The same company that markets BarsLeaks products makes the GM coolant supplement so it is exactly the same thing. If you find the BarsLeaks products HDC or G12BP it is the same material as the GM pellets. Install it into the radiator hose as you described or directly into the radiator at the radiator cap and never just put the pellets into the coolant recovery bottle.

Based on your description of changing the coolant I would heartily suggest finding a coolant concentration tester and actually checking the concentration you ended up with by filling the system with plain water, draining and then pouring in straight coolant. I suspect you are nowhere near 50/50. Remove the radiator cap and check what is in the system, not the coolant recovery bottle. Good you have the coolant supplement in there, though. That coolant recovery bottle or reservoir by the radiator that you were filling is just an overflow bottle. Coolant pushes into the bottle past the radiator cap as the system heats up and expands and then is sucked back into the radiator when it cools. You should never put anything but premixed 50/50 coolant/distilled water into the reservoir as it will not be mixing actively with the rest of the system.

The correct coolant concentration is extremely important for freeze protection, anti-boil protection and adequate corrosion protection. The coolant needs to be drained and refreshed every 2-3 years at the most to maintain its anti-corrosion protection as that wears out with time.

Ditch the Amsoil and forget the rediculous idea that you can extend the change intervals with their product.

If you really want to go 200K or further on that 4.1 go to the local discount store and find gallon jugs of 15W40 Delo or Delvac or Rotella heavy duty diesel oil and use that. That oil is the closest commercial product available today for what that engine was designed to operate on. Your engine has several high wear areas that need extra wear protection that the current crop of "gasoline engine" motor oils do not really cover adequately. Specifically, your motor has rubbing element tappets (not rollers), it has a heavily loaded distributor gear (that drives the oil pump also), it has rubbing element rocker arms (not roller rockers like current engines) and it has a spur gear oil pump (current engines have gerotor oil pumps that shear the oil less and take less power to drive). The heavy duty diesel oil is much more appropriate for your engine as it has more of the anti-wear additive ZDP in it than anything else you can buy.

Amsoil's claims of extended drain intervals are purely based on their synthetic product having excellent oxidation resistence at high temperatures. IF this were the governing factor in oil change intervals it would be a valid claim, but, unfortunately, it rarely is the reason to change the oil. Oil change intervals are governed by oil contamination with gas/water/combustion byproducts, acid formation, particulate buildup, contamination from dust/dirt in dirty areas, viscosity breakdown, and, yes, oxidation of the oil from high temps.

Your engine will seldom, if ever, see oil temps above 260-270 F even on a summer day with the AC on pulling grades on the expressway. Normally, running down the road on a hot day it will run around 220-230 F. Conventional oil is fine to 305 F. Above that the oil starts to oxidize more rapidly and the synthetic oil has an advantage. Since your oil will never get near or above 305 F there is absolutely no reason to use synthetic oil and it offers no advantage in terms of engine life or extended oil change intervals. Trust me.

Amsoil is extremely costly because of their pyramid scheme of dealers, distributors, salesmen, etc. that all get a cut. They have to convence you to buy it somehow so they use the "extended oil change" interval ploy. Do not believe it. Modern engines with roller elements and gerotor oil pumps can run longer change intervals....but NOT your 4.1. If you short trip it a lot, especially in the winter, I would change the oil every 1500-2000 miles. In the summer and/or with long trips always and freeway driving you can go 3000-3500 miles. General rules of thumb here but you get the idea.

If you use the Amsoil and change at 25,000 like they say do NOT blame Cadillac when the engine takes a shit.


If you REALLY want to protect the engine the next time you are at the GM dealer pick up a can of GM EOS....Engine Oil Supplement. It is highly fortified with the ZDP antiwear additive and is designed for assembly lube and breakin oil. Add a pint to the oil fill at the change and you will have the most anti-wear protection possible. It really isn't necessary if you are using the Delo/Delvac/Rotella heavy duty oil but it does provide more protection.

BTW...as far as Amsoil being "made" in Wisconsin... There is a large warehouse with a bottling line and a blending tank in Wisconsin. All the oil and additives are purchased by Amsoil and shipped in. Nothing is "made" there. They just blend the oil constituents and bottle it. They buy from the same oil and additive suppliers that everyone else does so the idea of them having something special is ludicrous. All the other brands of engine oils are refined and blended in the US also, so there is nothing special about Amsoil being made in the US. Don't misunderstand, Amsoil makes some good products. They are just not any better than anything else out there, they are very costly and they make false claims about their oil being able to be used for drastically extended change intervals. If you continue to use their products, at least stick to the recommended change intervals and buy THEIR heavy duty diesel grades of oil for your 4.1.
 

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If you really want to go 200K or further on that 4.1 go to the local discount store and find gallon jugs of 15W40 Delo or Delvac or Rotella heavy duty diesel oil and use that. That oil is the closest commercial product available today for what that engine was designed to operate on. Your engine has several high wear areas that need extra wear protection that the current crop of "gasoline engine" motor oils do not really cover adequately. Specifically, your motor has rubbing element tappets (not rollers), it has a heavily loaded distributor gear (that drives the oil pump also), it has rubbing element rocker arms (not roller rockers like current engines) and it has a spur gear oil pump (current engines have gerotor oil pumps that shear the oil less and take less power to drive). The heavy duty diesel oil is much more appropriate for your engine as it has more of the anti-wear additive ZDP in it than anything else you can buy.

