Hey Camp ... Subi Impreza 2012

[Geoff]

You can have two similar cars with the same mileage but different engines- go to the EPA's website and compare for yourself- http://www.fueleconomy.gov/feg/byMPG.htm

A 34 MPG Passat with a diesel engine produces 0.652 pounds of CO2/mile, while a 33 MPG Elantra with a gas engine produces 0.588 pounds per mile. The 33 MPG gas powered Elantra is better from a CO2 standpoint.

You didn't answer the question.

Take the SAME car. Power it with a diesel engine. Then power it with a gasoline engine. What is the different in MPG?

 

[Geoff]

You can have two similar cars with the same mileage but different engines- go to the EPA's website and compare for yourself- http://www.fueleconomy.gov/feg/byMPG.htm

A 34 MPG Passat with a diesel engine produces 0.652 pounds of CO2/mile, while a 33 MPG Elantra with a gas engine produces 0.588 pounds per mile. The 33 MPG gas powered Elantra is better from a CO2 standpoint.

Also, this is a completely rediculous comparison. An Elantra weighs 2661 pounds. A Passat weighs 3200 pounds.

 

[ctenidae]

You didn't answer the question.

Take the SAME car. Power it with a diesel engine. Then power it with a gasoline engine. What is the different in MPG?

That's not the question I posed. My assertion is that for two cars with similar MPG ratings, the gas engine is a better environmental choice. Period.

To your point, sure, if you have the same car with two different engines (now hold on, I know this may come as a major surprise), they get different MPG ratings. For, say, a 2012 VW Jetta, the diesel shows as 34 MPG, and the gas engine as 27. Not surprisingly, at that spread, the diesel is better. Shocking, I know. However, though there's a 26% difference in MPG, there's only a 9% difference in CO2.

 

[mondeo]

That's not the question I posed. My assertion is that for two cars with similar MPG ratings, the gas engine is a better environmental choice. Period.

To your point, sure, if you have the same car with two different engines (now hold on, I know this may come as a major surprise), they get different MPG ratings. For, say, a 2012 VW Jetta, the diesel shows as 34 MPG, and the gas engine as 27. Not surprisingly, at that spread, the diesel is better. Shocking, I know. However, though there's a 26% difference in MPG, there's only a 9% difference in CO2.

And they don't have the same power or weight. The 2.5L has 30HP up on the diesel and 150lbs down. The 2.0L is old, and not really a good comparison. Heck, it's still a SOHC.

The gas engine is VW's performance engine, the diesel the economy engine. Apples and oranges.

 

[riverc0il]

Cten is correct, diesels by the gallon pollute more than gas. But diesels use less gallons so therefore have less total pollution.

Don't forget that when comparing diesel to gas that the gas EPA estimates for 40 MPG cars are often ceilings or even over estimates and city MPG is dramatically worse. Diesel EPA estimates are often lower than real world and combined is much higher as well. At least this is true for TDI engines. Same car but gas vs diesel is going to be a lot less pollution in comparison than Ctens 9% calculation based on EPA est.

Interesting that both GM and Mazda are going with diesel options. Diesel has the benefit of power over hybrids and comparable gas engines. Seems like a no brainer to offer diesel for folks interested in a combo of both good MPG and performance (and good performance as defined as "good" not great or excellent but certainly better than average or poor in most econoboxes and without sacrificing top fuel performance. That clarification is for mondeo ).

 

[mondeo]

The VW TDI has a compression ratio of 16.5:1. This gives a cycle efficiency of 55%. A gas engine with a compression ratio has a cycle efficiency of 48%, a 14% benefit.

This is the only benefit diesel inherently has over gas. Additional weight for the TDI Jetta is 5% of the total vehicle weight compared to the more powerful 2.5L I5, and 11% compared to the old 2.0L I5, with automatics. The difference is larger with manuals. Just with weight, you've eliminated all but 3% of the benefit. So you get what would be a 40 mpg car and up it to 41.5mpg equivalent. For a $4K increase on base vehicle cost. Anything other difference in efficiency is due to different design philosophy or technology insertion. For the state of the art, gas engines are in a better position with the adoption of direct injection, which took away diesel's remaining advantage in terms of throttling losses. Diesels would need to catch up to variable valve timing to level the playing field.

