Effects from low temp thermostats on engine and oil life???

[Patman]

Al the main reason LT1 owners like to put in a colder thermostat is that these engines run 10.5 to 1 compression and a pretty aggressive spark advance curve, so if you aren't running 94 octane gas, you'll often get power robbing spark retard in the hot summertime. Going with a colder thermostat lessens or eliminates this knock retard, so you end up retaining more of your horsepower.

I still run the stock thermostat in my LT1, because it's my daily driver and I don't feel like swapping thermostats everytime the seasons change. I always let my car cool down at the dragstrip when I'm going for a new best ET, so the coolant temps are always very low to start out on these runs anyways, so I wouldn't see any benefit in a case like that.

 

[Drew99GT]

Why not stick with the stock 180 degree thermostat and adjust the fans to come on a bit earlier than stock? That way you can have a bit cooler coolent temps during the summer but still have good operating temps for wintertime? I also thought the reverse flow LT1 cooling systems did a better job at cooling the engine? It suprised me to hear you were getting up to 220 with a 180 degree thermostat, unless GM still programmed the fans to come on at like 215-220 like they do with most vehicles that use a 195 degree stat.

 

[novadude]

I use a 180 T-stat year round in my 5.0L stang. Stock was 195 deg. To me, I do not know that 15 deg is that big of a deal. With the 180 stat, and the fans programmed to turn on earlier, I know that it eases my detonation problems in the summer months (BTW.. 5.0 Ford's don't have knock sensors, so no retard, it just rattles itself to death). Since I will not change T-stats every season, I guess I will have to live with whatever consequences there may be.

This does not answer your question though... anyone else have any useful input?

 

[jsharp]

quote:

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Originally posted by Patman:
Al the main reason LT1 owners like to put in a colder thermostat is that these engines run 10.5 to 1 compression and a pretty aggressive spark advance curve, so if you aren't running 94 octane gas, you'll often get power robbing spark retard in the hot summertime. Going with a colder thermostat lessens or eliminates this knock retard, so you end up retaining more of your horsepower.

I still run the stock thermostat in my LT1, because it's my daily driver and I don't feel like swapping thermostats everytime the seasons change. I always let my car cool down at the dragstrip when I'm going for a new best ET, so the coolant temps are always very low to start out on these runs anyways, so I wouldn't see any benefit in a case like that.

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The GM engines must be different than the Ford 5.0L's It seems like most of the guys who tried low temp thermostats in stock or almost stock Fords ended up going back to stock thermostats once they noticed their ET's suffered or became inconsistant. Not to mention the fuel mileage going into the dumpster...

[ October 23, 2003, 03:03 PM: Message edited by: jsharp ]

 

[novadude]

quote:

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It seems like most of the guys who tried low temp thermostats in stock or almost stock Fords ended up going back to stock thermostats once they noticed their ET's suffered or became inconsistant. Not to mention the fuel mileage going into the dumpster...

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That is true of 160 deg stats. 180's work nice in 5.0's. However, I will agree that the ONLY improvement I saw from a 180 stat was the fact that it'll ping less on those 90 deg days.

 

[Alex D]

Yeah, I had a Ford 5.0 once and for a winter beater now have a thunderbird with the 4.6
All of those Fords run cooler than the Corvette ......I had 180F thermostats in both of them and took them back out cause they're way to cool for the winter here in the Midwest ..... lot's of condensation under the oil filler cap, even on long hauls!! And in the summer they did not make a difference because on both Fords the radiators limit to keep coolant to the thermostat temperature was at around 80 degrees ambient temperature. After that the coolant temp would rise with the ambient temp, a good indication that the capability limit of the radiator was reached (Both cars also had brand new radiators).

[ October 23, 2003, 03:19 PM: Message edited by: Alex D ]

 

[sbc350gearhead]

I have a 160 in my truck, and have had it in there for several years. No mileage change, no driveability change. According to most engine experts, 160's will make the engine hot enough to burn off condensation. The only reason I have mine is because of my hypertech programming.

