Does an engine run cooler with Syn in it?

[BuickGN]

Originally Posted By: SlugGunner
Hi, I'm new to these forums but have been an automotive tech for 50+ years and retired as an ASE-CMAT (Master Tech) in '94. I'd like to clear up a misunderstanding on the 'purpose' or the THERMOSTAT in modern auto engines.

FIRST, it DOES NOT control or regulate engine temperature in an engine. It is only a part of the TOTAL COOLING SYSTEM used in automotive applications. The THERMOSTAT's main purpose is to bring the engine operating temperature to NORMAL OPERATING TEMP as quickly as possible. It does this by REMAINING CLOSED until it's minimum (starts to open) termperature is reached. This contains most of the heating coolant within the engine block and preventing its circulation thru the radiator portion of the cooling system until this temperature is reached. This temperature is usually 295 degrees F on most modern gasoline engines.... this has been determined to be the minimum desired operating temperature for effective emission control purposes. This is also normally the minimum temperature at which the ECM control system goes into "CLOSED-LOOP OPERATION".

Most modern liquid-cooled engines maintain a normal operating temperature in the range of 210-230 degrees F. Once the THERMOSTAT opens, it has LITTLE FUNCTION unless the coolant temperature drops below its rated temperature rating (195^), at which time it will begin to close and raise the temperature of the coolant in the engine block again. During the NORMAL OPERATING TEMPERATURE RANGE the coolant temperature is mainly controlled by the RADIATOR, TYPE OF COOLANT MIX/RATIO, RADIATOR COOLING FANS and AIR FLOW ACROSS RADIATOR FINS. Ambient air temp and humidity also have an effect in both HEATING and COOLING.

Hope this helps clarify this issue.

But, to get back to the subject of this discussion.... yes, it is possible for synthetic oil to lower engine tempertures. Mainly, this is seen in OIL TEMPERATURE (especially if you have an OIL TEMP GAUGE). I have seen this be as much as 30-40 degrees COOLER difference in racing applications. It has also given WATER TEMPERATURE GAUGE INDICATIONS of 10-20 degrees COOLER at the same time and conditions. Outside ambient air temperature and humidity can CHANGE THIS EFFECT CORRESPONDINGLY.


I think you meant 195 degrees. The modern cars I've dealt with run right on the thermostat. My TL stays at 194 and has very, very little varience.

My GN stays right on 160 all the time unless I run it hard and then it comes back down to 160 very quickly. I have my fans set to come on at 165 degrees.

On many, the cooling fans dictate at what temp it runs which is what I think you were saying. The thing is, every one that I've seen will heat up to a preset temp, the fans come on, it cools quickly, they shut off, and it starts all over again. Where does a cooler oil temp help this?


I'll say again that the only way cooler oil will affect coolant temps is if the cooling system is marginal already.

I just so happen to have an oil temp guage on the GN and did not see a difference in the short time I ran synthetic. I believe it happens in oil temps but maybe since mine runs a huge cooler already the difference wasn't there.

I'm sure the OP was talking about his water temp, most cars don't come with oil temp guages.

 

[SlugGunner]

Originally Posted By: SlugGunner
Hi, I'm new to these forums but have been an automotive tech for 50+ years and retired as an ASE-CMAT (Master Tech) in '94. I'd like to clear up a misunderstanding on the 'purpose' or the THERMOSTAT in modern auto engines.

FIRST, it DOES NOT control or regulate engine temperature in an engine. It is only a part of the TOTAL COOLING SYSTEM used in automotive applications. The THERMOSTAT's main purpose is to bring the engine operating temperature to NORMAL OPERATING TEMP as quickly as possible. It does this by REMAINING CLOSED until it's minimum (starts to open) temperature is reached. This contains most of the engine coolant within the engine block and prevents its circulation thru the radiator portion of the cooling system until this temperature is reached. This temperature is usually 195 degrees F on most modern gasoline engines.... this has been determined to be the minimum desired operating temperature for effective emission control purposes. This is also normally the minimum temperature at which the ECM control system goes into "CLOSED-LOOP OPERATION".