Most people should go back to having about 1hp/30lb. People tend to get scared when they accelerate at faster than 0.1g, which takes about 50hp at 60mph in a 3000lb car. I have no clue how someone justifys buying a V6 Camry. The power race in plebian cars is absolutely insane. People always say they want decent performance, but they never use it.

 

[riverc0il]

I have no clue how someone justifys buying a V6 Camry. The power race in plebian cars is absolutely insane. People always say they want decent performance, but they never use it.

We can certainly agree on this. The amount of family cars that will never likely get driven barely more than the speed limit with massive high HP engines has boggled my mind for some time.

 

[deadheadskier]

:lol:

you guys are pickin' on me. :lol:

Substitute Sonata for Camery and that's me. I test drove the 4 Cylander and then 6 Cylander when I bought my car. It was a no brainer to get the V6. Do I use that extra horsepower often? Not super often, but definitely everyday. I want my car to have the most usable HP possible for a number reasons.

My 65 year old father and mother are the same way. My mom test drove the Lexus IS 250 with the 206HP engine and then the 350 with the 306 HP engine and it was a no brainer for her to buy the car with the greater HP. My dad test drove his Hyundai Genesis V6 at 333 HP and the V8 at 385 and it was a no brainer for him to buy the V8.

I, and my folks aren't 'performance car' people, but we do want the version of the car we drive to be able to perform at it's maximum stock capability. and be reliable

Question at Mike. You say the gas engine in the VW is the performance engine and the diesel is the Economy. In what way? The greater horsepower and lighter weight gas engine generates far less torque, but pretty much the same acceleratoin numbers as the heavier, lesser horsepower diesel.

Also, if the diesel engine is the Econo engine, then why does the diesel model cost 4 grand more to buy?

 

[mondeo]

Question at Mike. You say the gas engine in the VW is the performance engine and the diesel is the Economy. In what way? The greater horsepower and lighter weight gas engine generates far less torque, but pretty much the same acceleratoin numbers as the heavier, lesser horsepower diesel.

Also, if the diesel engine is the Econo engine, then why does the diesel model cost 4 grand more to buy?

At least it's a Hyundai. I think Toyotas temporarily castrate anyone who gets in the driver's seat. There are 3 cars I dread seeing in front of me entering a highway ramp more than all others: minivans (count 'em all as one, they're all the same,) Outbacks, and Camrys.

I'm not sure what's going on with the acceleration figures, but they can be misleading. For example, the current WRX has a quicker 0-60 time than the STI. Reason being the STI shifts into 3rd at around 55mph, the WRX only has a 5 speed. Fundamentally, when you actually go through the physics, torque doesn't matter in acceleration. It's power that matters. The only reason people talk about torque is that it's an indicator of low-end power. I'd certainly expect there to be more than 0.5s difference to 60, but I really don't pay much attention to VWs because I consider them to be crap in general. Come to think of it, VW's the only compny I know of that hasn't produced an engine held in high regard. Dodge-Hemi, Ford - Coyote/Ecotec/Ecoboost, Chevy - small block V8, Nissan - VQ, BMW - any I6, Subaru - EJ257, Toyota - 2ZZ-GE, etc. VW - nothing.

At the 34mpg vs 27mpg levels, the TDI would pay itself off in about 9 years at 15K/year. Plus it allows VW to market it as a fuel efficient choice, and lure in people that don't do the math and figure out that they'd be better off with the 2L.

 

[riverc0il]

At the 34mpg vs 27mpg levels, the TDI would pay itself off in about 9 years at 15K/year. Plus it allows VW to market it as a fuel efficient choice, and lure in people that don't do the math and figure out that they'd be better off with the 2L.

But the problem with your reasoning is most people get 34 MPG combined at a bare minimum and most do much much better (also the Golf). The only people getting 34 MPG combined with TDI engines are folks driving mostly in cities who would have been better off getting a hybrid for all the stop and go. Those that report driving mostly highways usually have real world combined in the high 30s at least, many report the EPA highway as their actual real world combined. A lot depends on how you drive it but EPA estimates on the TDIs are notoriously lower than real world from my readings online.

