Car decision: diesel or petrol?

[PARANOiA]

I'm in the process of deciding on a first car, and I'm having a bit of a headache trying to weigh up the "right" choices for me, so I'm after a bit of input from the B3D crew. The area in particular I'm looking for advice is on the environmental impacts of choosing a diesel engine vs an unleaded engine.

Now, from the brief bits of information I've read, it looks like a diesel engine seems to more environmentally friendly, due to having lower emissions. When I have talked about this with other people though, they seem surprised - the first image described is smoky and smelly performance.

What sort of measurement should I be looking at when weighing up the environmental consequences of getting a new car? C02 emissions alone?

It should be noted that my choices at the moment are largely between a pricier Polo TDI, and something smaller and cheaper. The TDI caught my eye largely because it's the cheapest diesel on the market.

Thanks for your input, guys. One thing to bear in mind - I know absolutely nothing about cars, engines, or value, so please feel free to give it to me in baby speak.

Cheers

 

[Rainbow Man]

Diesel cars don't smoke these days. They have better fuel injection systems and exhaust filters that deal with that.

The torque of a diesel is also generally much better alos than a gas ("petrol" ) powered engine. And since efficiency is higher it consumes less fuel.

All isn't fun and dance though. While diesels don't smoke they do release more microscopic particles than gas engines and these particles are thought to be very bad for peoples' health with being able to penetrate lung cell walls and wander straight into our bloodstream and all.

Some people also find the engine noise of diesels unsatisfying though most would probably agree such concerns are more or less nonsensical.

So do you choose plague or cholera?

A hybrid car like the Prius is probably a better choice from an environmental point of view if that is your main concern. Plus it draws even less fuel than a diesel.

Peace.

 

[Moffell]

All isn't fun and dance though. While diesels don't smoke they do release more microscopic particles than gas engines and these particles are thought to be very bad for peoples' health with being able to penetrate lung cell walls and wander straight into our bloodstream and all.

A particle filter will see to it that that doesn't happen. Diesel cars shouldn't be sold without them IMO.

As for Priuses, meh, a small TDI polo will most likely match the prius in the city and far surpass it on the highway regarding CO2 emissions. I must say I wonder why there aren't any hybrid diesels on the market yet? The gain might be less but there would still be an increase in fuel efficiency that would be appreciated.

 

[Rainbow Man]

A particle filter will see to it that that doesn't happen.

These particles are too small for these, maybe for any filter. Not even our lungs can filter them since they end up in our blood.

Unfprtunately the better and more efficient the engine the worse the particulate problem it will have. Direct injection increases engine performance and reduces fuel consumption but it also creates more of these very fine particles.

It's the same with DI gas engines too I might add. Running engines on hydrogen would fix it though..

Peace.

 

[_xxx_]

These particles are too small for these, maybe for any filter. Not even our lungs can filter them since they end up in our blood.

No. The modern filters do a great job.

All that aside, I'd go with a good petrol engine, because it responds more lively. While having less max. torque then a diesel, it's just more fun (unless we're talking 250+ hp where it doesn't really matter anymore which one you have).

Diesels consume much less fuel, if money is one of your concerns. Since you're in the US (I think?) the difference shouldn't be huge though.

I only drive a diesel because of the much less consumption, because I drive 40000+ km/year. Otherwise I'd never touch one.

 

[Blazkowicz]

It should be noted that my choices at the moment are largely between a pricier Polo TDI, and something smaller and cheaper. The TDI caught my eye largely because it's the cheapest diesel on the market.

If you're considering a cheap, small car (something well under 1 tonne) a gas engine is still interesting, as fuel consumption/CO2 is close (just because a light car with a small, low power engine is quite efficient), maintenance should be easier/cheaper, and if you're often doing small urban trips diesel isn't great as it hasn't much time to "heat up" (well I feel like a gas car doesn't hate it as much)

a new car that gets my attention for instance is the daihatsu trevis, tiny and cute :smile: .

nothing wrong with the polo TDI if you'll drive often and/or for long.

 

[_xxx_]

nothing wrong with the polo TDI if you'll drive often and/or for long.

With that suspension? No, thanks!

 

[Bouncing Zabaglione Bros.]

No. The modern filters do a great job.

All that aside, I'd go with a good petrol engine, because it responds more lively. While having less max. torque then a diesel, it's just more fun (unless we're talking 250+ hp where it doesn't really matter anymore which one you have).

There have been a new range of diesels that are supposed to feel just like petrol engines to drive. Ford did one a couple of years ago in a Focus, and it's engine characteristics were supposed to be pretty much the same as the petrol version, but with the fuel performance of a diesel.

I was never a fan of diesels, but I had a diesel company car a few years back, and it was actually pretty good. Despite the particulate issue, it actually put out less pollution per mile because the fuel economy was so good (twice that of the petrol equivalent). I had to change my driving style somewhat, but it was great for cruising up and down motorways.