Most modern liquid-cooled engines maintain a normal operating temperature in the range of 210-230 degrees F. Once the THERMOSTAT opens, it has LITTLE FUNCTION unless the coolant temperature drops below its rated temperature rating (195^), at which time it will begin to close and raise the temperature of the coolant in the engine block again. During the NORMAL OPERATING TEMPERATURE RANGE the coolant temperature is mainly controlled by the RADIATOR DESIGN, WATER PUMP, TYPE OF COOLANT MIX/RATIO, RADIATOR COOLING FANS and AIR FLOW ACROSS RADIATOR FINS. Ambient air temp and humidity also have an effect in both HEATING and COOLING.

Hope this helps clarify this issue.

But, to get back to the subject of this discussion.... yes, it is possible for synthetic oil to lower engine temperatures. Mainly, this is seen in OIL TEMPERATURE (especially if you have an OIL TEMP GAUGE). I have seen this be as much as 30-40 degrees COOLER difference in racing applications. It has also given WATER TEMPERATURE GAUGE INDICATIONS of 10-20 degrees COOLER at the same time and conditions. Outside ambient air temperature and humidity can CHANGE THIS EFFECT CORRESPONDINGLY.


Sorry, my original post had a few TYPO ERRORS in it. I'm new to this forum and wasn't aware of the 'time limit' on making an 'edit' or 'corrections'. The above "quote" is a CORRECTED COPY.

 

[HTSS_TR]

My experienced was not dino vs syn, but thinner vs thicker syn oils. My '00 E430 was filled with M1 0W40 all its life, until about 9xk miles I changed to PP 5W20 to see if I could reduce engine noise. I went to Vegas last summer on July 04 weekend, the temperature at Death Valley was at normal range above 120F, the coolant temperature was about 3-5F lower than 0W40 the whole trip.
My car does not have oil temperature gauge so I could not say if it is lower with PP 5W20, but coolant temperature is lower for sure.

I am pretty sure on other things, according to trip computer and fill ups, thinner oil improve gas mileage more than 1-2%, in my car the improvement is up to 5-7% with other things such as tire pressure, driving speed, weight carrying ... are similar. Also, engine noise reduced substantial specially at idle. Engine was so quiet with PP 0W20 at idle compares with M1 0W40.

One unusual thing, my car does not consume any oil with M1 0W40 nor with PP 5W20. I expected with much thinner oil I may have to add some between oil change, but I checked oil level once a month, and the level was the same at the time I changed it out as it was first put in.

 

[SlugGunner]

Originally Posted By: BuickGN


I think you meant 195 degrees. The modern cars I've dealt with run right on the thermostat. My TL stays at 194 and has very, very little varience.

My GN stays right on 160 all the time unless I run it hard and then it comes back down to 160 very quickly. I have my fans set to come on at 165 degrees.

On many, the cooling fans dictate at what temp it runs which is what I think you were saying. The thing is, every one that I've seen will heat up to a preset temp, the fans come on, it cools quickly, they shut off, and it starts all over again. Where does a cooler oil temp help this?


I'll say again that the only way cooler oil will affect coolant temps is if the cooling system is marginal already.

I just so happen to have an oil temp guage on the GN and did not see a difference in the short time I ran synthetic. I believe it happens in oil temps but maybe since mine runs a huge cooler already the difference wasn't there.

I'm sure the OP was talking about his water temp, most cars don't come with oil temp guages.


Yes, I did mean 195 degrees.... and you are correct in that an engine with a well designed, maintained, and efficient cooling system will often maintain the engine water temp right at or near the thermostats opening temp. Unfortunately, only the types of people who often frequent these types of forums fall into that category of having WELL-MAINTAINED CARS. Too many of the 'general public' do much more than put gas in them and drive them..... until something goes wrong.

I spent much of my early years in automotive maintenance working in high-performance sports car racing applications. In that field, having an OIL TEMP GAUGE was almost as important as the OIL PRESSURE GAUGE and ENGINE TEMP GAUGE. If you started to see an INCREASE in OIL TEMP, starting to follow with a DECREASE in OIL PRESSURE.... you'd best start planning a 'pit stop' because you were starting to heat up your rod/crank bearings and were either low on oil or about to have 'bearing failure' very shortly.

Normal OIL TEMP for most street engines runs in the 230-260^ range. In sustained high-speed racing applications this can increase to the 280-310^ ranges (depending on running an oil cooler or not). If it starts to run at 340^+, YOU ARE 'IN TROUBLE'.