 

[Geoff]

Come to think of it, VW's the only compny I know of that hasn't produced an engine held in high regard. Dodge-Hemi, Ford - Coyote/Ecotec/Ecoboost, Chevy - small block V8, Nissan - VQ, BMW - any I6, Subaru - EJ257, Toyota - 2ZZ-GE, etc. VW - nothing.
.

http://paultan.org/2007/05/10/international-engine-of-the-year-2007-results/

I see 2 VW engines on this list from 2007. I have the 2007 2.0L turbo in my car:
1. BMW 3-litre Twin Turbo (335i) 395
2. Volkswagen 1.4-litre FSI (TSI) (VW Golf, Touran, Jetta) 259
3. Porsche 3.6-litre Turbo (911 Turbo) 252
4. BMW 5-litre V10 (M5, M6) 241
5. Volkswagen/Audi 2-litre Turbo FSI 154
6. BMW-PSA 1.6-litre Turbo (Cooper S, Peugeot 207) 135
7. BMW 2.5-litre 6-cylinder (325, 525, Z4, X3) 58
8. Toyota 1-litre 3-cylinder (Aygo, Yaris/Echo/Vitz, Citroen C1, Peugeot 107) 56


Here's Ward's. Lots of VW-Audi engines here:
http://en.wikipedia.org/wiki/Ward's_10_Best_Engines

 

[wa-loaf]

There are 3 cars I dread seeing in front of me entering a highway ramp more than all others: minivans (count 'em all as one, they're all the same,) Outbacks, and Camrys.

Hey, I'm going as fast as I can push my 4cyl! It's that damn minivan in front of me ...

 

[mondeo]

But the problem with your reasoning is most people get 34 MPG combined at a bare minimum and most do much much better (also the Golf). The only people getting 34 MPG combined with TDI engines are folks driving mostly in cities who would have been better off getting a hybrid for all the stop and go. Those that report driving mostly highways usually have real world combined in the high 30s at least, many report the EPA highway as their actual real world combined. A lot depends on how you drive it but EPA estimates on the TDIs are notoriously lower than real world from my readings online.

The 2.5L gets better than EPA estimates, too. And those drivers aren't trying as hard to get good mileage like those that get a diesel are. The EPA estimates for any car where someone is reporting mileage are lower than actually achieved, because the people actually tracking mileage are the ones driving in such a way that they overachieve.

 

[Geoff]

The 2.5L gets better than EPA estimates, too. And those drivers aren't trying as hard to get good mileage like those that get a diesel are. The EPA estimates for any car where someone is reporting mileage are lower than actually achieved, because the people actually tracking mileage are the ones driving in such a way that they overachieve.

There's a lot to this. People who buy diesels and hybrids are far more likely to be hypermilers.

I saw 21 mpg out of my V8 SUV on a KMart trip last fall. My tire pressure gauge was screwed up and I'd overinflated the tires by accident. The air temp was about 50F which is probably about optimal for the mix of wind resistance and engine performance. I had the cruise control set at the speed limit the whole way and didn't hit any traffic. My more typical mileage is 17 mpg and 16 mpg when it's subzero.

I usually do my part by running red lights and stop signs.

 

[riverc0il]

The EPA estimates for any car where someone is reporting mileage are lower than actually achieved,

Not true. While researching the Elantra, I found the overwhelming majority of drivers were not getting 40 MPG highway (by significant variances). Online publications (independent resources that removes the self selection issues regarding MPG reporting online) that beat highway EPA on TDI models reported getting less than EPA on the Elantra. This is just one example, I am sure there are many others.

 

[mondeo]

Not true. While researching the Elantra, I found the overwhelming majority of drivers were not getting 40 MPG highway (by significant variances). Online publications (independent resources that removes the self selection issues regarding MPG reporting online) that beat highway EPA on TDI models reported getting less than EPA on the Elantra. This is just one example, I am sure there are many others.

True. Because Mustangs and Corvettes are the opposite, often higher than EPA. So my two anecdotes beat your one anecdote.

