A/C effects on MPG....

I am taking my 2001 LS Silverado to the dealer before my warranty expires (3mo/3000mi. GM Certified). I am complaining of poor MPG. Most MPG I got was about 14-15 HWY. He said to fill it up, Apparantly they are going to test the MPG. Then It hit me. I use the AC all the time (south texas 110F+). DO you think they will test without AC and say "Its getting avg MPG"?
Then I wondered from all the previous posts about MPG If you all use your A/C 100% of the time?? I know it obviously lowers MPG but how much?

I am hoping they will reflash the PCM for me. Its a 2001 with 40K on it. It also clatters when I floor it to use passing gear (rarely). It sounds like the timing or something is off a little bit. I use 87 octane..

For the most part the truck runs great, but I want to be sure it is tiptop before warranty expires. I also want all Recall issues addressed (ie tailgate straps etc)

Thanks!!

I am taking my 2001 LS Silverado to the dealer before my warranty expires (3mo/3000mi. GM Certified). I am complaining of poor MPG. Most MPG I got was about 14-15 HWY. He said to fill it up, Apparantly they are going to test the MPG. Then It hit me. I use the AC all the time (south texas 110F+). DO you think they will test without AC and say "Its getting avg MPG"?
Then I wondered from all the previous posts about MPG If you all use your A/C 100% of the time?? I know it obviously lowers MPG but how much?

I am hoping they will reflash the PCM for me. Its a 2001 with 40K on it. It also clatters when I floor it to use passing gear (rarely). It sounds like the timing or something is off a little bit. I use 87 octane..

For the most part the truck runs great, but I want to be sure it is tiptop before warranty expires. I also want all Recall issues addressed (ie tailgate straps etc)

Thanks!!

If you purchased this as a GM Certified Used Vehicle, all the recalls present when the vehicle went through its check out were done (if not, the dealer cannot certify the truck)
As far as gas mileage goes, expect the dealer to check data streams and that is about it.

If you purchased this as a GM Certified Used Vehicle, all the recalls present when the vehicle went through its check out were done (if not, the dealer cannot certify the truck)
As far as gas mileage goes, expect the dealer to check data streams and that is about it.

Ok, It looks like the straps I have are new, there is still apiece of GM paper or tag on them. I thought that was kind of strange. I will just have to wait and see. So does A/C effect MPG very much?? What would you say about that??

I read something about modern A/C being so efficient that the drag of having the windows down hurt your mileage more

I read something about modern A/C being so efficient that the drag of having the windows down hurt your mileage more

That is exactly true.

As far as your dealer finding something causing poor milage, don't hold your breath. I there was something really wrong enough with the truck to cause a milage problem, the engine lamp would probably be on.

14.6 was the best I ever got with my '02 Tahoe 5.3.

Mythbusters did exactly this test. They took two identical ford explorers and took to a circle track. They emptied both trucks tanks and then put exactly 5 gallons of gas in each. One ran the A/C the other ran with the windows down. The one with the windows down ran out of gas.

I am taking my 2001 LS Silverado to the dealer before my warranty expires (3mo/3000mi. GM Certified).

Its a 2001 with 40K on it. It also clatters when I floor it to use passing gear (rarely). It sounds like the timing or something is off a little bit. I use 87 octane..


Greetings Hanibal. While others focused on other parts of your post - I thought I'd focus on this specific piece.

Depending on what speed and RPM you are at when you "floor it" makes a big difference. If you are already at a speed greater than say 40 when you "floor it" - then I'd guess you aren't lugging the engine because you are too low an rpm. So then I'd think - dirty injectors, dirty/plugges fuel filters, poor quality gas, or torque management/transmission issues. I'd focus on the easiest things first - - before considering the more complicated ones.

I have tried running my truck with and without the A/C. Without the the A/C I could gain about 1mpg.

If you are hearing a rattle, you probably need to use an injector or engine cleaner to remove the carbon build up; that will definitly give you better gas mileage.

Ok, It looks like the straps I have are new, there is still apiece of GM paper or tag on them. I thought that was kind of strange. I will just have to wait and see. So does A/C effect MPG very much?? What would you say about that??

The posters are correct, the A/C system doesn't really put that much load on the engine. Most A/C systems use a variable displacement compressor that reduces drag while increasing the efficency of the system.

As far as your knock on hard acceleration is pretty much "normal" it is called flash ping and usually the knock sensors pick this up and adjust the timing.
Some factors that can cause this are carbon buildup in the cylinders and poor quality gasoline (not low octane).
You could ask that they decarbon the engine.
Also use only Top Tier gasoline in your vehicle.
Read more here (http://www.toptiergas.com )

id say if you want better gas mile try not to floor your truck i have a 98 silverado and i constanly get 16 to 16.5 fule injection flush will help using 89oct will likly get rid of your pinging make sure your tires are at good pressures. but mostly try adn keep your foot out of it.

id say if you want better gas mile try not to floor your truck i have a 98 silverado and i constanly get 16 to 16.5 fule injection flush will help using 89oct will likly get rid of your pinging make sure your tires are at good pressures. but mostly try adn keep your foot out of it.

