Maintaining lightly used car -- idle 10 minutes/week?

[kitatech]

So this means the compressor runs all the time? Or just when the A/C is on? The shop owner told me that I could get the oil circulated during cooler weather by running the defroster, not mess with the A/C.

So, it's either run A/C (with any temp setting), or run the defroster to circulate the oil?

The compressor IS the A/C...
A/C on --->> compressor is on
The defroster is run by the A/C
Defrost ON --->> compressor on
A/C off ---->> compressor off

Either defrost or A/C will circulate oil....

 

[Zenmervolt]

So this means the compressor runs all the time? Or just when the A/C is on?

The compressor runs only when the A/C is on. Some systems cycle the compressor to control refrigerant flow, the system in your car does not, so the compressor will run when the A/C is on and it will do so enough to circulate the oil.

The shop owner told me that I could get the oil circulated during cooler weather by running the defroster, not mess with the A/C.

Most cars run the A/C when the defrost is on because the A/C removes humidity from the air, which helps. So running the defrost setting should also switch on the A/C without you having to manually turn the A/C on.

So, it's either run A/C (with any temp setting), or run the defroster to circulate the oil?

Yes. Just remember that we're talking about the front defroster and not the rear one.

ZV

 

[Muse]

The compressor IS the A/C...
A/C on --->> compressor is on
The defroster is run by the A/C
Defrost ON --->> compressor on
A/C off ---->> compressor off

Either defrost or A/C will circulate oil....

Thanks... one point of confusion for me: If the A/C is Off and the Defrost is On, is the compressor on?

Edit: Evidently the compressor is on when the A/C is off and the defroster on...

 

[Muse]

The compressor runs only when the A/C is on. Some systems cycle the compressor to control refrigerant flow, the system in your car does not, so the compressor will run when the A/C is on and it will do so enough to circulate the oil.



Most cars run the A/C when the defrost is on because the A/C removes humidity from the air, which helps. So running the defrost setting should also switch on the A/C without you having to manually turn the A/C on.



Yes. Just remember that we're talking about the front defroster and not the rear one.

ZV

OK, I get it. Yeah, the rear defroster, that occurred to me the other day. That just runs some current through wires in the rear window I figure.

 

[LTC8K6]

So, just drive your car and don't worry about everything.

Whatever you are worried about, was already thought of and addressed in the design.

 

[kitatech]

Thanks... one point of confusion for me: If the A/C is Off and the Defrost is On, is the compressor on?

Edit: Evidently the compressor is on when the A/C is off and the [FRONT AIR...Kitatech] defroster on...

Done...and done!

 

[WilliamM2]

Thanks... one point of confusion for me: If the A/C is Off and the Defrost is On, is the compressor on?

Edit: Evidently the compressor is on when the A/C is off and the defroster on...

On newer cars the A/C is on in the defrost position. But on my '98 Mazda Protege, the compressor did NOT turn on automatically in the defrost position. I had to hit the A/C button, or the windows would fog up when it was humid.

None of the cars I had previously to that turned it on automatically either.

 

[tortillasoup]

You can even disable the function of turning on the A/C when using the defrost function as that's exactly what I did on my Lexus as I rarely needed the A/C when defogging the windshield.

 

[LTC8K6]

You can even disable the function of turning on the A/C when using the defrost function as that's exactly what I did on my Lexus as I rarely needed the A/C when defogging the windshield.

That's stupid as hell, though...

 

[tortillasoup]

That's stupid as hell, though...

I don't want the A/C running all the time. Sometimes I want to defrog w/o wasting gasoline.

 

[kitatech]

I don't want the A/C running all the time. Sometimes I want to defrog w/o wasting gasoline.

Modern engines waste little gas when running the A/C...Here in all-summer-all-A/C-all year long my MPG consistently exceeds EPA estimates...

 

[LTC8K6]

The A/C system dries out the air, making it way more effective at defogging the windshield.

It's pretty silly, imo, to say you don't want to waste a tiny amount of fuel, but are willing to risk the possible inability to defog your windshield.

Here in NC, you can forget about defogging if your A/C system isn't working. You will be using a towel to defog.

I suppose if you live in a dry climate, you may get away with it much of the time.

 

[tortillasoup]

Modern engines waste little gas when running the A/C...Here in all-summer-all-A/C-all year long my MPG consistently exceeds EPA estimates...

The penalty for running the a/c is quite large actually. On my very well tuned ES350, in neutral, the idle fuel consumption increases from .27GPH to .35GPH using the A/C.

So the A/C penalty is quite high if doing a lot of city driving and less so if cruising on the freeway. But even so, when cruising on the freeway, my fuel economy on the ES350 drops from 38mpg to 33mpg which is within the range of an expected 10-15% drop in fuel economy that's typically attributed to A/C.

Here in NC, you can forget about defogging if your A/C system isn't working. You will be using a towel to defog.

I suppose if you live in a dry climate, you may get away with it much of the time.

You got it! Place I live is pretty dry so I just need a little air to defog the windshield. When its cold and raining outside, so the humidity is high and the windows are fogging up, if I can't defog through the normal means, I'll use the A/C as wiping down the window is a pointless exercise since it'll just fog right back up due to the high humidity.

