Why are diesels are suited to motorway miles?

AdrianC

sevenhills wrote: »

Why are diesels are suited to motorway miles?

DPFs do not like constant short journeys, never getting hot, and clog in short order.

In the old days, petrol cars had a manual choke, I guess they still do the same thing, but controlled by the cars computer.

The "choke" has been automatic since the 80s on most things - initially through a waxstat on the carb, but injection simply takes coolant temp into account when deciding the fuelling. Petrols like a richer mixture when cold, so the choke on a carb restricts air intake. Injections simply inject a bit more fuel. But, once they're even slightly warm, everything post-cat introduction in 1992 is run at the optimum fuelling.

Do diesels have some form of choke that makes them more suited to longer journies?

No, they simply adjust the injection timing a bit. All diesels are injected, always have been. The air going in is unrestricted, so there's no "choke" in the same way - on a petrol, the throttle increases air, and fuel increases with it. On a diesel, air is unrestricted, and the throttle increases fuel.

I have just bought a Euro 5 1.7 diesel Zafira, so with my low mileage...

Oops.

Nasqueron

Diesels can work on low mileage if it's mostly motorway driving, if you're just going to the shops etc you'll knacker your diesel

sevenhills

Herzlos wrote: »

Diesels tend to be more efficient with more low down torque.

I did notice that the quiz asked if you were the type of driver to put your foot down, so maybe they are not suited to Boy-racers.
I plod along and take my time.

sevenhills

AdrianC wrote: »

DPFs do not like constant short journeys, never getting hot, and clog in short order.

If you are aware when the regens will take place, then maybe that can overcome some issues.

sevenhills

Mercdriver wrote: »

Reading that makes asking advice about a car you've already bought a bit like checking flight prices after you have bought an inflexible ticket. Unfulfilling and ultimately painful.

If you read all the stories about diesels, no one would buy one :j

Mercdriver

sevenhills wrote: »

If you read all the stories about diesels, no one would buy one :j

I don't believe everything I read, but this one isn't just a myth. You will have to find a way of adapting your driving to make it work...

chrisw

sevenhills wrote: »

I did notice that the quiz asked if you were the type of driver to put your foot down, so maybe they are not suited to Boy-racers.
I plod along and take my time.

I was always told that diesels are better suited to being driven fairly hard rather than plodding along. But hard doesn't necessarily mean high revs.

They tend to clog the piston rings and soot up the passageways if driven too gently.

DUTR

chrisw wrote: »

I was always told that diesels are better suited to being driven fairly hard rather than plodding along. But hard doesn't necessarily mean high revs.

They tend to clog the piston rings and soot up the passageways if driven too gently.

The thing is do you buy a vehicle to suit your driving needs or to adapt your driving to suit the pros of the new vehicle?
Some articles are showing that derv returns about 10-15% greater mpg, however it's not as if modern petrol are that thirsty driven under the same route and conditions.

a.turner

Let's see how long it lasts as him minicab.

sevenhills

a.turner wrote: »

Let's see how long it lasts as him minicab.

Most taxis seem to be diesels, short and long journies; but I guess the engine is always on the go and very hot.