I had spark plugs replaced, fuel economy went down???
12-23-09, 09:54 PM
#1
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Thread Starter
I had spark plugs replaced, fuel economy went down???
On Monday, I had my spark plugs replaced and ATF drained and filled by Toyota. I haven't done any highway driving since, but my fuel economy after a fill up this morning and a few trips around town is sitting at over 14 l/100km and seems to keep increasing (higher is worse...). Before the change, around town I would probably be getting around 12 max. The listed "city" fuel economy for the car is around 11 l/100km.
I haven't noticed anything else odd about the behavior of the car. Is it just my mind playing tricks on me? I don't think I've ever noticed it get this bad before. I'm wondering if I should be taking the car back and complaining that they botched something up, but given that the car seems to be performing fine maybe I'm just overreacting - I can't think of any reason changing the plugs should do this unless it's some kind of ECU self readjusting thing and I need to give it a few tanks of gas to sort itself out.
Any ideas?
P.S. The plugs I had them replace with were the OEM Denso parts that I had previously ordered from Sewell.
I haven't noticed anything else odd about the behavior of the car. Is it just my mind playing tricks on me? I don't think I've ever noticed it get this bad before. I'm wondering if I should be taking the car back and complaining that they botched something up, but given that the car seems to be performing fine maybe I'm just overreacting - I can't think of any reason changing the plugs should do this unless it's some kind of ECU self readjusting thing and I need to give it a few tanks of gas to sort itself out.
Any ideas?
P.S. The plugs I had them replace with were the OEM Denso parts that I had previously ordered from Sewell.
12-24-09, 07:34 AM
#3
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Thread Starter
The Canadian service schedule for the GS states that you have to replace the ATF every 96,000km... I did mine a bit early, just because... at any rate, it has to be done here to protect your warranty.
12-24-09, 07:40 AM
#4
Is it possible the change in the fuel for winter could be the cause. I know in my area my mileage goes down when they make the switch and when we go back to summer gas it improves. Could just be the timing of the two and colder weather?
Other then this I dont see what would have made the change.
Other then this I dont see what would have made the change.
12-24-09, 09:01 AM
#5
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Does fuel quality have anything to with fuel economy? Ie, fuel with great sulfur content... since our fuel is 95 RON. Never seem to get anything better than 20L/100km
12-24-09, 09:46 AM
#7
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Thread Starter
Denso, Part #90919-01249
Bought from Sewell, they confirmed at the time of my order that they are the correct part. I also trust (maybe wrongly!) that Toyota would have alerted me if the plugs were incorrect before they installed them.
As for the fuel, I filled up at the same station that I always fill up at... I use Shell V-Power almost exclusively (Shell happens to be the most convenient station to me, and I get 3c/L discount using my credit card there so it's kind of a no brainer.
http://www.shell.us/home/content/usa.../about_vpower/
Bought from Sewell, they confirmed at the time of my order that they are the correct part. I also trust (maybe wrongly!) that Toyota would have alerted me if the plugs were incorrect before they installed them.
As for the fuel, I filled up at the same station that I always fill up at... I use Shell V-Power almost exclusively (Shell happens to be the most convenient station to me, and I get 3c/L discount using my credit card there so it's kind of a no brainer.
http://www.shell.us/home/content/usa.../about_vpower/
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12-24-09, 11:54 AM
#8
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I get about 18 L/100km (100% city) with any premium fuel (used Shell V-power for a while, and that didn't help). Change is about +/- 1-2 L/100km from winter to summer. I'll trade you for 14 any day on a GS 350.
12-24-09, 12:01 PM
#9
Lexus Fanatic
remember that low temps and high ambient temp actually decrease the fuel efficency. Also trying to do little peels and drifts in the snow will do it
12-24-09, 12:03 PM
#10
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Thread Starter
Really, that sounds terrible. On a 40 minute highway trip immediately after fill up (before spark plug change, at any rate), I ended my trip at 8 l/100 km.
Last edited by BinaryJay; 12-24-09 at 12:09 PM.
12-24-09, 12:09 PM
#11
Lexus Fanatic
As if we really needed another reason to hate winter.
Those of you living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).
Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.
How much worse?
Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:
MPH-----AMBIENT-TEMP-----MPG (US)
60------------95----------52.98
60------------85----------52.62
60------------75----------51.16
60------------65----------49.12
60------------55----------47.22
60------------45----------44.67
60------------35----------43.05
60------------25----------41.54
60------------15----------39.41
60------------05----------38.09
Look at the extremes: the coldest MPG is 28% lower than the warmest.
My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse.
Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...
9 reasons your winter fuel economy bites
1. More idling
This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.
Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).
2. Low tire pressure
Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).
3. Increased rolling resistance
Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).
4. Crappy road conditions
It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)
5. Lower average engine temperature
In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.
