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Diesel Vs Petrol

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September 13, 2009 9:27:04 AM

G'day, anyone out there like to debate the pros and cons of high speed diesel motors vs petrol engines in passenger cars.

I am declaring myself to be a big fan of the high speed diesel, having driven plenty and owned a couple, BUT, that is not too say I do not believe the petrol engine is dead either, particularly withthe chance to run alternate fuels such as ethanol or LNG/LPG/CNG.

Well, over to you fine people, please, kepp it clean, nothing nasty, I am interested in hearing what people have to say on the topic, for or against...

More about : diesel petrol

September 13, 2009 10:14:15 AM

its hard to compare them. diesel engines have more torque n rpm, while also consume less fuel, so are more suited for heavy vehicles and off-road driving. the downside is that they have less horse power and they have that oily smell.
petrol, on the other side, delivers more horse power, so its widely used as a performance fuel in racing, and its the most common, let say, public fuel. downside is that they consume a lot of fuel, and have far less torque n rpm. most petrol engines struggle when faced with heavy loads or off-road tracks.

i personally prefer diesel engines, since their development have brought them so close to petrol engines. I don't see the point of driving on petrol when u get the same performance for less money with a diesel.
September 13, 2009 10:42:56 AM

I'm taking petrol enginge. But it's only because I like more power on high rpms. If you want to have a car which youll be driving in city, then diesel is a better option for you. And it's not true that diesel is cheaper, since you have to pay more for such engine.
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September 13, 2009 10:44:00 AM

I agree, I prefer diesel over petrol, especially since on the roads you don't need the racing performance of a petrol.
September 13, 2009 10:52:43 AM

It depends on the way you drive.
If you want out and out performance then you have to have petrol; LPG, diesel or other fuels (Excluding exotics) do not provide the energy. It does come as a cost though.
For normal driving diesel is just as good, and is better if you need to tow.
JB
Anonymous
September 13, 2009 2:11:43 PM

Diesel during the week (mazda 6 ts2 2.0 tdi) petrol on the weekends (EVO VIII fq300 360 bhp)

Diesel engines are just more efficient and cost far less to run and modern ones are quiet and dont smell anymore!
September 13, 2009 2:37:39 PM

All essetially the reason we bought the Pug, it is a great town car, I am lucky to have access to some fun toys for weekend work, still tingle at the thought of the AMG E-Class, 245km/h before acking off to avoid getting airborne...thrilling.

However, we have a 12 Hour race here every Febrary at Mt Panorama, aka Bathurst, and I am hot on the idea of racing a VW Polo or Golf diesel, not as much outright power, I admit, but plenty of torque for in-gear acceleration, they will certainly climb the mountain no sweat, and actually, produce pretty scary power levels once you start to tune them...decisions, decisions...
September 13, 2009 3:44:26 PM

usually turbo diesel is same like a petrol in performance. it is true that diesel car costs more than the petrol version, but by spending less money on fuel, the investment pays for itself. unless you drive your car 2 times a week, in that case go for petrol. :) 
October 6, 2009 2:11:46 AM

I have owned at least 13 autos, including a Mustang, a Gimmy, a Camero and a Town & Country, a MGB and a Carmengia and a bunch more. Some of them were new, most were used and required all kinds of work which I usually did myself. I love fast and efficient and of all my cars the very best on fuel effeciency and flat out speed is my TDI Jetta 2002.
The Turbo Deisel is kick ass and I can take most stock cars off the line and up the Mountains. I easily can cross 110mph accidently while passing and in regular driving I get 51 mpg. Thats right. 20 mpg better than most of our best milage gass autos get. Consider how many gallons you burn per year and then multiply that by at least 20.
Before Catrina when Desiel was priced fair it cost a third of what Gasoline cost. Now it cost more but still there is no comparison to what I save and get to appreciate in my little speedster.
October 6, 2009 9:44:43 AM

I recently made the change from Petrol to Diesel.... and wont be going back. Sure petrol engines have better throttle response and hence a slight advantge in pulling away from standstill - however the advantge is very small. In my case the turbo diesel in my current car is quicker on the move due to the torque advantages and the light pressure turbo makes up for any performance loss over the old petrol.

Better still - used cars (year old diesels) are just as cheap as petrol - but have better fuel economy
October 6, 2009 10:08:01 AM

Diesel is just downright safer - ask any military unit around the world what fuel they use - it's not because of efficiency, but when there are bullets flying around you don't want to be sitting on a potential fireball. Diesel fuel very rarely ends up catching fire or exploding.

