Orange or Green Coolant for 1991 Chevy K1500 Pickup with 4.3 V6 ?

Hello everyone,
About 7 years ago I flushed out the green coolant in my 1991 Chevy K1500 pickup with a 4.3 V6. The truck now has about 97,000 miles on
it. Normally, I would say stick with whatever coolant came from the factory but the orange coolant seemed like a better choice at the time. I liked the fact that it had a 5 year or 100,000 mile life, and the container said that it was easier on water pumps. It was also ethylene glycol based and seemed to be very similar to the green coolant so I figured why not try it. After flushing the green coolant out, I replaced it with the orange coolant (I think it was texaco) and mixed with distilled water.
My water pump recently started leaking, I don't think it was the orange coolant, just age. I have not had any other problems with the cooling system, but I have recently heard some bad stories about the orange coolant causing head gasket damage, intake gasket damage, and water pump damage, on some vehicles. I've also heard stories about the orange coolant "sludging up" but I have not noticed that problem yet. On the back of dexcool containers, it says the coolant is for use with 1994 or newer vehicles and that on some vehicles (mine was not listed) if you did not change the coolant at least every 2 years, cooling system damage could result.
I'm going to flush the system & replace the water pump, upper and lower radiator hoses, thermostat, and radiator cap. Should I keep using the orange coolant or go back to the green coolant ? I would stay with the orange if I new it would not hurt anything, otherwise in the absence of an answer, I am inclined to go back to the green stuff, providing it won't do more harm than good.
I'm not sure why GM specifies 1994 or newer vehicles and I tend to wonder what the difference would be between a 1994 4.3 V6 & a 1991 4.3 V6 ? Are the seals or metals used different ? That's about the only think I could think of that would make a difference.
Is there anyone out there from a GM service department that knows the answer ? I'm hoping a mechanic or GM tech may be able to answer this question with a reasonable degree of certainty.
Thanks for your help. John
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green ......the orange dexcool was used in some 1994 but mainly 1995 up

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wrote:

There are many opinions out there on the differences between them but the only realy difference is the colorand the that Dexi has a different additive package of organic phosphates. The reason for the shift is in mid 90's engine started to have a lot higher mixed metal content (cast iron and aluminum parts) and their presence in cooling system creates a form of galvanitc reaction between then that the coolant must combat. Dexi was GM's attempt to deal with this while staying at a 50/50 level (to save costs over millions of units a year). Mazda when they shipped their first rotary motor with a aluminum block in 70's shipped them with 90/10 coolant to deal with this. The sludge than builds up is from the reactivity of the coolant with the metals in engine block. The 5yr/100K is a bit misleading because that the ethylene glycol in the coolant never wears out itself the additive package can and galvanic reactivity can cause coolant mixture to become contaminated. The true time this takes varys with engine alloys, driving/tempature cycles and so on (100K of stop and go citty drive is harder on coolant and engine than 100K of highway). I have had no issues at all with Dexi in several vehicles that I have used it in and I am not one to change coolant often either. I do not run 50/50 though as I use at least 60/40 and shoot for around 70/30. This deceases the amount of the reactive agent in coolant (water) and increase the amount of additives by volume in it so reactivety goes down (because of less water) and protection goes up (because more is avaible and less is needed because of reduced water content). I have one vehicle that has seen about 50K miles in last 10 years and has not had a coolant change in that time frame either but coolant is still clean as are tanks and overflow because it has had about a 70/30 mix in it this whole time. When I get a new car one of the first things I do is drain some coolant from it so that I can add more pure antifreeze to it to increases its consentration. Never had a plugged cooling system or sludge problem in 25 years of using 70/30. As a side not I have a 53 year old JohnDeere tractor that I put new coolant in it when I got it 21 years ago and I have no changed it since. It is between 80/20 and 90/10 (because radiators for those old tractors are expensive to replace) and coolant still looks clean and fresh and tractor sees 30 to 50 hrs of use a year bush hogging and other chores and never even thinks about overheating either. Some baulk at high concentrations because they say water cools better but this is a myth because while it does take about twice as much energy to boil off and convert to steam a gallon a glycol, it takes more heat to raise the tempature of it in a liquid state (which we want in a cooling system) and it is densor and weighs more (glycol) It also have a much higher boiling point and lower surface tension which helps it transfer heat out of engine block better so at times the coolant may appear warmer with high consentration of antifreeze but this is because it is removing the heat better and engine temp sensors read coolant temp not block temp. ----------------- TheSnoMan.com
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"John2005" wrote

If I were you, I would just use what originally was in the vehicle. Switching over to dexcool in an engine that had the older green coolant is a waste of time, as you cannot make use of the extended life cycle of dexcool in an engine that has been running the green coolant.
Ian
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Hello everyone,
Thanks for all the feedback guys & thanks for relating your experiences SnoMan. I also agree that going with a little more coolant is probably better than a 50/50 mix. You always need a little water though, as I understand it, pure coolant would not work as well as a mixture of coolant and water.
Ian, my understanding is that as long as you do a good flush am remove the green coolant, then the orange coolant will do it's job regardless of whether or not the vehicle came with green or orange coolant. I did a real good flush on the vehicle before I switched to the orange coolant and that was 7 years ago. When I flush again this time, there should be no green coolant left ( I doubt there was anyway).
As long as the orange coolant won't hurt my gaskets or seals, I think I will just stick with it. Does the orange coolant come in most new vehicles ? Will they likely do away with the green coolants altogether on new vehicles ?
Thanks again guys, John
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"John2005" wrote

Your understanding would be incorrect in this case.
Ian
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