A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).
Also related...
6. Higher average lubricant viscosity
Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.
Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.
7. Weaker gasoline
Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)
8. Higher electrical loads
In colder temps, you use electrical accessories more often:
- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)
9. More aerodynamic drag
No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).
A vehicles aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% .
Sorry to get so technical but this is whats really going on most likely
Those of you living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).
Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.
How much worse?
Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:
MPH-----AMBIENT-TEMP-----MPG (US)
60------------95----------52.98
60------------85----------52.62
60------------75----------51.16
60------------65----------49.12
60------------55----------47.22
60------------45----------44.67
60------------35----------43.05
60------------25----------41.54
60------------15----------39.41
60------------05----------38.09
Look at the extremes: the coldest MPG is 28% lower than the warmest.
My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse.
Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...
9 reasons your winter fuel economy bites
1. More idling
This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.
Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).
2. Low tire pressure
Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).
3. Increased rolling resistance
Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).
4. Crappy road conditions
It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)
5. Lower average engine temperature
In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.
A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).
Also related...
6. Higher average lubricant viscosity
Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.
Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.
7. Weaker gasoline
Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)
8. Higher electrical loads
In colder temps, you use electrical accessories more often:
- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)
9. More aerodynamic drag
No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).
A vehicles aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% .
Sorry to get so technical but this is whats really going on most likely
Last edited by I8ABMR; 12-24-09 at 12:12 PM.
12-24-09, 12:12 PM
#12
Moderator
Thread Starter
Now probably what happens, as mentioned is that at some point the fuel suppliers change over to a winter blend that gets you less bang for your buck... I suppose it's totally possible that it was a coincidence that my fill up after the plug change happened after my station switched blends. I don't drive a lot at all (I work out of a home office) so it had been a couple of weeks since I last put gas in the car.
12-24-09, 12:20 PM
#13
Lexus Fanatic
As if we really needed another reason to hate winter.
Those of you living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).
Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.
How much worse?
Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:
MPH-----AMBIENT-TEMP-----MPG (US)
60------------95----------52.98
60------------85----------52.62
60------------75----------51.16
60------------65----------49.12
60------------55----------47.22
60------------45----------44.67
60------------35----------43.05
60------------25----------41.54
60------------15----------39.41
60------------05----------38.09
Look at the extremes: the coldest MPG is 28% lower than the warmest.
My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse.
Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...
9 reasons your winter fuel economy bites
1. More idling
This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.
Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).
2. Low tire pressure
Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).
3. Increased rolling resistance
Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).
4. Crappy road conditions
It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)
5. Lower average engine temperature
In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.
A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).
Also related...
6. Higher average lubricant viscosity
Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.
Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.
7. Weaker gasoline
Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)
8. Higher electrical loads
In colder temps, you use electrical accessories more often:
- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)
9. More aerodynamic drag
No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).
A vehicles aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% .
Sorry to get so technical but this is whats really going on most likely
Those of you living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).
Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.
How much worse?
Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:
MPH-----AMBIENT-TEMP-----MPG (US)
60------------95----------52.98
60------------85----------52.62
60------------75----------51.16
60------------65----------49.12
60------------55----------47.22
60------------45----------44.67
60------------35----------43.05
60------------25----------41.54
60------------15----------39.41
60------------05----------38.09
Look at the extremes: the coldest MPG is 28% lower than the warmest.
My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse.
Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...
9 reasons your winter fuel economy bites
1. More idling
This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.
Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).
2. Low tire pressure
Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).
3. Increased rolling resistance
Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).
4. Crappy road conditions
It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)
5. Lower average engine temperature
In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.
A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).
Also related...
6. Higher average lubricant viscosity
Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.
Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.
7. Weaker gasoline
Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)
8. Higher electrical loads
In colder temps, you use electrical accessories more often:
- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)
9. More aerodynamic drag
No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).
A vehicles aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% .
Sorry to get so technical but this is whats really going on most likely
please read all of the info. Its goes much further than "poor winter gas quality". When the air is more dense and the ambient temps are very low then the ECU will need to dump more fuel to maintain the same air /fuel ratio + the other 8 points listed. Its all physics. I am surprised you guys living in these cold temps are not aware of this stuff. Look it up. Its 100% correct I dont know how much technical anyone can get in trying to answer the question posted.......maybe to technical. None the less its all 100% correct
Last edited by I8ABMR; 12-24-09 at 12:41 PM.
12-24-09, 01:01 PM
#14
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I also have a Mitsubishi Outlander, which gets better mileage than rated (12.3 rated, but get around 11.2)...so its not me pressing on the gas harder or whatnot.
Try disconnecting the battery and see if that fixes anything. The ECU may need to re-learn how to use the new spark plugs properly. I would say it sounds more like a combination of different fuel mixtures, changes in temperatures,etc all coming together to decrease performance.