 

[Blazkowicz]

With that suspension? No, thanks!

I'm talking the few I know about engines, I don't know shit about VW suspension.

now what about a citroen C2 or C3 HDi, there's not much wrong with french cars

 

[_xxx_]

It's not just VW, but all those small cars have rather bad suspension. And if you drive much, you learn to hate it very soon

For shorter drives or in the city, I'd actually prefer a small car like Polo.

 

[thana]

hi!

i'm in a very similiar situation - choosing between a diesel and petrol powered used car..
im probably driving something around 10.000 to 12.000 km/year. half of those are short distances (10km to work and 10km back every day), the rest longer distances (100km+).

as i'm really a n00b regarding cars, please excuse my silly questions:

1. lets say the diesel has an fuel-comsumption advantage of 1 l/100km (4.5 vs. 5.5) - would this matter for the short distances at all (because the diesel has to 'warm up' first)? what about the longer distances?

2. how does gas and diesel compare regarding acceleration and top speed, provided they have the same PS and cylinder capacity? diesel is slower, but how much? and what is the general relationship between cylinder capacity and PS - what matters more regarding acceleration?

3. lets say i have a diesel car with 1900cc and 64 PS, and a petrol car with 1400cc and 75 PS - which would accelerate faster? is there some rule of thumb regarding those things?

thx for your patience :smile:

 

[MPI]

Well I'd consider it not worth getting a diesel for just 12000km/year. If diesel fuel was considerably cheaper than gas, as it used(and supposed) to be, then maybe. Here in Sweden there's also a significantly higher road tax on diesel cars older than '05, so here you have to drive like 40-50000km/year+ just to break even...

1. No idea. Best guess; no big difference. Petrol engines are horridly inefficient cold-starters as well...

2. Actually, turbodiesel versions usually do a tiny bit better on the rated 0-100 times than the petrol varieties of the same PS rating. But the difference is miniscule. Horsepower is king.

3. The 75 PS one. There's just too big a difference in PS to make up for different engine characteristics. Besides, with a 64 PS diesel, 'acceleration' isn't exactly the first word that springs into mind.

 

[_xxx_]

1. Warming up has nothing to do with the consumption

2. Diesel accelerates better in lower RPM ranges and petrol just the opposite, so it's dependant on the situation and your driving. Just google for some torque/kW diagrams, there you can directly compare. In the end, the one with more power will win on average

3. many factors involved, there is no rule of thumb there. The engine with more displacement will probably have higher torque and will allow more constant acceleration over a wide rpm range, but the one with more hp will probably accelerate much better within a certain limited rpm range. So it's more about the right tuning. The diesel will probably be run smoother and be more comfortable overall, because the smaller petrol engine will pretty much always need high rpm to get you anywhere.

 

[MPI]

1. Warming up has nothing to do with the consumption.

Surely you jest?

 

[_xxx_]

Surely you jest?

No. I do know the effects, but I was referring to the overall result. He certainly won't be warming it up 27 times a day, so in the overall picture it's negligable.

 

[22psi]

hybrid? toyota

 

[hey69]

i'm driving a bmw320D company car, but if i could choose , i would return to petrol any day.

Turbo diesels are fast the moment the turbocharger (?) starts kickin in , but at very loww speeds, i feel the car is a bit sluggish. I'm used to driving petrol cars..

but then again, diesel consumes much less (6.5l/100km for my current 150hp car) compared to my bmw520i 150hp car petrol engine > 12.5l/100km)
and is overall cheaper.

lots of differences are also depending in the country you live. Do you pay extra tax or not for driving diesel? (in belgium you pay more for the yearly traffic tax, may or may not exist in other countrys)
0.9euro/l = diesel
1.2euro/benzine

 

[RussSchultz]

Right now in the US, diesel is more expensive than premium gas...in my neck of the woods its $2.26/gal for premium and $2.39 for diesel.

 

[Bouncing Zabaglione Bros.]

Right now in the US, diesel is more expensive than premium gas...in my neck of the woods its $2.26/gal for premium and $2.39 for diesel.

But if you're getting twice the miles out of a tank of diesel than of petrol...

In this country, diesel was cheaper for quite a while, with the government promoting it with less tax in order to encourage people to go for the higher fuel economy of diesel. Of course when people started switching and the government started losing tax revenue, the taxes were raised again to claw back some of that fuel efficiency.

 

[Bouncing Zabaglione Bros.]

Turbo diesels are fast the moment the turbocharger (?) starts kickin in , but at very loww speeds, i feel the car is a bit sluggish. I'm used to driving petrol cars..

There's no doubt that unless you have one of the flash "computer controlled to feel like a petrol car" diesels, you do need to change your driving style, think about how you do things as the power characteristics are quite different. I found that diesels were very suited to cruising, thoughtful driving, often having to plan manoeuvres further in advance than a sporty petrol engine.