Petrol or diesel?

[markjay]

Problem with that theory is manufacturers are going for smaller capacity 4 cylinder turbo charged petrol engines, which make a racket when pushed. Most days, I'd rather drive my C250d Estate than my SLC300 bacause it's more refined inside & has 500NM of torque making each journey a pleasure. The petrol engined SLC just feels like hard work.

My 1.6L Turbo CGI M274 certainly does not make a racket when pushed, but I have not yet driven the 1.5L Turbo EQ Boost M264.

 

[C250BLUE]

My previous two cars were diesels, no issues at all apart from a bit clanky on cold mornings. I bought another diesel c220d which hopefully should be getting delivered on Thursday. Hopefully Mercedes have fined tuned the engines on the new 'C class.

 

[markjay]

I guess it differs from one car to the other.

I have a Kia Soul II 1.6L CRDi Diesel, and a W204 C180 1.6L petrol.

I drove each car to France and back. The Kia was much more frugal (it will go from London to Paris and back on a single tank), and the tall driving position is fantastic, but the engine noise in the cabin causes fatigue. The petrol W204 was much quieter resulting in a much more relaxing drive.

As I said, the only Diesel car I have personally driven and was as quiet and refined as a petrol car, was an S350 CDI which I drove from Salzburg to Munich a few years back.

 

[Crazyfool]

Problem with that theory is manufacturers are going for smaller capacity 4 cylinder turbo charged petrol engines, which make a racket when pushed. Most days, I'd rather drive my C250d Estate than my SLC300 bacause it's more refined inside & has 500NM of torque making each journey a pleasure. The petrol engined SLC just feels like hard work.

Yeah I think that’s where it’s different for me. The E350 just pulls, even when fully laden and it’s extra large tank enables me to get just over 100 miles per quarter of tank.

The E400 feels more relaxing and refined, yet when you put your foot down, boy does it go! It however doesn’t have the extra large tank, so I’m watching the needle move quicker. Doesn’t bother me though because the 350 is our workhorse, the 400 is a fun car which won’t be doing any more than 10,000 miles a year.

 

[Alex225]

Diesels are as clattery as they have always been, its just that manufacturers have improved the interior sound insulation so occupants don't notice the clatter as much.

I might argue that point a little bit. Only as I have an E320 with the old 3.2 inline six, I'm a huge fan of the engine and from within the car you don't really hear it much. From the outside, typical agricultural diesel sound. What I'd expect of a 16 year old diesel.

By contrast my other half has a CLS350 from 2009 so the newer 3.0 V6 diesel. From outside of the car it is a hell of a lot quieter and smoother than my E. Inside isn't dissimilar although oddly when you give it some harder acceleration it sounds surprisingly good. I would imagine some of the larger diesels found in even more modern Merc/BMW/Audis are further refined. Perhaps not so much if you're looking at sub 2.0 four cylinder diesels though.

As for buying diesels now, I still would but then it suits my driving. Only 12-13k a year but that is all motorway driving, I can get 45-50mpg, alongside tonnes of torque and decent refinement. If I was replacing my E I'd buy another diesel for the same purpose but then I'm looking at cars which are 7+ years old and lost 80% of their value so I'm not phased about resale so much.

 

[BTB 500]

We've had a lot of trouble with the 3.0 CDI OM642 in our Vito over the last year, from about 90k miles onward. 8 instances of EML and/or limp mode, off the road for maybe 6 weeks overall, and a total bill almost £6000 (amongst other things it required a new turbo and new manifolds - an engine out job). Had a few breakdowns before that as well - failed CPS and DPF pressure sensor, and (annoyance only) 5 or 6 failed glowplugs (needs another one doing at the moment). Maybe we've been unlucky but modern diesels are just too complex for their own good IMHO and I wouldn't buy one again if I had the choice. Never mind the image problem they have now, which I think is quite likely to affect future resale value.

 

[ph47mf]

Well I'm in the car delivery business and what the drivers drive next is always like a little surprise to them and whenever they see a petrol car they become disappointed simply because it doesn't perform quite as well on the motorway or the A-roads, and they will most likely have to stop more for fuel.

We have driven thousands of diesels and only a few give us problems, mostly older Jags/Land Rovers, warning lights are almost always on and when they're not in the mood, they just stop and this usually happens on the motorway

 

[Deleted member 6183]

We have no more diesel in our household.

I was the last to drive diesel and it went last year following turbo failure. To be fair the car had only cost me £80 in repairs over the previous 6 years, I bought it just as the warranty ran out.