 

[LTC8K6]

On my very well tuned ES350, in neutral, the idle fuel consumption increases from .27GPH to .35GPH using the A/C.

~10 ounces of fuel per hour. About 13 hours of driving saves you one gallon of fuel.

But you are probably running the A/C anyway to cool the cabin, so cut that number way down.

That's nothing, and it's probably only with the A/C clutch engaged, which is not that often, so it's likely even less. Plus you measured it in Neutral, which is unrealistic.

You are saving such a miniscule amount of fuel to lose good defogging ability.

Makes no sense to me at all.

 

[tortillasoup]

~10 ounces of fuel per hour. About 13 hours of driving saves you one gallon of fuel.

But you are probably running the A/C anyway to cool the cabin, so cut that number way down.

That's nothing, and it's probably only with the A/C clutch engaged, which is not that often, so it's likely even less. Plus you measured it in Neutral, which is unrealistic.

You are saving such a miniscule amount of fuel to lose good defogging ability.

Makes no sense to me at all.

Like I said, I don't have issues with defogging for vast majority of the time which is WHY having the A/C on is pointless. It's a 15% penalty regardless so if you want 15% less fuel economy, go right ahead and use the A/C. I rarely use the A/C to cool the cabin, it would have to be 100F+, stuck in absolutely standstill traffic for me to absolutely require the usage of A/C as the typical humidity at those temps is like 20%.

It's pretty tolerable driving around with the windows down or even cracked with the A/C off. Fuel economy penalty with the windows cracked is less than 1mpg and is definitely less than the A/C penalty even at highway speeds. Now if I had all of the windows down in the car, that would be a different story but it would be so loud that I wouldn't be able to tolerate it.

 

[LTC8K6]

Like I said, I don't have issues with defogging for vast majority of the time which is WHY having the A/C on is pointless. It's a 15% penalty regardless so if you want 15% less fuel economy, go right ahead and use the A/C. I rarely use the A/C to cool the cabin, it would have to be 100F+, stuck in absolutely standstill traffic for me to absolutely require the usage of A/C as the typical humidity at those temps is like 20%.

It's pretty tolerable driving around with the windows down or even cracked with the A/C off. Fuel economy penalty with the windows cracked is less than 1mpg and is definitely less than the A/C penalty even at highway speeds. Now if I had all of the windows down in the car, that would be a different story but it would be so loud that I wouldn't be able to tolerate it.

You still make no sense to me, and your thinking sounds silly, but it's not my car.

 

[tortillasoup]

You still make no sense to me, and your thinking sounds silly, but it's not my car.

Think of it in these terms: I come home and my house is hot, do I turn on the A/C or do I open a window and bring in the fresh, chilled air from the outside? Oh I know, I choose to open a window and bring in the fresh outside air because I don't want to waste energy on the A/C system when there is perfectly decent air outside.

 

[desy]

Yes the drag of AC isn't what it used to be however I think its still an advantage to go without for fuel savings. I also happen to live in a area that defogging isn't so important in fact I'm pissed at my cars that do it automatically I'd rather choose.

 

[LTC8K6]

I leave the house A/C on, I just raise the temp several degrees when I'm not there. That way the house doesn't get too hot, and the humidity stays low, the A/C barely runs, and the A/C doesn't have a big job to do when I come home.

In the summer it's rarely cool and comfortable enough to open the windows, except at night sometimes, or maybe if a thunderstorm front comes around.

For cars, I suspect the load of the compressor bothers small engine economy more than large engine economy. The trend is toward small engines, even in relatively large cars with big cabins to cool.

 

[Muse]

So, just drive your car and don't worry about everything.

Whatever you are worried about, was already thought of and addressed in the design.

Um, there's always user error. That's why driving a car is always dangerous!

Drive defensively!

I know, I'm probably preaching to the choir here...

 

[Muse]

Yes the drag of AC isn't what it used to be however I think its still an advantage to go without for fuel savings. I also happen to live in a area that defogging isn't so important in fact I'm pissed at my cars that do it automatically I'd rather choose.

In my experience the windows only need to be defogged in cooler weather and is accomplished pretty quickly and once the heater has the interior temperature up I can turn it off. So, I'd think that the A/C being on when the defogger is on would be not of great consequence... if you turn it off when no longer needed.

My climate: Almost never gets below freezing, is medium humidity, near the coast (S.F. Bay), typical humidity is over 50% in conditions when I'd need to defog the windows.

For cars, I suspect the load of the compressor bothers small engine economy more than large engine economy. The trend is toward small engines, even in relatively large cars with big cabins to cool.

I read an article the other day, the trend now is to make vehicles lighter, they will be employing all kinds of measures to accomplish that. The average American car weighs 3900 lb., but that will be coming down!

 

[Zenmervolt]

IThe average American car weighs 3900 lb., but that will be coming down!

Interestingly, this is 200 pounds heavier than a 1958 4-door, V8, full-size Chevrolet Bel-Air and approximately the same weight as a 1958 Chevrolet Suburban Carryall (three-rows of seating, the grandfather to today's Chevy Suburban).

ZV