GMC Terrain, Equinox, and SRX Forum banner

1 - 20 of 21 Posts

·
Registered
Joined
·
37 Posts
Discussion Starter #1
Has anyone noticed a trend for your mileage to improve as the temperature increased? I've had my Terrain for 8 months and 24,000 miles and my mileage was low (23 mpg) for months. I changed oil and my mileage didn't increase significantly. But in June when the temperatures starting going up my mileage has gone up to about 28 mpg. I drive 100 miles of highway a day and the air conditioner was running all the time.

I'm just wondering if my engine finally broke in or if temperature has that much of an effect.
 

·
Registered
Joined
·
1,284 Posts
hi ,

wierd , but agree , our mpg was badddddddd , til about 9-10,000miles , then "loosened up" temps ???? break in ??? :cheers:
 

·
Registered
Joined
·
482 Posts
Beyond break in period (What ever mileage that is), My history with vehicles seems to be they are better MPG when temps are in to 50-75 degree range. Warm enough to not be running cold and cool enough to not need A/C a lot.
 

·
Registered
Joined
·
37 Posts
Discussion Starter #4
Terra-Nox said:
Beyond break in period (What ever mileage that is), My history with vehicles seems to be they are better MPG when temps are in to 50-75 degree range. Warm enough to not be running cold and cool enough to not need A/C a lot.
That's been my experience also. But here this summer we've been talking 90+ temperature for the evening ride home.
 

·
Registered
Joined
·
978 Posts
Removing engine break-in from the equation...

There is indeed a direct correlation between MPG and ambient temperature

In some geographic areas the fuel itself must be factored as well...ever hear of "winter gas"?

Without getting into technical reasons which you may or may not want to read about...

Under ordinary circumstances one would expect better milage with warmer temperatures
 

·
Registered
Joined
·
315 Posts
MOCHANOX said:
Under ordinary circumstances one would expect better milage with warmer temperatures
Yep, but alot of that benefit is neglected due to the other factors (ac useage/electrical system charging)....These usually outweight the benefit of denser air
 

·
Registered
Joined
·
978 Posts
grometsc said:
Yep, but alot of that benefit is neglected due to the other factors (ac useage/electrical system charging)....These usually outweight the benefit of denser air
LOL...I had actually typed a similar disclaimer...then backspaced it out thinking I would be getting too technical for the OP...

so thank you for taking care of it for me... :cheers:
 

·
Registered
Joined
·
715 Posts
The last few new cars I've had all 'loosened up' around 20 thousand miles or so.

Mileage improved.

There's 'break in' and then there's 'brake in'.
 

·
Registered
Joined
·
978 Posts
dwendt44 said:
There's 'break in' and then there's 'brake in'.
The latter of which does not apply to engines...
 

·
Registered
Joined
·
315 Posts
MOCHANOX said:
LOL...I had actually typed a similar disclaimer...then backspaced it out thinking I would be getting too technical for the OP...

so thank you for taking care of it for me... :cheers:
:beer:
 

·
Registered
Joined
·
37 Posts
Discussion Starter #11
Nope not too technical. I spent 20 years working for diesel and gas turbine engine manufacturers. I'm not one that really believes in an engine break in period. With modern engines we used to say that once you put fuel to them you were not breaking them in you were wearing them out.

My experience with ambient and engine performance required derates for temperature. Thats why it seemed odd for my mileage to increase so much when I added in the parasitic loads from the a/c.
 

·
Registered
Joined
·
246 Posts
Warmer air is less dense, so you would typically expect less performance in hot months, but better efficiency from a hotter engine. Hotter engines run more efficient. This is why I dont know why GM used a 180 degree Tstat vice a 195F. While driving in the hot weather see if the engine is running a little warmer, normally mine runs on tick before the center one that would be straight down. Wish they had the temps printed on there.
 

