Diesel vs. Petrol Cars

[Macquack]

How is the noise output of the new diesel engines?

I have a Daihatsu diesel truck and it sounds like a bag of bolts. I gather the noise comes from the higher compression ratio compared to a petrol engine.

 

[waza1960]

Peugots have had problems with fuel contamination in Australia .For a start our fuel is not the same quality as Europe.Late model diesel car engines' fuel systems run very high pressures and close tolerances making ultra clean fuel essential.Was a story of a Peugot broken down out west ,had to have the injector pump replaced cost $16k just for the pump.

 

[marklar]

How is the noise output of the new diesel engines?

The vee dubs still sound like a bucket of bolts, but at a lower volume than some of the older generations of oilers. If they can make a diesel Eos and people actually buy it, they can't be too bad.

m.

 

[awg]

How is the noise output of the new diesel engines?

I have a Daihatsu diesel truck and it sounds like a bag of bolts. I gather the noise comes from the higher compression ratio compared to a petrol engine.

You pay for what you get, the cheap ones are noisy, the expensive ones are generally quieter, all other things being equal

Peugots have had problems with fuel contamination in Australia .For a start our fuel is not the same quality as Europe.Late model diesel car engines' fuel systems run very high pressures and close tolerances making ultra clean fuel essential.Was a story of a Peugot broken down out west ,had to have the injector pump replaced cost $16k just for the pump.

the diesel injector pumps on the high quality sequential injector systems run at extreme pressure.

they are lubricated by the diesel.

if the fuel is contaminated by water, they are destroyed in seconds.

this is not an uncommon problem, as water infiltrates the service station tanks under various situations, and can also get into the car fuel tank

 

[Happy]

...
if the fuel is contaminated by water, they are destroyed in seconds.

this is not an uncommon problem, as water infiltrates the service station tanks under various situations, and can also get into the car fuel tank

Petrol car can get rid of small amount of water contaminated fuel by adding 100 ml of methylated spirit couple of times a year. But this is hit and miss, as you don't know how much water is there.

 

[awg]

Petrol car can get rid of small amount of water contaminated fuel by adding 100 ml of methylated spirit couple of times a year. But this is hit and miss, as you don't know how much water is there.

this method works well with petrol, however, is not so much of a problem, as the fuel pumps are low pressure, so usually not harmed, also cheap to replace.

wont work with diesel, the HP fuel injector pumps are lubrication critical, and any contaminant will wreck them, cost thousands to rebuild.

I have repaired a few fuel tanks, you would be amazed how much water and rust is in them, cause fuel floats on water, it builds up at the bottom of the tank, and rusts them, water ingress mainly due to condensation

 

[Dowdy]

How is the noise output of the new diesel engines?

I have a Daihatsu diesel truck and it sounds like a bag of bolts. I gather the noise comes from the higher compression ratio compared to a petrol engine.

my engine on my i30 is louder then a cars petrol but it's only noticeable when it's idle

 

[ajjack]

For ordinary city use, best to stay with petrol.
There are not many small dedicated LPG autos available
off the showroom floor.
Diesel? There are some small models avail in the sub 2 liter
size, but they are not cheap.
By the time you factor in the price of diesel fuel and the
prime cost, there is no real saving over comparable petrol models.

Until there is a break thru with hybrids and elec vehicles,
petrol is still the best choice.

 

[matty2.0]

if you're concerned about economy, why not get a hybrid vehicle? there are even electric vehicles for the saavy.

btw ... i thought gav was the "aussiest"

 

[Tysonboss1]

I've never driven an LPG car so can't comment on that. In theory though you'll use significantly more of it than with petrol (and somewhere around twice as much as with diesel) so there's not really that much running cost saving unless you live somewhere with cheap LPG.

By my calculations you would use about 50% more litres of lpg when compared to diesel, So if I increase the price of LPG 50% from 50c to 75c, It's still a massive saving over diesel.

There is a reason why TAXIS run on LPG and not petrol or diesel.

If cost savings is what you want, you can't go past an LPG. When run on LPG my car has similar running costs to a PRIUS.

 

[gav]

if you're concerned about economy, why not get a hybrid vehicle? there are even electric vehicles for the saavy.

btw ... i thought gav was the "aussiest"

Haha wrong forum mate

 

[gav]

It all comes down to you, and what you want in a car.

- Does it matter if the car is rear or front wheel drive, or AWD?
- What type of driving will you be doing?
- How fun is the car to drive? Is performance important to you?
- Does the interior meet your requirements/standards (comfort and looks)?
- Are exterior looks important to you?
- How important is fuel consumption?
- Do your prefer a specific brand or company?
- How important is re-sale value?
- Do you have any specific considerations? (room for kids, golf clubs, will your partner drive the car too, etc)
- And of course, how much can you afford?

For me, there is only one car that ticks all the boxes. I can't afford it yet, but I know the wait will make me enjoy it even more...

 

[awg]

By my calculations you would use about 50% more litres of lpg when compared to diesel, So if I increase the price of LPG 50% from 50c to 75c, It's still a massive saving over diesel.

There is a reason why TAXIS run on LPG and not petrol or diesel.