The EPA has a set means for testing mileage. Variance from EPA is solely due to driving style and specific use case.

 

[riverc0il]

True. Because Mustangs and Corvettes are the opposite, often higher than EPA. So my two anecdotes beat your one anecdote.

The EPA has a set means for testing mileage. Variance from EPA is solely due to driving style and specific use case.

You are a piss ant, lol. You proposed an absolute truth. I did not rebut by proposing an opposing opposite absolute truth but merely only evidence that your absolute position was false.

EPA tests are conducted by the manufacturers with very small percentages verified officially (less than 10% as I understand). Perhaps the methodology is standardized but it is hard to believe it is a perfect system. Variances both significantly above and below EPA estimates are reported on a wide range of cars.

What the F? It needs to snow.

 

[mondeo]

You are a piss ant, lol. You proposed an absolute truth. I did not rebut by proposing an opposing opposite absolute truth but merely only evidence that your absolute position was false.

EPA tests are conducted by the manufacturers with very small percentages verified officially (less than 10% as I understand). Perhaps the methodology is standardized but it is hard to believe it is a perfect system. Variances both significantly above and below EPA estimates are reported on a wide range of cars.

What the F? It needs to snow.

Sorry, forgot what I'd written. But the Elantra seems to be the exception, not the rule. Even STIs, 'Vettes, Mustangs, etc. seem to get better than EPA mileage when it's reported by owners, and they'll typically get driven harder than the EPA guidlines. I know that, except for the phases where I just drove the thing hard, my old Cougar got upper 20s combined and 33 when it was in heavy highway driving mode, significantly better than EPA estimates which would now be lower. My STI, when I've paid attention to it, gets around the EPA estimate, and I drive it hard.

 

[Geoff]

Sorry, forgot what I'd written. But the Elantra seems to be the exception, not the rule. Even STIs, 'Vettes, Mustangs, etc. seem to get better than EPA mileage when it's reported by owners, and they'll typically get driven harder than the EPA guidlines. I know that, except for the phases where I just drove the thing hard, my old Cougar got upper 20s combined and 33 when it was in heavy highway driving mode, significantly better than EPA estimates which would now be lower. My STI, when I've paid attention to it, gets around the EPA estimate, and I drive it hard.

The revised EPA numbers take into account things like driving in cold temperatures, the fact that just about all drivers exceed the speed limit, and rapid accelleration. For most cars, if you're driving the speed limit in warm temperatures and take it easy with the throttle, you're going to beat the EPA estimate.

I'll bet that few cars going skiing when it's -10F see anything like the EPA number. It's cold. You're speeding. You're probably driving aggressively. You have extra weight in the car.

 

[AdironRider]

The revised EPA numbers take into account things like driving in cold temperatures, the fact that just about all drivers exceed the speed limit, and rapid accelleration. For most cars, if you're driving the speed limit in warm temperatures and take it easy with the throttle, you're going to beat the EPA estimate.

I'll bet that few cars going skiing when it's -10F see anything like the EPA number. It's cold. You're speeding. You're probably driving aggressively. You have extra weight in the car.

I get exactly in the middle of my city and highway ratings in my Nissan Frontier in the winter time here in Wyoming when it averages 5 degrees for our average low temps. I get right at 18 with daily use of 4x4. Summer time it ups to 22-24 which is substantially over the ratings of 15/19 respectively. These are my combined figures averaged out over 40+k miles that Ive driven the truck so far. Lifetime average is 21.1, and keep in mind the average low even in July in August out here is barely above 40 degrees, so Im pretty much commuting to work every day in the sumemr time in your average temps for the entire winter. Worse in the winter. Higher elevation though so the wind resistance is less.

I will admit the natural driving tendencies of most of the population out here is to drive the speed limit so that helps, but I wouldnt say that most people are getting below their combined figure even in the winter time, especially back east where most driving to ski areas is highway or county highway (45-55mph speed limits).

If anything its that damn ethanol gas. My mpg drops by at least 1 mpg, more like 2 or 3 when I fill up with that crap. Luckily the local gas station is still one of the few holdouts nationwide that doesnt put any ethanol in their fuel. So that helps my milage as well.