 

[jsharp]

quote:

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Originally posted by novadude:

quote:

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It seems like most of the guys who tried low temp thermostats in stock or almost stock Fords ended up going back to stock thermostats once they noticed their ET's suffered or became inconsistant. Not to mention the fuel mileage going into the dumpster...

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That is true of 160 deg stats. 180's work nice in 5.0's. However, I will agree that the ONLY improvement I saw from a 180 stat was the fact that it'll ping less on those 90 deg days.

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Now you have me wondering. My 5.0L is stock except for an K&N drop in and Flowmasters and I've ever noticed it pinging using 91+ octane fuel with the stock thermostat. I think I'll start listening a little better on hot days...

 

[novadude]

Mine is a '95. 94/95 cars are notorious for thier pinging. The 94-95 EEC calibration was completely different from the earlier cars. When it was above 90 deg, with stock timing (10 deg) and stock EEC, my car would ping even on 93 octane. Everything on the car was in perfect tune, and it still had this problem.

Wideband O2 readings from dyno sessions have shown the 94/95 cars to be real lean. This is the real problem. I had a well know tuner fatten up the fuel curve a bit, and he suggested turning on the fans a little sooner.

When I installed the custom chip he burned, I noticed that the fans were running A LOT, even in 30 deg weather. Turns out he dropped the low speed fan setting to 195 deg. With the stock T-stat, this did not work. Rather than get a reburn, I dropped down to a 180 stat. All is well, and my detonation is gone.

If your car is an 87-93, you probably have no worries.

Man, did we hi-jack this poor guys thread!

 

[jsharp]

quote:

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Originally posted by novadude:

Man, did we hi-jack this poor guys thread!

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Agreed. Sorry Alex!!

 

[Patman]

quote:

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Originally posted by Drew99GT:
Why not stick with the stock 180 degree thermostat and adjust the fans to come on a bit earlier than stock? That way you can have a bit cooler coolent temps during the summer but still have good operating temps for wintertime? I also thought the reverse flow LT1 cooling systems did a better job at cooling the engine? It suprised me to hear you were getting up to 220 with a 180 degree thermostat, unless GM still programmed the fans to come on at like 215-220 like they do with most vehicles that use a 195 degree stat.

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That's exactly it, the second of the two fans doesn't kick in until 227F! So when I'm stuck in traffic or moving slowly, it doesn't take long for the coolant to get that high. When moving along at highway speeds, the coolant is always in the 190-200 range though. It's just that with the front of my car having no rad opening, it's a bottom breather, so in order to get good airflow into the rad, you need to be moving. So on really hot days, even with both fans going full speed, it is hard to get the coolant temps down fast. Turning on the AC does turn on the second fan right away, but you'll still see high temps in the summer with the AC on when you're idling in traffic.

The reverse flow system is not quite all it's cracked up to be.

 

[sbc350gearhead]

The reverse flow cooling system is designed to keep the heads cooler. The normal operating temp of the coolant, is about the same.

[ October 23, 2003, 05:11 PM: Message edited by: sbc350gearhead ]

 

[Dr. T]

Great post.

A friend of mine with just noticed that his temp. gauge would DROP from normal as he was driving indicating that his thermostat was stuck open. He reported severe hesitation all the time, especially pronounced during abrupt throttle down acceleration.

He took it in to a mechanic who...get this, did an OIL ANALYSIS!! My kind of mechanic! In either case, the report showed a high amount of fuel dilution in the oil.

 

[Patman]

quote:

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Originally posted by sbc350gearhead:
The reverse flow cooling system is designed to keep the heads cooler. The normal operating temp of the coolant, is about the same.

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True, but one problem with reverse flow is also that it's hard to get all the air out of the system, which also makes it less efficient sometimes.