If cost savings is what you want, you can't go past an LPG. When run on LPG my car has similar running costs to a PRIUS.

LPG is the cleanest fuel.

some things to watch out for.

two different styles of converter

sequential injection is the most modern, efficient and expensive, not all cars can be fitted with it though

older style converters are less efficient, but cheaper to fit

duel fuel conversions, while handy, are the least efficient.

takes ages to fill yr tank with LPG.

I have a notion that LPG, is going to have the excise increased soon

Dedicated LPG is good if you need a big car such as Falcon or Commodore, and do a lot of kms.

I suggest persons do calculations based on how many kms they do, mpg, and time they keep the car, plug in these, and you can work out what is the most economical car for you.

Hybrids are very expensive to purchase, and to my mind, maintenance and resale issues unknown, but questionable

 

[Smurf1976]

By my calculations you would use about 50% more litres of lpg when compared to diesel, So if I increase the price of LPG 50% from 50c to 75c, It's still a massive saving over diesel.

OK, let's take the "base" car, petrol powered, as using 10 litres / 100km for an example.

A diesel version of the same car should use around 7 litres / 100km.

LPG conversion of the petrol engine would use around 14 litres / 100km.

You'll need twice as much LPG as diesel to travel the same distance.

Locally, diesel is 128.9 and LPG is about 67.9 cents per litre. Add in the coming 12.5 cents excise plus GST on that, and LPG increases to roughly 81.65 cents per litre, about 27% more expensive than the volume of diesel required to travel the same distance.

If you have a dedicated LPG engine (which has significantly higher compression than a petrol engine) then you get the best of both worlds. A cheap fuel used with efficiency approaching that of a diesel engine.

Given that LPG is now widely available, it would make some sense to produce dedicated LPG vehicles in my opinion. I assume marketing and consumer acceptance is the reason they're not common.

 

[Tysonboss1]

OK, let's take the "base" car, petrol powered, as using 10 litres / 100km for an example.

A diesel version of the same car should use around 7 litres / 100km.

LPG conversion of the petrol engine would use around 14 litres / 100km.

I think the estimate of an LPG car using 40% for gas than petrol is a bit out. In my experiance it's about 20%.

Plus the LPG price you quoted is way more expensive that it's selling for in sydney. I am paying 49.9c in sydney at the moment. though the more expensive places are about 57.9c (still much cheaper than your quoted price).

where the price of the other fuels is in the range you mentioned.

Both the factors I just listed alter the out come dramatically in favor of LPG.

 

[Mr J]

I cannot agree, how are revs irrelevant if you want to overtake, in a manual car, commencing yr OT manouver at about 3500rpm and finishing at (say)5700rpm, without changing gear?

try that in a diesel

(most diesels redline below 5000rpm vs petrol 6000rpm, and their power and torque curve falls away at high rpm, although they are better at low rpm)

It's irrelevant because revs don't decide how well a car overtakes. What matters is an engine's powerband, and yes the characteristics between diesel and petrol engine's differ, but it is far more complicated than comparing revs. There are some very fast diesels, including race cars.

 

[Kash Kosmo]

I am a retired mechanical engineer by trade & I hold a Motor Mechanics Licence
For Australian conditions Petrol is best followed by Gas or a combo of both

Just to clarify diesel is a fuel oil and is currently more expensive than Petrol in Australia
If not processed and stored properly it can cause problems more so in the more advanced European engines over Japanese engines

When they say in advertisements a diesel car can run 1000 KM on a tank please check the size of that tank & then judge the fuel economy

European cars loose so much value its a travesty
Take it from me I have owned a Lotus, BMW, Merc, Alfa, Citroen and while they were fun to drive they were worth nothing when it came to sell

I now drive Toyota's & Honda's and use E10 fuel

KK

 

[matty2.0]

Haha wrong forum mate

haha ... was wondering if you noticed or would reply!

OP is 'aussiest' i guess.

 

[awg]

It's irrelevant because revs don't decide how well a car overtakes. What matters is an engine's powerband, and yes the characteristics between diesel and petrol engine's differ, but it is far more complicated than comparing revs. There are some very fast diesels, including race cars.

In agreement on most all you say

however I maintain that in the majority of engines, the average torque to power band is spread over wider revs on a petrol than diesel.

ie can maintain useable torque for longer in OT without gear change

ie useable torque diesel 1000rpm to 4000 rpm

petrol 1800 to 5500

not much I know, but still appreciable in OT situation

exceptions for specially developed diesels such as Audi

maybe I am spoiled as I have a V12 Jag, and used to drive an International 345cu 4wd...these motors have massive torque..the Jag has an almost flat torque curve from 1400 to 6000 rpm.

Could be to do with the way I overtake, always try and be near peak torque range at the critical moment

 

[ajjack]

Well said KK and I agree xcept for the E10.

Not only is LPG less economical, but also it produces less power.
Power losses are not so obvious in a large 4 litre motor,
but try LPG in a small 1.6, and its a different story.
Also not all motors are compatible to gas conversion.

Diesels are expensive to buy, and the ADO fuel is also exp.
as compared to petrol, with no regular price discounting.
If you drive less than 15K annually, then the economics of owning
a diesel are not there.