Petrol (gasoline) as we know will catch very easily and IMHO it's not worth even the small risk, especially with my kids in the car. And don't get me started on either LPG or worse, cars with 1/4 ton of lithium under the seats, both of these are mobile mini nukes... Can't be long before we hear a story of a lithium car battery going gaga (like some laptops have done) just with 1000x the amount of explosive lithium!
October 6, 2009 10:36:51 AM

petrol... they dont make a diesel gt500...
October 6, 2009 11:44:09 AM

Diesel.

Modern CRDi engines doesn't have the noise or smell of old diesel engines. And I agree with jamesgoddard's point, diesel needs compression and/or heating up before it burns, unlike petrol which burns instanteneously.

Although most supercars are petrol, that is why the R8 holds a special place in my heart :p .

* Of course, there's the other issues of diesel such as it needs 25% more crude to make and it spews out more particulates than petrol when burned. But I don't mind as diesel cars and fuel is cheaper from where I'm from.
October 6, 2009 11:46:02 AM

The thermal efficiency of the diesel engine is higher that a petrol (gasoline) engine due to its higher compression ratio. After all both are just heat engines are governed by the laws of thermal dynamics. It is about 30 to 40 percent more efficent. You have to weight the fuel costs, versus the difference in price. Diesel engines are heavier, a little noisier and harder to start and usually are more costly. The torque at engine speeds is different. The availiablity of the fuel is another factor. It is usually a matter of personal perference.
October 6, 2009 11:47:32 AM

:D  @ amn
October 6, 2009 11:48:55 AM

Unfortunately the R8 V12 TDi has been canned - too many problems shoehorning the V12 motor into the engine bay and keeping it cool enough.

I went diesel when I last changed cars. I do in excess of 18,000 miles per year and average about 44mpg. I would not buy another petrol car unless my annual mileage drops significantly.
October 7, 2009 10:28:08 PM

mrface said:
petrol... they dont make a diesel gt500...



True Ford might not make a GT500 diesel, but there are some deadset rockets, try VW Touareg R50, 5-litre V10, two turbos, even in a 4WD wagon it will blow a WRX away (Did it myself), and still offer reasonable fuel consumption, plus a full factory warranty.

the point to consider here is that engineers have been working on petrol motors to make them more powerful and more economical for decades.
That research is only just starting on diesels, especially the small capacity 'high speed' diesels, which means in about 10 years time, there will be some genuine purebred race-type diesels on the road...Peugeot uses the same HDi and FAP technology in my road car that is used in its Le Mans winner, except mine is 2.0 litre and the racer is 5.5 litres.
October 7, 2009 10:33:47 PM

448,14,347465 said:
The thermal efficiency of the diesel engine is higher that a petrol (gasoline) engine due to its higher compression ratio. After all both are just heat engines are governed by the laws of thermal dynamics. It is about 30 to 40 percent more efficent. You have to weight the fuel costs, versus the difference in price. Diesel engines are heavier, a little noisier and harder to start and usually are more costly. The torque at engine speeds is different. The availiablity of the fuel is another factor. It is usually a matter of personal preference.


The weight difference is not as great as you think, small capacity diesels such as BMW 2.0-litre, Hyundai 1.6-litre, Mazda's 2.2-litre, plus many more, all use alloy blocks and heads, admittedly with greater torsional rigidity to withstand increased torque, but that is not a bad thing either.

there is a small weight gain around pollution equipment, with particulate filters and so on, but take out the need for distributors and suddenly the difference is back to negligible.

As you say, personal preference is King, i recently tried the VW turbocharged and supercharged petrol motor, what a little rocket, and equally efficient.
roll on the next decade I say, and withit some very interesting cars.
October 8, 2009 12:32:58 AM

gazfast said:
448,14,347465 said:
The thermal efficiency of the diesel engine is higher that a petrol (gasoline) engine due to its higher compression ratio. After all both are just heat engines are governed by the laws of thermal dynamics. It is about 30 to 40 percent more efficent. You have to weight the fuel costs, versus the difference in price. Diesel engines are heavier, a little noisier and harder to start and usually are more costly. The torque at engine speeds is different. The availiablity of the fuel is another factor. It is usually a matter of personal preference.