I was talking to a relative 2 weeks ago who had bought a new diesel SUV, he does live in the **** end of nowhere, and felt that he had been a bit of a mug given the current sentiment around diesel.

I doubt many of us really wanted diesel in the first place, I recall it was only weirdos who bought into them in the 80s and they were pretty dreadful, it's with relief that I know I'll no longer need to run diesel as more petrol and/or hybrid options are becoming available.

 

[MikeInWimbledon]

I'd looked for an E500 estate for six months and couldn't find one. Lobbying from diesel BMW enthusiasts resulted in me buying a 535d SE touring.
Which is a lovely car but.... I've decided to get rid of it after 8,000 miles (including a 3,000 mile trip round France this Winter).
The 535d SE is a lovely car: Powerful, especially in the mid range, good looking (LCI version: less "Edna"), a good size, and a smooth ride on normal tyres and SE suspension (avoid M Sport & run flats)

But, I really don't like the turbo diesel thing. I much prefer the smooth, endless acceleration of petrol.

As for the "Tractor" allegation: I don't see that as an issue. Might be true for small diesels, but the noise of the 3.0 litre diesel is not at all intrusive.

The "Economy" argument is a fallacy. Diesel is more expensive, and there's no question that diesel engines cost more to maintain, beyond the first five years. (I personally haven't had any problems at all - but others can provide plenty of evidence)

Fuel economy is usually a bit of a red herring. When someone tells me they're spending £5k a year to finance a new big family hatchback, I get the vapours. Ownership cost is about depreciation, finance, tax and fuel.

So I'm back in a superb, immaculate, as new E350 petrol "for family duties." But if anyone has an E500 Estate.....

 

[TeddyRuxpin]

I love my E350 CDI - the torque and economy (52MPG on my last long run vs a max 33mpg in my old 2.5L BMW - a big enough difference to cover the extra expense of the fuel) are fantastic, and I want that low down torque and not have to rev the balls off it or drop into second at 50mph to get any power.

I do miss the BMW inline 6 that I could barely tell was running when at a standstill, though. My car (231BHP) does feel a bit more tractor-y than the new diesels, I think, at least when cold.

I plan to keep it for a few years, until I can get a hybrid that offers me the same/better grunt and even better economy.

Then maybe electric after that....

If I lived more centrally though, I'd never have a diesel for all those short trips. But I probably wouldn't have a huge E-Class either!

 

[Deletedmember130310]

Compare the warranty costs on a petrol and diesel model of equivalence - the difference in costs will tell you which will be more expensive to repair

 

[John]

Compare the warranty costs on a petrol and diesel model of equivalence - the difference in costs will tell you which will be more expensive to repair

Can you extrapolate purely the cost of engine faults and repairs from them i.e. are they categorised like that?

 

[Bellow]

In the original cost, ie the build cost of the engine - the diesel engine's fuelling equipment accounts for one third of total cost. That is massive compared to petrol and while it's true petrol GDI units have more expensive fuelling equipment than their predecessors, it isn't operating at anything like the pressure a diesel's does.
The 'one third' figure will be lower now though. Because the total cost has risen due to the requirement of more extensive exhaust treatment componentry. When either of these two systems fail, it's not surprising the repair costs are high.

 

[markjay]

In the original cost, ie the build cost of the engine - the diesel engine's fuelling equipment accounts for one third of total cost. That is massive compared to petrol and while it's true petrol GDI units have more expensive fuelling equipment than their predecessors, it isn't operating at anything like the pressure a diesel's does.
The 'one third' figure will be lower now though. Because the total cost has risen due to the requirement of more extensive exhaust treatment componentry. When either of these two systems fail, it's not surprising the repair costs are high.

I use to contract for the Delphi factory that makes Diesel fuel pumps. It's an extremely complex device that relies on Diesel oil for lubrication. The pump body requires several hours of very expensive precise CNC machining including drilling of oil passages and various access holes (to allow assembly). Looking at the manufacturing process it became apparent why these retail at around a thousand quid each (including distribution costs and VAT etc). And that's before we even got to the injectors and injector rail....

 

[BTB 500]

Because the total cost has risen due to the requirement of more extensive exhaust treatment componentry. When either of these two systems fail, it's not surprising the repair costs are high.

Our OM642 is a 12 year old Euro IV, so simpler than current ones. We've (touch wood) not had any problems with the DPF itself, by avoiding short runs as much as possible. BUT ... we've still had it stuck in limp mode due to DPF sensor failures (differential pressure and temperature). The temp. sensor was seized as well and had to be drilled out (the alternative being a new DPF).