Considering this difference between normal water temps and oil temps on most modern street engines, your not going to see much change in water temps UNLESS YOU DROP THE OIL TEMP TO AT/NEAR THE WATER TEMP. If it actually got to below the water temp (very unusual, except in COLD WEATHER), it could actually lower the water temp, but never below the thermostat operating temp. With a properly located and efficient oil cooler this is more possible though

In your own application using a 160^ thermostat, you'll never see the oil temp ever get low enough to even come close to ever affecting the water temp.... just TOO MUCH DIFFERENCE in NORMAL OPERATING TEMPERATURES.... especially when compared to most modern auto engines. Keep in mind that most modern automotive engines are designed to operate in the 210-230^F range, with 195^F being considered MINIMUM OPERATING TEMP.

We'll cover the actual ADVANTAGES OF 'LOWER OIL TEMPS' later.

 

[mechtech2]

I don't know why slug gunner states that temp of 295 deg F!
Way too high.
And if a thermostat does not regulate engine temperature, then why does it do so very effectively?

I have seen engine oil temps go down with thinner oil, but not when switching to a synthetic.
But racing or turbos are another world, and extreme heat may get the dino oil out of it's safe/proper operating range. I would always use syth because it can take the heat and won't cook as easily, not to try and cool the engine.

 

[SnakeOil]

Guys, I'm not imparting any new info into this thread. I'm just going to put together a few things that have been said so that some of you will be able to follow the flow of logic.

1. Yes, the thermostat controls the flow of coolant to the engine. However, just because it is doing its job and the "dummy" temperature gauge that 99.9% of you have in your cars doesn't move, doesn't mean that things aren't running cooler if you run synthetic. My temp gauges, move up when you floor it and go down when you coast. The no temp difference is nonsense. Just because you don't have the right tools to see something doesn't mean it isn't happening.

2. The engine coolant doesn't reach the "bottom end" of the engine. This includes the crank, rods, bearings, pistons, rings, and more. That said, having oil that keeps things cool will minimize wear. Metal gets SOFTER when it gets hot. Oil gets THINNER when it gets hot. A synthetic oil resists getting thinner in hotter conditions and will maintain its film strength better while pulling away heat at the same time.

P.S. Thanks for the info SLUG, you said a lot of stuff I didn't feel like typing.

 

[Gary Allan]

Originally Posted By: BuickGN
Oil temps, maybe. Remember that thing called a thermostat?


This assumes that an open thermostat (or one assumed to be modulating) is maintaining its setpoint under normal conditions. My son's Cherokee never sees 195F ..even with a 195F thermostat. That's just the point that it opens. He's lucky to maintain 200F regardless of the ambient. It only alters the duty cycle of the electric auxiliary fan.

Before my coolantil exchanger install, highway speeds at higher ambient temps were 210F. After install, 195F with the air on.

..and yes, with also having to heat the oil under non-stress (and even stressed) output levels, 195F is a struggle in the winter time. This was not as pronounced with heavier oils.


Well ..it's a deep subject.

 

[meep]

Don't say it's true just because we want it to be true... This board used to be self-policing to try to keep to facts and proof.

1. Off Road Magazine did a syn oil/temp study in the late 90's. They instrumented the underhood air temp, crankcase temp, coolant temp, atf pan temp, etc and compared syn to dino. What they found was that syn oil affected BETTER HEAT TRANSFER than dino. Numerical data = good. They provided proof. IIRC they even stated they found no proof that it "reduced friction."

2. Unless somebody can correct me, there is little-to-no actual data suggesting syn oil reduces friction in regular driving. There are many "I believe" and "I think it does" but I've never seen anyone actually provide data. If it did actually reduce friction, *everyone* would see a real mpg improvement with syn and the oems would be all over syn like a fat kid on a cupcake. And by the way, I challenge anyone to find a bottle of oil that does *not* say, "reduces friction..."

3. Syn oil withstands thermal stress better. Even the frying pan test above shows that to a degree (no pun intended). But, the poster's statement that the test proves it keeps the motor cooler is disconnected-- his test shows it can take the heat, does not prove anything else.