·
Registered
Joined
·
315 Posts
2011LT2 said:
Warmer air is less dense, so you would typically expect less performance in hot months, but better efficiency from a hotter engine. Hotter engines run more efficient. This is why I dont know why GM used a 180 degree Tstat vice a 195F. While driving in the hot weather see if the engine is running a little warmer, normally mine runs on tick before the center one that would be straight down. Wish they had the temps printed on there.
actually your logic is backwards on the air....Being the air is less dense when warm, your engine is taking in less air, and thus needs LESS fuel to combust said air. As you mentioned due to the fluids being hotter as well engine/tranny oils, they have less friction on them. The tires are running hotter, and have less roll resistance in summer months compared to winter months.
 

·
Registered
Joined
·
246 Posts
grometsc said:
actually your logic is backwards on the air....Being the air is less dense when warm, your engine is taking in less air, and thus needs LESS fuel to combust said air. As you mentioned due to the fluids being hotter as well engine/tranny oils, they have less friction on them. The tires are running hotter, and have less roll resistance in summer months compared to winter months.
If you need less air and fuel then you just open the throttle body less, so you get less, so it just takes less pedal with denser air. Fuel combusts, and needs the O2/air to do that, so the more work your engine has to do the more you open the throttle, to make air entry easier. All I said though was performance, and I meant better throttle response with denser colder air. Also, less throttle opening means you can maintain higher vacuum levels with the same amount of O2, and all other factors the same can achieve better fuel economy with more dense air.

A big factor though is that the hotter an engine can run the greater efficiency it can achieve. Lets say at 180F the engine makes use of 30% of the available energy in the fuel, but at 210F it may reach 33% efficiency. We limit the temperature to the limits of the materials, and sometimes even lower for long term reliability. Also, the higher the Tstat, the less work the water pump has to do and take energy from the engine to reject heat.

Hotter tires also stick to the road better, so increase resistance, thats why racers will light up their track slicks and may zig zag when behind the pace car. Now because the air expands when hot, the tire pressure can be better maintained to help your rolling resistance. Or use nitrogen to prevent as large of swings in pressure from cold to hot.
 

·
Registered
Joined
·
246 Posts
grometsc said:
Yep, but alot of that benefit is neglected due to the other factors (ac useage/electrical system charging)....These usually outweight the benefit of denser air
And when you wrote this I thought perhaps you were thinking that air was denser when warm, being that AC use in hot weather would negate the benefit of denser air, but the air is less dense when hot.
 

·
Registered
Joined
·
39 Posts
When I lived in Minnesota, there was a huge difference in mileage when the temperature was 0* vs when it was 80*. So yes, IMO all things being equal temperature does affect mileage.
 

·
Registered
Joined
·
978 Posts
grometsc said:
actually your logic is backwards on the air....Being the air is less dense when warm, your engine is taking in less air, and thus needs LESS fuel to combust said air. As you mentioned due to the fluids being hotter as well engine/tranny oils, they have less friction on them. The tires are running hotter, and have less roll resistance in summer months compared to winter months.
X1

Open loop time is also reduced during warmer temps
 

·
Registered
Joined
·
6 Posts
2011 Equinox owner (LT, 4 cyl, FWD) Bought new in July 2011. Kept continous, precise gas mileage record ever since purchase 10 months ago. Very definitely, gas mileage plunged into the teens (16 mpg) for in-town/city driving in the months of December-January with the onset of initial below-freezing weather in Illinois. However, odometer reading was around 4,000 to 5,000 miles - so the engine was still breaking in and when the temps popped back up into the 50 F range, the highway mileage was excellent (into the mid-to-upper 33 to 38 mpg if driven under ideal conditions at continuous 65 mph).
 

·
Registered
Joined
·
10,406 Posts
mike-in-illinois said:
the highway mileage was excellent (into the mid-to-upper 33 to 38 mpg if driven under ideal conditions at continuous 65 mph).
Wow ! You may have one of the most efficient Equinox's in this Forum - congrats !
 

·
Registered
Joined
·
65 Posts
Re: Re: Mileage trend with temperature

It maybe winter gas versus summer gas; less alcohol = better mileage
 
1 - 20 of 21 Posts
Top