 

[Alex D]

Dunno.....we have the 96 Vette with the LT1, an 01 T/A with the LS1 and an 02 Suburban with the 5.3.....The LT1 with the low temp thermostat and also being a bottom sucker never gets over 200 F coolant temp even in 90F weather when the A/C is on and both fans are running. I never have problesm keeping the car cool, even in the summer.

I also never had problems refilling and burping the system, but I have a trick to do it that seems to be making the difference.......always do it on ramps with the front end up, reconnect all hoses, but leave the thermostat housing open and refill the system carefully watchign for teh moment the fluid appears in the thermostat housing. Keep filling very slowly until it is clear full and then replace and toghten the thermostat. this way the entire block is filled with a minimal amount of air, maybe even none at all. Then I complete the proceedure by refilling the reservoir and doing the revving thingy. Done. After warming the engine to operating temp and cooldown overnight the car sucks less than a pint from the overflow showing that I had the system almost full the first time around.

quote:

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Originally posted by Patman:

quote:

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Originally posted by sbc350gearhead:
The reverse flow cooling system is designed to keep the heads cooler. The normal operating temp of the coolant, is about the same.

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True, but one problem with reverse flow is also that it's hard to get all the air out of the system, which also makes it less efficient sometimes.

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[ October 23, 2003, 09:17 PM: Message edited by: Alex D ]

 

[Alex D]

I am currently running a Hypertech 160F thermostat in my LT1 Corvette. Usually the coolant temp is around 175 to 185F and the oil temp around 175 to 195F.
What are your opinions on these temps for oil and engine life?
Does anyone with a low temp thermostat have done UOAs to see if there are effects on wear.
A lot of discussion goes around on the corvetteforum in regards to low temp vs. the normal 180F thermostat on the LT style engine. Keep in mind that the LT engines always run coolant temps at least good 15F higher than the thermostat rating!!

 

[Al]

I suppose there is a reason that folks have lower temp thermostats and perhaps there is a special reason for using on on the LT1.

But in general a low thermostat is not a good idea. It will allow the engine to run at lower efficiency, cause more combustion chamber buildup and negatively affect economy. Also the vehicle will probably have higher moisture in the oil causing quicker deterioration of oil and more iron products.

The thermostat will allow the engine to run cooler only on days and only under conditions when the outside air temp and load on the engine is low enough to allow that to happen. But people are under the mistaken impression that in the heat of summer with a/c on the car will run cooler. Actually that will not happen bc in those cases the cooling is dependent on the cooling capacity of the radiator.

 

[Alex D]

Al, thanks for your comments. I do have to say though that switching from the 180F stock thermostat to the 160F the overall temperatures of engine and transmission have decreased by about 20F, even in 90F ambient temperatures. I have in two years now never seem temperatures over 200F, whether in city traffic or on the interstate (with reprogrammed fans of course). Before and with the 180F thermostat my Vette used to always run in the 210 to 230 oil temperature range, ATF was in teh 210 range and coolant also right around 210 to 220F. SO the colder thermostat does actually allow the car to run cooler if the cooling system is in good shape. I think often the effect of the low temp thermostat gets hidden by a not so good cooling system or dirty radiator (especialy on the Vette).

quote:

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Originally posted by Al:
I suppose there is a reason that folks have lower temp thermostats and perhaps there is a special reason for using on on the LT1.

But in general a low thermostat is not a good idea. It will allow the engine to run at lower efficiency, cause more combustion chamber buildup and negatively affect economy. Also the vehicle will probably have higher moisture in the oil causing quicker deterioration of oil and more iron products.

The thermostat will allow the engine to run cooler only on days and only under conditions when the outside air temp and load on the engine is low enough to allow that to happen. But people are under the mistaken impression that in the heat of summer with a/c on the car will run cooler. Actually that will not happen bc in those cases the cooling is dependent on the cooling capacity of the radiator.

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