Thread: Petrol V Diesel Ongoing Fuel Running Costs

Originally Posted by powerd

Bacicat
I wonder if that is still the case these days. Diesels used to be low power engines which were derived mostly from trucks, without higher tech approaches such as big/multiple turbos, high pressure injection etc to push the power and torque levels. Diesel rev and perform so much better these days.

Similarly, the durability of petrol engines has increased due to much better oils and fuel injection managing fuel delivery etc. These days, who hears of recent petrol engines having to be rebuilt except where there has been failure such as overheating? For example, my daughter's 2000 auto Astra, at 308,000kms, runs almost like new, with minimal oil use. It has only had a head gasket replaced, a known issue with these. My son's similar car untouched at 200,000kms is equally good. Although I wish I could say the same about the electrics on Astras!

The V8 Ford/Jaguar engine has proven extremely durable, as have the internals of the 2.7 diesel. I am a Jaguar buff and have read more than one article from the UK about the V8s with 200,000 miles on the clock running beautifully, still having spot on compression and no increased oil use.

These days, I suspect most engines regularly maintained will outlast the driver's except perhaps those who do extreme mileages. Wasn't there an Irish Disco3 2.7 that had covered around 500,000 miles (or was that kms?) and was having its engine replaced?

He had a roller rocker failure at (I think) 640K miles. That seems to be a problem on some TDV6 engines. You can hear the hydraulic lifters making a bit of noise at startup if they haven't been fired up for a while.


A well maintained petrol car can last hundreds of thousands of km too - like you said - I have a 2001 Audi A4 1.8t as a daily driver, and you could not pick it has 300K on it. No hardware has been replaced on it at all! Same with my old Pintara TRX - 2 clutch replacements, but other than that all hardware is original at 440K.


Diesels do however have the potential to last longer - less chance of pre-ignition, better chance of having forged internals to cope with the (normally 2x) higher compression - the same reason they also run at lower engine speeds, which also prolongs their life. There's also the matter of the fuel itself - diesel has lubrication properties far in excess of petrol, which is more of a detergent. Instead of assisting in the lubrication of the bore, petrol dilutes the lubrication.


Real world economy of my diesel RRS TDV6 - road tires, no off-road mods:
-40% city, 30% highway, 30% country b-roads - 10.2L/100km
-100% highway - 7.5-8.0L/100km
-100% highway, pulling 2T camper trailer and full vehicle - fridges etc - 11-12L/100km


It's the long trips where the diesel really shines.

Sunny coast to brissie 2 in vehicle .. no traffic delays via airport and Kingsmith to city there and back fill up at each end showed 242 kms and 26 lits of fuel


Av of 10.74 lits /100km.


Round sunny coast no hills 12.4lits/100km average.


Strangely this seems a little higher than when I had the slightly smaller tyre profiles and had a number of trips (exactly the same route and occupants) at avg of 10.5 lits /100kms - marginal - could have been headwind at that small rate.


Anyway bottom line is if you 'boot it' it will change this to an inverted number for sure - 100litres per 10 km lol.


When you consider the ride and the luxury its worth every cent.

Ok these numbers are definitely not something to take to the bank but its a start.

On the way back through Sydney we picked up the D3 after a service and other work that was required.

As I said this is not accurate but it is a start, so using the trip meters in both the D3 and 4 after driving approx 170 kilometres on the freeway South to Goulburn the D3 with 265x70/17" KM2 mud tyres fitted and with a bull bar and winch, second battery, rear wheel carrier, rock sliders etc averaged 10.9 litres per hundred at around the speed limit.

The D4 with 265x50/20' A/T's fitted and all else standard averaged 11.5 kilometres per hundred following behind the D3.

If the D3 had the slightly smaller A/T's fitted it would, from past history, average about 1 to 1.5 litres per hundred better economy.

So after a not to scientific first up comparison there is not that much difference dual wise on the highway. I would however expect a 3.0 litre diesel to have better numbers than the 2.7.

Just towed the 2.5 ton caravan to Canberra with the D3, it averaged 17 litres per hundred driving at 100 kph, at 110 kph it was averaging 19.5 litres per hundred.

Again this is with nearly 32 inch mud tyres on, with smaller A/T's the fuel consumption would be better.

I reckon this is where the V8 D4 will be hard to live with in comparison to the TDV6 D3. But until I get a brake controller fitted to the D4 I won't be able to compare.

Originally Posted by powerd

Bacicat
I wonder if that is still the case these days. Diesels used to be low power engines which were derived mostly from trucks, without higher tech approaches such as big/multiple turbos, high pressure injection etc to push the power and torque levels. Diesel rev and perform so much better these days.

Similarly, the durability of petrol engines has increased due to much better oils and fuel injection managing fuel delivery etc. These days, who hears of recent petrol engines having to be rebuilt except where there has been failure such as overheating? For example, my daughter's 2000 auto Astra, at 308,000kms, runs almost like new, with minimal oil use. It has only had a head gasket replaced, a known issue with these. My son's similar car untouched at 200,000kms is equally good. Although I wish I could say the same about the electrics on Astras!

The V8 Ford/Jaguar engine has proven extremely durable, as have the internals of the 2.7 diesel. I am a Jaguar buff and have read more than one article from the UK about the V8s with 200,000 miles on the clock running beautifully, still having spot on compression and no increased oil use.

These days, I suspect most engines regularly maintained will outlast the driver's except perhaps those who do extreme mileages. Wasn't there an Irish Disco3 2.7 that had covered around 500,000 miles (or was that kms?) and was having its engine replaced?

I know quite a few people that have petrol engined vehicles with well over 350k on them and the engines have never been touched.Everything else fails though,no matter what brand they are,water pumps,radiators,alternators,etc.
One of my brothers has recently done the heads on his D1,just clicked over 360K,first time it has been touched.Had weeping head gaskets,so not a major issue.
People i know with late model diesels seem to get rid of the vehicles before they reach high mileage,mainly because they are company vehicles.

To and from work, semi urban.....11.5L/100 ave

Hwy, home to Glouchester, 10l.3/100 best ever

Towing a 1.5t camper........15l/100 ave

2.7L TDV6, WITH 245/70/17s(30.5") B/Bar, winch, dual batts, drawers, fridge, kaymar rear bar twin carriers, LR tank, roof platform, two awnings, pole carrier.

Best figurs ever was, towing a car trailer(980kg) from Benalla to Myrtleford then with a 2.5t Amarok full of firewood(no idea how much the firewood weighed) from Mytleford to Sheperton, then trailer back to Benalla, 15.4l/100k, about 300ks all up for this, using the trip computer.

The others are recording fuel used and fills, not via the trip computer.

Baz.

You have some significant extra weight (like a 7 seat Sumo full house) and also some real world 'windage' but still shows reasonable Km/Lt results ..

Hate to see the figures if you put 'All' that on a V8.

Horses for courses.

Originally Posted by bacicat

If you plan on keeping the vehicle long term then remember a well maintained Diesel engine will outlive a well maintained petrol engine by quite a bit.

Going back to mechanical injection naturally aspirated diesel versus petrol engines of the 70's sure thing, but a modern petrol v modern turbo diesel that is simply not the case.

cheers