4. Thermostats begin to open at a minimal temp and continue to open to full over 15 degrees or so. They don't snap open and snap closed. To that effect, they DO indeed *help* regulate temps, though there is still a good bit of temp swing. Example - radiator cooling is needed for a vehicle cruising at 65 mph. On a 100 degree day it will require more fluid flow than on a 20 degree day because the coolant temp in the radiator will be different, while the amount of heat generated will be similar (excluding air density, etc-BASIC example). air flow over radiator is a variable influence, cooling fan cycling helps regulate be it electrical or thermal/mechanically-reg'ed.

There's a lot of healthy discussion here but have started to turn beliefs into facts more and more. I'd like to get back to keeping them apart until we show it to be actually true.

M

 

[Mark888]

Originally Posted By: meep
Unless somebody can correct me, there is little-to-no actual data suggesting syn oil reduces friction in regular driving.

Do you consider all those tests by Amsoil, Castrol, etc (which are really designed for gear oil and grease) that show they have more wear protection than M1 to be "regular driving." I don't hear many complaints about those tests.

Actually there have been long term studies that show synthetic will reduce engine wear, but those tests are very expensive to conduct and require engine tear down, which few are willing to do.

Friction causes heat, and it is fairly easy to show that engines run cooler (a little) with synthetics. Can you prove that the reason has nothing to do with friction? I don't really know, but am just curious.

 

[440Magnum]

Folks, don't confuse "running at a cooler temperature" with "rejecting less heat."

The controls in the cooling system try to keep the operating temperature fairly constant- whether you're idling in winter or climbing a mountain with a trailer in summer, the coolant temperature (in a healthy cooling system) will vary only slightly.

That's different from the amount of heat energy that is flowing through the cooling system! When you put a heavy load on the engine, the coolant circulates faster (and more of it goes through the radiator and less through the bypass loop) as the thermostat opens, the fans move more air over the radiator (either by an electric fan running more, or by a clutch fan coupling tighter and spinning faster), and a lot more HEAT ENERGY is dumped to the air. But the coolant TEMPERATURE doesn't necessarily change when this happens.

 

[lucerne06]

Not only with a temp gauge, but can you also judge how much cooler an engine is, with the rise and fall of the coolant level in the coolant reserve tank..Like if you monitor it everyday for several weeks, and always every day morning before start up on a cold engine ,the coolant is exactly the same level(cold full),so you have a base to work with, then after running the car for an hour or two, which would give you a very well heated up engine, combined city/highway driving, and the coolant level is lower(did not expand as much) in the reserve tank with synthectic ,then it was with the dino (fluid level was about 1/4 inch higher).Both levels were marked and checked daily and continue to give same reading,,,

 

[meep]

Originally Posted By: Mark888
Originally Posted By: meep
Unless somebody can correct me, there is little-to-no actual data suggesting syn oil reduces friction in regular driving.

Do you consider all those tests by Amsoil, Castrol, etc (which are really designed for gear oil and grease) that show they have more wear protection than M1 to be "regular driving." I don't hear many complaints about those tests.

Actually there have been long term studies that show synthetic will reduce engine wear, but those tests are very expensive to conduct and require engine tear down, which few are willing to do.

Friction causes heat, and it is fairly easy to show that engines run cooler (a little) with synthetics. Can you prove that the reason has nothing to do with friction? I don't really know, but am just curious.


1. wear protection is not synonymous with less friction. In a fluid-dynamic bearing like engines have, metal is not touching metal; it's separated by oil film. Reduced wear comes from high-pressure additives zddp, etc. when the pressure is too high for the film tension. No complaints about those tests-- they just test and prove something else.

2. long term tests proving engine wear... again, let's be careful, while there is certainly a relationship, under normal driving when the high-pressure additives aren't being taxed, surfaces are oil-film separated. AND, what test conditions are present... high mileage, extreme temps, high humidity? those caveats play off of other synthetic strengths that don't relate to friction itself.

3. friction causes heat...: yes, it is documented that some engines run cooler with syn. See my comment above about the instrumented study. syn oil provided better heat exchange.

I am not bashing syn. I use it exclusively. few people see noticeable gains in mpg from syn oils of any consequence. Some do, especially when driving habits keep the engine spending more time below nominal operating temps (short commute, cold climate, etc). If it did provide consistently less friction, everyone would see a diff.

M