The weight difference is not as great as you think, small capacity diesels such as BMW 2.0-litre, Hyundai 1.6-litre, Mazda's 2.2-litre, plus many more, all use alloy blocks and heads, admittedly with greater torsional rigidity to withstand increased torque, but that is not a bad thing either.

there is a small weight gain around pollution equipment, with particulate filters and so on, but take out the need for distributors and suddenly the difference is back to negligible.

As you say, personal preference is King, i recently tried the VW turbocharged and supercharged petrol motor, what a little rocket, and equally efficient.
roll on the next decade I say, and withit some very interesting cars.
said:

The higher compression ratio of a diesel engine requires a heavier connecting rods, and the engine block has to be stronger. A turbocharged and supercharged engine increases power by increasing the breathing of the engine and I may be wrong increases the compression ratio of the engine itself. But the turbocharginng and supercharging requires energy from the motor itself.
October 8, 2009 12:50:35 AM

howardp6 said:
The higher compression ratio of a diesel engine requires a heavier connecting rods, and the engine block has to be stronger. A turbocharged and supercharged engine increases power by increasing the breathing of the engine and I may be wrong increases the compression ratio of the engine itself. But the turbocharginng and supercharging requires energy from the motor itself.


Engineers argue that Turbos recapture waste energy from the hot exhaust gases. Recapture waste, as in more efficiency. As in, a 2.0L turbo making the same power as a 3.0L non-turbo but with lower fuel consumption.

Superchargers take power from the crank, they don't reduce waste energy at all, so efficiency goes down.
October 8, 2009 1:02:10 AM

Audi just started advertising the A3 TDI in the States. That might just might end up being my next car...but until then I will continue to enjoy the 40+mpg of my Jetta TDI!

JETTA TDI FTW!!!!!!!!!!!!!!!! :pt1cable:  :o 

America could be on the leading edge of bio-diesel vehicles and bio-diesel technology, especially with the state of the American auto industry and the willingness of Obama to spend my tax dollars to fund alternative fuels and alternative fuel vehicles. Unfortunately diesel technology, and even clean diesel, suffers from a perception issue as many Americans only remember the smelly and noisy diesel cars from the early 1970's as well as the countless 18 wheelers up and down the highways. However, what most Americans and the auto industry fail to realize is that if you truly want a vehicle that will consistently get over 40mpg and still maintain the performance of a V6 or small V8 petrol engine, a 4 cylinder turbo diesel is all you need. And, if the auto industry wanted to sell and the American car buyer wanted a high mileage, fuel efficient vehicle, that is also environmentally friendly, a diesel-electric hybrid vehicle is exactly what they are looking for. Sad to say that, in America, diesel suffers from a total lack of political will, financial backing, and the testicular fortitude required to have clean diesel technology in the forefront of the American auto industry and car buyer.

Yes Americans, you could have your high HP and high MPG cake and eat it too...just start demanding clean diesel cars and light trucks as well as diesel-electric hybrid vehicles!
October 8, 2009 1:26:18 PM

Wait a second now....

Im proud of my carbon footprint!
October 8, 2009 5:30:29 PM

Symbolically Speaking, "Pride's" closest relative is "I Believe" and together they have pissed on more ingenuity and science then any of our other attitudes.

I get the sense that you are just kidding, yet just kidding often is the tip of the ice berg exposing just a hint of a massive belief.
Perhaps not even a belief your committed to personally, but in your sense of humor you have brought the elephant into the room.

The USA is embarrassingly undeveloped in green technology due to such apathy and self gratifying opinions.
Truly Mrface, it is not you I am speaking to, it is the idea you have teasingly rolled across the table and I responsibly must respond to this elephant.
October 8, 2009 6:34:53 PM

lol, wow...

Sure you are free to comment how you want...

Ill keep my gas car for now as I am happy with it, and no it isnt apathy that drives me. I truly love the car. :p 

show me a diesel for the money that gets that power?

some people make sacrifices, albiet for the earth or for the power, its your choice.

[/btw it was sarcasm and you responded correctly. just a litte funny to me thats all]
October 8, 2009 6:50:35 PM

mrface said:
lol, wow...

Sure you are free to comment how you want...

Ill keep my gas car for now as I am happy with it, and no it isnt apathy that drives me. I truly love the car. :p 

show me a diesel for the money that gets that power?

some people make sacrifices, albiet for the earth or for the power, its your choice.

[/btw it was sarcasm and you responded correctly. just a litte funny to me thats all]


I'll keep mine because recycling a fuel-thirsty car to make a less fuel-thirsty car takes more energy than than you could save by driving the more efficient car for ten years!

