what are the benifits of a diesel engine over petrol ?

Answer 1

O.k. Bit long winded this, but thought i'd clear it all up.
I'm an ex army mechanic and all their stuff is diesel for a reason.
A reason they tell us in training.

In spite of lower power to weight ratio and lower maximum rpm, the diesel (or compression ignition engine) compares well with the petrol (or spark ignition) engine. it's thermal efficiency is higher, making it more economical. Heat loss to exhaust is lower and less cooling capacity is required. Increased thermal efficiency means that almost full power is available from cold.

Torque is sustained at lower speeds, giving better pulling power and the need for gear changing is reduced.

The temperature at which diesel fuel gives off flammable gases is much higher than petrol, therefore there is less fire risk and loss from evaporation is less.

Diesel fuel is not cheaper but has a higher calorific value, more useful work is obtained per litre than from the same volume of petrol.

Diesel engines, therfore, have a better fuel economy, and exhaust emmissons are cleaner.

Although the intial cost of fuel injection equipment is high, if properly looked after it is more reliable, and requires less adjustment (manual or automatic electronically) than the ignition equipment fitted to a petrol engine.

To summarise:

Advantages:

Higher thermal efficiency esulting in more miles per gallon.

Low carbon monoxide content (petrol 0.3-4.0% diesel 0.2%)

Almost full power from cold.

Less evaporation of fuel (no fire risk, you can flick matches into diesel and it won't ignite.)

Less water proofing required ( can ford deeper, i.e. off road advantages)

Develops higher torque at lower speeds. (makes car more driveable, less gear changing)

Disadvantages:

Initial cost is higher.

Power to weight ratio is lower

More prone to smoky exhaust (diesel is actually known as "heavy oil". see bottom.

Very efficient fuel filter required.

Goveners required to limit maximum engine speed.

Why Diesel if it's called Heavy Oil?

Diesel is known as diesel because the gentleman who
discovered the principle of Compression ignition engines was called Rudolph Diesel. The first commercial Diesel engine ran on coal dust i believe, but anything which ignites under compression will work. Think custard powder, iron filings, vegetable oil etc.

Glad to be able to answer.

Answer 2

I love reading answers like these when the question is so broad and vague it's meaningless!! I especially like the one where diesel is better for the environment? Why? The first thing you have to consider if you are comparing like vehicles with different engines. Diesel vs Petrol (gasoline for the Yanks!!). If all things are equal, then you look at maintenance and repair, torque, economy - and not in mpg but as a cost per mile due to differences in the costs of fuel. If you need performance, then look at acceleration and hp stats as well as torque. If you are hauling a large boat all the time, torque becomes more important. Then you look at what the engines have on them to get usable numbers. Does it take twin turbos or a supercharger to get the performance gains for the vehicle type for a comparable vehicle with the alternate engine? Those add maintenance issues and possible increased repair costs. The reality is it's about what you feel comfortable with and what makes the most sense for you. Since I know that there are diesel engines in many smaller vehicles in Europe, a Ford Ranger with a diesel is pretty cool. There isn't any one is better than the other, they both have assets and liabilities.

Answer 3

Longevity and durability are probably of even greater significance than the fuel consumption advantage, which is why taxi companies, etc., always choose the diesel version of a particular model. The diesel engined car also gives considerably lower fuel consumption, engine size for engine size, without (in modern diesels*) giving that much away in performance compared with petrol versions. Also, a diesel engine doesn't require the complicated ignition system (and attendant problems) necessary for a petrol engine to operate. It also has enormous torque at low revs which makes it perfect for transport vehicles and trailer towing.

* I believe that Mercedes had to 'detune' the S Class diesel engined models when they found they outperformed the equivalent petrol versions. (Imagine, a diesel doing something like 0-60 in 7 seconds, with a top speed of around 150 MPH... and returning 45/55 MPG!)

Answer 4

depends on if your buying new or not, see the trick is that most car manufacturers charge so much more for the diesel equivilant that it takes at least 3 years to make up the difference of the extra lump you paid ontop of the petrol model (via extra MPG savings). And what do loads of people do when the warranty runs out after 3 years... buy a new car, so they were no better off!! Its a shame people never realise this and think they are saving money thanks to better MPG.

Performance wise-diesel is catching up with petrol but if you look at vw's new TSI engine (petrol,turbo and supercharged) thats now equivilant to the latest 170hp 2.0 VW diesel.

Personally I've got a petrol, I love being able to really get some acceleration out of my motor, right to a high redline every now and then (if required). Diesel-lovers will quote in gear accelleration to the high-hills, but all I have to-do is change down and once again I've got the faster car.

Answer 5

your diesel engine will give you more miles to the gallon,they are far less complicated so should be more reliable, the resale value will be higher ,the engine should last at least twice as long as any petrol providing it is looked after correctly but don't run out of fuel you can't fill it up and go like a petrol.

Answer 6

Lots of touque, good economy.
I drive about 30k/year and run diesel cars, but they are not always cheaper to run.
If you are buying new, the car will cost more.
Fuel is more expensive
On some models, the servicing is more frequent, and therefor more expensive.
All this makes a diesel more expensive for low annual mileage.

Again, if buying new(ish), with an average 10k miles/year, a petrol car will probably be cheaper to run overall

Answer 7

Diesels are more fuel efficient, and so tend to be cheaper to run even though the cost of the fuel is marginally more per litre. They also have less impact on global warming, due to reduced carbon emissions, although the environmental benefits are probably offset by the fact that diesel engines emit more 'particulates', which means they are more smog-causing which is a big problem in cities and urban areas.

Answer 8

A diesel engine develops it's maximum power at much lower revs than a petrol engine, because diesel fuel is an oil, it lubricates the cylinder walls and the engine will last a lot longer
also if it is driven correctly it will return more MPG.
250,000 miles without a major overhaul is not uncommon with a diesel engine !

Answer 9

I had a vauxhall omega diesel that was still going strong at 248000 miles when I sold it.the engine life of a diesel is much longer than a petrol.

Answer 10

Look at this article, it will give you indepth, yet easily understandable information on all you need to know about Diesel engines & the fuel, when compared to Petrol/Gasoline.

Make sure you read all 5 pages of it.