 

[Bellow]

I use to contract for the Delphi factory that makes Diesel fuel pumps. It's an extremely complex device that relies on Diesel oil for lubrication. The pump body requires several hours of very expensive precise CNC machining including drilling of oil passages and various access holes (to allow assembly). Looking at the manufacturing process it became apparent why these retail at around a thousand quid each (including distribution costs and VAT etc). And that's before we even got to the injectors and injector rail....

If/when I ever get around to my Engine Stuff thread - I'll begin by asking why exactly a diesel engine with its piffling little valves and pedestrian rev range needs twin overhead cams - developed from race engines... Repair costs would be significantly lower if the timing gear did not have to be disturbed during head removal. Or that said timing gear in itself isn't the recipient of the repair. (Cams mounted high on the block sides with short stiff pushrods and rockers would suffice - think scaled down industrial units, done that way to reduce operator running costs).
And given that another common reason for head removal is head gasket (itself, 7% of original cost) failure - why, when the valve seats could be inserted and machined from the cylinder side, is monobloc (ie head and block in one piece) construction not employed? Eliminating the head gasket removes that weak link, lowers build cost, improves cooling (and cylinder distortion) and simplifies structural aspects of the block.

Diesel engines and their design engineers are stuck in a rut.

 

[190]

...and while it's true petrol GDI units have more expensive fueling equipment than their predecessors, it isn't operating at anything like the pressure a diesel's does.

Going off at a slight tangent, I'm not convinced direct injection for petrol engines was a step forward other than for improvement of headline MPG figures. In practice I don't believe they are any better than port injection and there is the potential for more noise - in cabin decibel readings went up when direction injection was introduced. While I'm not aware it's specifically an issue for MB engines, direct injection has caused real problems for some manufactures with intake valve deposits as the back of the valves are no longer washed with the incoming mixture. To get around the problem some have resorted to both port injection and direct injection. So just how is the increased complexity and cost justified.

 

[Bellow]

Going off at a slight tangent, I'm not convinced direct injection for petrol engines was a step forward other than for improvement of headline MPG figures. In practice I don't believe they are any better than port injection and there is the potential for more noise - in cabin decibel readings went up when direction injection was introduced. While I'm not aware it's specifically an issue for MB engines, direct injection has caused real problems for some manufactures with intake valve deposits as the back of the valves are no longer washed with the incoming mixture. To get around the problem some have resorted to both port injection and direct injection. So just how is the increased complexity and cost justified.

I'm inclined to agree on all your points.

real problems for some manufactures with intake valve deposits as the back of the valves are no longer washed with the incoming mixture. To get around the problem some have resorted to both port injection and direct injection.

Re the above: I'd change ''manufacturers'' to end user.
Another reason for the twin injectors could be the difficulty in getting the fuel/air mixing and, atomisation completed in the shorter time interval present when injection is solely in-cylinder and begins after inlet valve closing. This has blighted (to some degree) DI in 2T engines. Presumably, the inlet valve deposits can be dealt with by better crankcase breathing - or maybe not...

So just how is the increased complexity and cost justified.

As you allude, there is an economy (and hence reduced CO2 output) benefit - but only at part load (throttle) which is the SI engines Achilles heel re fuel efficiency. But, as SI engines spend most of their time running at part load, then the real world benefit should be present - admittedly with a degree of additional complexity that will add to both initial and running costs.
There is though a SI engine that isn't troubled by part load running (thrives on it) but currently its reputation is not so good. Needs improving. Should be on someone's to-do list.

 

[tangey]

It's been 15 years since I last had a petrol engine. I do recall that a noticeable difference for me when I first went petrol->diesel was that the in car noise at motorway cruise speeds was much less in a diesel, simply because the revs are so much lower than a petrol would be at an equivalent speed.

I guess noise insulation has changed a lot since then, so is this no longer a "thing" ?

 

[Bellow]

It's been 15 years since I last had a petrol engine. I do recall that a noticeable difference for me when I first went petrol->diesel was that the in car noise at motorway cruise speeds was much less in a diesel, simply because the revs are so much lower than a petrol would be at an equivalent speed.

I guess noise insulation has changed a lot since then, so is this no longer a "thing" ?

Hear petrol engines; feel diesel engines? (From inside the car at least).

Diesel 'breathing' is muffled by its (inevitable) turbo and associated ducting leaving mechanical noise to prevail. Petrols are lighter in their mechanical noise but their breathing is more easily audible - and variable as the throttle is used.