Since my '93 Fleetwood Brougham has all the above elements, I should probably be using 15W40 in it right? It calls for 5W30 but I've been using 10W30 in it since it was new but there have been a lot of changes in motor oils in the past 12 years.
 

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Since my '93 Fleetwood Brougham has all the above elements, I should probably be using 15W40 in it right? It calls for 5W30 but I've been using 10W30 in it since it was new but there have been a lot of changes in motor oils in the past 12 years.
 

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I had an '85 Deville. Drove her to 238K miles. Then, I switched to my 93 Deville and drove that to 298k miles.

I used Mobil 1 in both.
 

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"The correct coolant concentration is extremely important for freeze protection, anti-boil protection and adequate corrosion protection. The coolant needs to be drained and refreshed every 2-3 years at the most to maintain its anti-corrosion protection as that wears out with time."
I have recently purchased at Wal-Mart and later tested an antifreeze concentration tester made by Prestone. The good thing about this tester (besides the price) is that you can calibrate it yourself by testing small volumes of coolant of known concentrations. I have made 50/50, 45/55 and 55/45. The tester shows (by means of the floating submerged plastic arrow) freezing temps in F and C, as well as boiling points for 15psi radiator cap.
 

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Discussion Starter #8
Thanks to everyone who has checked out my blog, and I hope you'll return for updates now and then. Feel free to leave comments at the blog site as well. Special thanks to Chevelle, who presented on this thread a well reasoned critique of my ideas for preserving this old Caddy, particularly when it comes to oil.

Because of his comments, I undertook a fairly intensive research project into lubricants in general, scouring the college library, the internet, and tapping the knowledge of a wide variety of people. So far, that includes two retired Cadillac mechanics, a GM engineer, and a 20-year lubrication specialist with Ford.

That research has led me to these inescapable conclusions:

1) There is no magic miracle oil. Both Dino and Synth oils have advantages and disadvantages. For me, synth oils just make more sense.

2) Everyone has a strong opinion on what oil is best, and dire predictions for anyone who strays from their line of thinking. Very seldom are these opinions based on science or even personal experience. Quite often people swear by a certain brand of oil only because their dad swore by it.

3) The 3,000 mile oil change interval is a complete fairy tale and always has been, even for the HT-4100.

For these reasons, and a number of others, I'm sticking by my choice to use Amsoil in my Cadillac. I'm not a dealer, nor an evangelist for their products, and I have no intention of getting involved in their MLM scheme. But I have read the science, both Amsoil's and that from several independent labs, and I like what I see.

I also have no plans to try stretching my oil change intervals to 25 thousand miles. If this Caddy gets 7 thousand miles this year it'll be a miracle. Since I have friend who works for an oil lab, I plan to have testing done of the oil condition at regular intervals. I'll post the results at the blog, and here if anyone wants to see them.

This is not the place for an Amsoil vs Mobil 1 vs (insert your favorite brand dino oil here) debate, which is pointless anyway. But if anyone is interested in following a completely independent, and perhaps completely foolhardy test of synthetic oil in a 4100, stay tuned.
 

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I would listen to Chevelle..... and going 25k miles on the oil change is just asking for trouble.

Thats fine if you want to use AMSoil, I personally do not care for AMSoil, but they are not bad. I use Mobil 1 10W-30 Extended Performance in my 4.9, I have since I first got it with 79,917 miles and she now has 111,150miles on her. But do the oil change every 3,000 miles or so, the HT4100 is a finicky engine as it is, and I would try to push your luck by pushing the gap larger.

My '93 has an oil life monitor, even with the Mobil 1 EP (which claims 15,000 miles) I still go by the OLM, it comes out to be just around 5,000 miles between oil changes, which is what I would do anyway. This oil change however, will be atleast 6,000miles because 1,400 miles was my trip from NY to FL, so that steady highway driving was good on the oil.

my Oldsmobile (3800 V6) which has 131k miles gets an oil change every 2-4k miles, depending on driving conditions and when I feel like doing it... most the oil changes were between 3,000-3,500 miles though. That car got regular Mobil Drive Clean 5W-30 (well, they changed it, so Mobil clean 5000 now)

the '79 DeVille (425), well even though I used it as a daily driver, it never accumulated alot of miles on it between oil changes, so the oil was changed every 2,000 miles or so, maybe 3,000 once (I only put 8k miles on that car so far) Plus that engine isn't too clean inside, so the oil got dirty fast.... and I wasn't exactly easy on it either. Actually I ended up changing the oil on that whenever I changed the oil on the Olds or '93, a few times I changed the oil on all 3 cars at the same time, made it easy on myself. The first oil change I used Castrol Syntec 10W-30 (synthetic blend) not because I like it (I don't) but we had it laying around, after that I tried Mobil 1, but the rear main started to leak, so the next switch I used the same regular Mobil the Olds got (bought a big case at Walmart... made it simple) that stopped the oil leak, and I havn't had a problem since.

looking in the oil cap on the Olds, it is kinda sludgy and stuff, the '79 is the worst... but even with 111k miles, my 4.9 is shiney clean inside (I've had both valve covers off) and I believe part of it is from the Mobil 1, but most is from following the OLM and doing consistant oil changes.

I use AC Delco oil filters on all 3 of my cars.
 
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