In the 2 months I have had the truck, I used passing gear twice. It is not a habit. I have ran 3-5 tanks driving very cautiously to take a MPG reading. Highway, I use cruise control at 65MPH, and city driving I am like a grandpa (90% of the time :)). I saw that episode of mythbusters and I couldnt remember the result. I will ask them to just do a complete check.

I have emailed the NeslonTune guy but have not yet heard back from him. I am guessing thats my only hope of getting it tuned to my needs. I will know wednesday what the deal is. I am taking the truck to them at 7:30 am.

That is the sweet thing, he tunes every vehicle to make you happy......

Enjoy it, you will see a difference!!

That is the sweet thing, he tunes every vehicle to make you happy......

Enjoy it, you will see a difference!!

If I could just get the guy to reply to my emails :dunno:

The best time to find him is on line at night on LS1TRUCK between 9 and 11 for some reason.... When you get to his place you have to wonder how he does all the work he puts out but the results I've seen on some of the trucks at the track are phenominal... He is in the final planning stage for his new shop.

I understand, patience is the last thing I had spending my money...

I've have 2 vehicles, one a 2001 gm car and one a 2005 chevy truck. Both have the trip computers in them displaying fuel economy, distance remaining on tank, etc. It is super accurate I've found. In both with A/C on, computer calculated fuel economy dropped 0.1mpg. That is negligible.

If I could just get the guy to reply to my emails :dunno:

Just be patient.....I emailed him and it took him almost 2 weeks to get back to me but he did. I'm sure he'll write when he has time.

Since this is about a/c, why does my truck feel like it looses an assload of power when the compressor kicks in? If I'm crusing at 65, I can feel a noticeable difference when it comes on, almost like the engine misses for a second.

I've have 2 vehicles, one a 2001 gm car and one a 2005 chevy truck. Both have the trip computers in them displaying fuel economy, distance remaining on tank, etc. It is super accurate I've found. In both with A/C on, computer calculated fuel economy dropped 0.1mpg. That is negligible.

WHat is your average MPG with the truck?? WHat motor? 4wd?
Thanks for the input. If the dealer says "everything is fine" I am going to drive to San Antonio and get Nelson to fine tune my truck for me.

Since this is about a/c, why does my truck feel like it looses an assload of power when the compressor kicks in? If I'm crusing at 65, I can feel a noticeable difference when it comes on, almost like the engine misses for a second.

Auto A/C is my side job, breadmaker. I would have some gauges put on it. You may be running low on compressor oil. If you have high mileage, it would be a GOOD idea to have the system flushed. Then change the dryer, orifice, oil and freon. The dryer (filter) can get plugged with oil, and the orifice can get plugged with metal shavings under normal wear.
I serviced a 97 GM truck a while back and it was $450 in parts (compressor, dryer, orifice, freon etc) Plus my labor $175 = $625 total!! And that labor price was because it was for a friend. My point: Service your A/C system as you would your engine. A dragging compressor is not a good sign.

EDIT: There is also an throttle compensator switch in the A/C system which adjusts instantaneously for the load the compressor puts on the engine. That may be on its way out (if it is even working).

How much would it usually cost to get it serviced? can't afford alot right now, at least until I get paid next month.

I would have to say that an estimate can be free if you go to a reputable dealer, or shop. If its an idle compensation switch, $75-$150. If a/c needs a flush and recharge, I would say around $250-$300 if its done right. That would have to include new dryer, orifice. Then the system flushed properly then vaccumed pulled on it, then recharge.

I think I'll start with the switch....but I'm sure it could use a good servicing. I've got just over 123K on the ODO.

so then its not true?????.... I like riding with the windows down anyway

I just drove my truck again..I didnt ride in it at all yesterday. Its not so much like the truck missing, but the compressor bogs the engine like hell. When at idle at intersection, the a/c compressor releases it makes the truck jump forward, like its taking alot of power away. The truck idles fine, just feels like it bogs way down when the compressor kicks in.

so then its not true?????.... I like riding with the windows down anyway

I agree kenwood. I thought I was the only one upset to hear that driving with the windows down does more harm than good......i actually don't much care for A/C I much prefer to have "real" ventalation.

I agree kenwood. I thought I was the only one upset to hear that driving with the windows down does more harm than good......i actually don't much care for A/C I much prefer to have "real" ventalation.

why no just open your vents for fresh air and turn the fan off?

why no just open your vents for fresh air and turn the fan off?

I prefer to feel the wind.....at least for a few more days while it's still above freezing outside anyway

on... I meant to say on

on... I meant to say on

I was going to give you some hell about that, but I figured I'd go easy on you lol ;)

I prefer to feel the wind.....at least for a few more days while it's still above freezing outside anyway


I love the feel of the wind :iceslolan

I love the feel of the wind :iceslolan

I do to. But in S.Texas the air temps are 103F+ :smokin: And when humidity is factored in it feels like 115F+. It still almost 100F middle of october.
I enjoy about 1 month of "windows down" weather. Then theres 2 months of cold rainy windows up weather, the rest of the year is A/C weather.

I've got the 4.3 V6/5spd in my '04. I can feel the A/C load the engine down a little in city driving. But I haven't felt a noticable difference at highway speeds, probably due to the engine maintaining a constant speed. I haven't noticed a notable gain or loss of mpg with it on or off in a year and a half of driving it. I try to track every tank, and get 21-23mpg regardless.