In other words, its "greener" to extend the life of a "gas guzzler" by ten years than it is to replace it. That's something the politicians and touchy-feely left-coasters won't tell you.
October 8, 2009 7:30:02 PM

yes you are actually correct (as you normally are, ole crashy)
October 13, 2009 12:07:46 AM

I've generally preferred diesel given that with most modern cars it can often be cleaner for the enviroment, more economical in terms of both pricing and mileage while giving a similar amount of power to it's petrol counterpart.

There are many issues which face diesel motorists though. The old stigma that diesel cars are dirty, slow and noisy are slowly becoming debunked only to be replaced with new stigmas (for tightwads and enviromentalists).

Supply, demand and beaurocracy. Kind of sad really when diesel is less refined and theoretically should cost less. I've lived in many countries and see there is a substantial difference in pricing for diesel cars and fuel.

Having said that I'd only buy a diesel from certain makes, VAG, Benz and PSA.
October 15, 2009 11:48:14 AM

diesel is the best out of these two... diesel simply has more chemical energy per liter so in theory you have more miles in your tank... and especially since diesel today is even cheaper then gasoline/petrol, its just a better choise.
In terms of effenciency i dont know how it actually stacks up in energy spent per mile, but id say even if its less efficient at the moment, in the future what will matter is that chemical energy, so when both types of engine have reached near perfect efficiency (chances are will run out of crude long before that) diesel will be better, but also gasoline/petrol will be a bit cheaper because crude usually has more gasoline then diesel, so as there is more gasoline/petrol and diesel will be better, gasoline will always be the choice for our every day lives, and start imagining ferraris and lambos with diesel engines, cause its just a matter of time lol :sol: 
December 1, 2009 11:57:10 PM

For the most part I prefer diesel. They're dependable and can take a lot of abuse. I don't like Canadian and American emission regulations concerning diesel though. A lot of very good engines never make it over here because of that bs. It's good to control emissions but it should be a globally accepted standard not different for every country. Now the issue I do see with that is diesel fuel varies per climate, the colder it gets the lower the wax content. Newer ECM controlled engines make up for that by changing injection duration and timing though.
I like what Crashman stated about the recycling of cars using a large amount of energy. Very few people actually look in to that and nobody looks at the environmental impact of the production of a vehicle. Take any hybrid out there and do a little research about how the batteries are made. I think Top Gear did a thing about this a few seasons back and found that by 200000km the prius does as much pollution as a land rover.
December 7, 2009 6:44:16 AM

I have just changed back to diesel after having a petrol Primera 1.8 for the past 2 years. I'd always had diesel until then and have always loved it. The only downside is that parts are usually more expensive, but diesels are more reliable so this shouldn't be a big problem.
December 7, 2009 8:13:38 AM

Slim Shady said:
I have just changed back to diesel after having a petrol Primera 1.8 for the past 2 years. I'd always had diesel until then and have always loved it. The only downside is that parts are usually more expensive, but diesels are more reliable so this shouldn't be a big problem.


I keep hearing that "more reliable" mantra. Yet I rarely have a encountered internal engine problems. Breakdowns are typically caused by something outside the engine, and that's where diesel and gasoline cars are remarkably similar.

Don't get me wrong, Diesels do get better mileage and wear slower, but today's gasoline cars are typically falling apart before the engine is completely worn out. So from the wear standpoint you end up with what, a better engine in that car that's sitting in a junkyard because...like any other car...it fell apart after 15 years? All four cylinders firing while the gasoline car next to it in the same junkyard burns oil and fires on only three?

What I'm really saying is that of all diesel's advantages, lower engine wear is the one that impresses me least.
December 7, 2009 9:16:00 AM

I don't drive a performance car. I do however drive a Ford Fusion 1.6 Turbo Diesel, because not only is it faster than the petrol version, and it accelerates quicker than the petrol version, but according to the trip computer, I get 63 mpg out of it. Show me a petrol engine that does all of that, and I may be interested. Until then, I'm keeping my diesel.
December 7, 2009 12:59:58 PM

I had a 1991 Golf 2, which used indirect injection and a fixed size turbo charger. Due to its age, exhaust was unfiltered - but it didn't smoke, it didn't smell, and it had terrific fuel economy.
Too bad 1.6L RA VW engines were so unreliable! I'd gladly take a 1.9 over it - with the same turbocharger and intercooler.

Aside from its unreliability (the engine was prone to heat strokes), it is a spitfire - easily leaving similarly sized gas engines in the dust. But, and this is where I'll tell all of you to be careful, while a well made Diesel engine will indeed have more torque at a given RPM than a similarly sized gas engine, it's not always the case.

The most impressive of all small size Diesel engines I've tried were those found on Peugeot 205 turbo Diesel: not only did Peugeot make the most punchy diesel engines of its time, the Peugeot 205 frame (sweet handling, excellent grip, very light) and the turbo on that machine really kick ass.

Too bad it can't be found in the States, moreover it's all manual - for real drivers (I drive sticks myself :p  )
December 7, 2009 6:36:37 PM

mitch074 said:
I had a 1991 Golf 2, which used indirect injection and a fixed size turbo charger. Due to its age, exhaust was unfiltered - but it didn't smoke, it didn't smell, and it had terrific fuel economy.
Too bad 1.6L RA VW engines were so unreliable! I'd gladly take a 1.9 over it - with the same turbocharger and intercooler.

Aside from its unreliability (the engine was prone to heat strokes), it is a spitfire - easily leaving similarly sized gas engines in the dust. But, and this is where I'll tell all of you to be careful, while a well made Diesel engine will indeed have more torque at a given RPM than a similarly sized gas engine, it's not always the case.

The most impressive of all small size Diesel engines I've tried were those found on Peugeot 205 turbo Diesel: not only did Peugeot make the most punchy diesel engines of its time, the Peugeot 205 frame (sweet handling, excellent grip, very light) and the turbo on that machine really kick ass.

Too bad it can't be found in the States, moreover it's all manual - for real drivers (I drive sticks myself :p  )


I used to drive manual transmissions, but that's kind of like the argument over diesel: Automatics hold up to more instantaneous toque, manuals hold up over the long haul. Anyway, it would be tough to drive a HEAVY vehicle from stoplight to stoplight using a manual transmission, and that's mostly what I do now.

Now if I could afford a PLEASURE DRIVING car, I'd be all over the manual option.
December 7, 2009 9:08:21 PM

I switched to diesel to get better fuel economy - however there was some reliability issues too.

Ford 1.6 Zetec used to go through coil packs regularly - they tell me due to poor quality control on the manufacturere of the the coil pack.s

Diesel 1.8 TDCI has no coil pack... no more failures :) 

December 8, 2009 7:33:57 AM

im so jealous...wish we had more diesels here in the US....for some reason, all the luxury brands have them (audi, bmw, mercedes benz...and vw<--not luxury)
December 8, 2009 8:23:08 AM

ahslan said:
im so jealous...wish we had more diesels here in the US....for some reason, all the luxury brands have them (audi, bmw, mercedes benz...and vw<--not luxury)


You should say, all the German brands. You see, fuel is expensive in Europe, and has been for many years. This is the primary reason behind the popularity of Diesel there, and is the reason it almost took-off here in 1979.
December 9, 2009 1:10:29 AM

Hell I want the Isuzu Dmax with the 4JJ engine over here. I've dealt with a good few of the industrial variants of those engines and they are really impressive. I've dealt with a few customers that have 25000+ plus hours on them. Only thing they've done is replaced front seal, rear seal, waterpump, and the egr reed valves. The valves probably would have been fine on one but they ran it under a light load for a long time so there was lot of carbon buildup. Now 25000 hours isn't a long time but by looking at how they are running right now I'd be suprised if they got less than 40000 hours. These engines are also running 24/7 year round in the arctic circle at a gas plant.

I think another reason it's been taking so long for European and Asian diesel to come to North America was because our diesel is crap. We've only just switched to low sulfer diesel in the past few years. The old diesel we used was horrible in the tier 3 and 4 engines. We ran a few tier 3 engines on the old diesel and they smoked like no tomorrow and were very hard to start.
December 9, 2009 1:28:22 AM

Oh and what crashman said about being more reliable. I know of 2 people with more than 750000km on their dodge 1 tons. That is without new mains rolled in. I see industrial engines with 50000+ hours on them without any major work done on them except for seals and oil coolers. My examples are mostly industrial uses but for me the lower engine wear is most important. Dependablity is needed when you're 6 hours away from the closest gas station, in -40C weather, and with no cell phone service. Some of the places I go to you can't even get gas. I do understand what you're saying though because usually something else on the car will break before the engine.
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