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[gimba]

Just trying my luck
Looking to swap my 1.3 petrol for diesel

Bluntly, got to travel 100miles/day
No advisories
98k
2004

More info and proper chat if someone is interested

[Deszus]

Are you sure that you want swap 4 cyl. engine to 3 cyl.? 

[gimba]

Yep, I want better mpg

[Deszus]

Diesel is more expensive to maintain. I have that small Merc diesel called 1.5 CDI and love it but without premium fuel, oil at least ACEA C3 (EGR/CAT very friendly), without adding 2S to fuel, water cleaning top of engine from time to time and using mainly on motorway you can forget about good MPG.

In city 1.5 CDI eats full tank in about 300 miles. Not really fuel friendly.

On other hand... with 5W-30 oil and standard diesel fuel you can easily reach MPG 70 when cruising on highway. 40 viscoity oil, will lower MPG.

Just saying 

[El Tel]

I love my 3-cylinder petrol engine. I wouldn't swap (LHD anyway) but I get why you're looking to economise.

I will say that the 3-cyl ForFour engines are (almost) bulletproof: I've had lots of gremlins with my electrical bits and sensors, but the engine has always been rock solid. Starts first time, every time and never stalls, even when I give it every reason to do so.

edit: it also pulls like a champ - for a 1.1l. Must be the high compression!

[El Tel]

That fortwo image above isn't right for this (ahem) ForFour forum, so here's my contribution to ForFour sticker art:

[Problemchild]

What’s motorway mpg on both?

Then do petrol Vs cost of diesel

This has spreadsheet written all over it haha

JJ

[CrazyG]

Diesel is more expensive to maintain. I have that small Merc diesel called 1.5 CDI and love it but without premium fuel, oil at least ACEA C3 (EGR/CAT very friendly), without adding 2S to fuel, water cleaning top of engine from time to time and using mainly on motorway you can forget about good MPG.

In city 1.5 CDI eats full tank in about 300 miles. Not really fuel friendly.

On other hand... with 5W-30 oil and standard diesel fuel you can easily reach MPG 70 when cruising on highway. 40 viscoity oil, will lower MPG.

Just saying 

Those are only YOUR conclusions....

Maintaining the 1.5 cdi is not expensive....for a start, you don't have to
change 4 spark plugs at regular mileage intervals (B service) as you do
for a petrol..so there's a fair cost saving to start with.
Oil, oil filter, and air filter are the same cost for CDI or petrol.
Ok, so the diesel filter does require changing...but not that frequently
and it doesn't cost much.

And the CDI...if it is used where it really is at it's best, on motorways
or long/prolonged journeys, then you do not need to use top end fuel
etc or any additives as it will be running at optimum temperature, plus
the EGR will do the job it's supposed to do without any problems.
It's short journeys that are 'The Enemy' of any diesel.

And as for fuel mpg...(Autotrader figures for manual 454)
Engine             1.1           1.3           1.5           CDI 95
Urban            38.7mpg    36.7mpg   36.2mpg    47.9mpg
Extra urban    58.9mpg    56.5mpg    55.4mpg    72.4mpg   
Average         49.6mpg    47.1mpg    46.3mpg    61.4mpg

So no matter which way you look at it Deszus, your 300 mpg per tank
around town (urban) is better than you'll get from a 1.5 petrol. If you want
even more miles per tank, why not drive a bit more gently or dare I say
stick strictly to the legal speed limit on each road ?  (Boring eh, I bet)

But whichever way you look at it, mpg is related not only to how
one drives, but also to road and trafiic conditions, plus weather etc etc.
Drive like an F1 driver around town and you'll get crap mpg....
drive like a rich man's chauffeur and you'll get a lot better mpg.
It is all relative.
And no car; petrol or diesel; will ever give good mpg if it is only
driven short distances when it never get's up to the proper working
temperature.....fact.

[Deszus]

What really destroys diesels? Yes, short journeys, you're right crazy G.

Question is why. Answer is carbon. Soot in oil, destroy bearings in engine block. Soft, black killer. It always build up quickest and hardest when diesel wasn't bringed to proper working temperature. So means, replacing oil filters more often than on petrol engines and oil, even best possible synt oil, as often as it is possible. I would say 3000 miles in city, and filter in between.

Oil + filter - > Start point miles
Filter -> 1500 miles
Oil + filter -> 3000 miles

Best cheap oil for 1.5 CDI engine and filters aren't expensive. Mann filter 14 quid and low saps 5W30 ACEA C3 maybe 40 quid for 6 liters.
But this is real maintaining diesel in city. If driven on motorways often, soot buildup should be much lower and that often oil and filter changing, not really necessary.

More from my experience what works and is really valuable when driving 1.5 CDI in city. Good size neodymium magnets on oil filter. I have compared insides of my oil filter after 5000 miles without magnets and other one with magnets (same mileage). Hard to believe how much of steel those magnets collect. Even best oil filter has bypass valve which will send current oil in filter back to engine, so those magnets are really essential if you take care about engine on short trips around city. Won't really hurt on motorway.

[Ocracoke]

If you are using a diesel where the majority of the time it is in the city, you really have to ask why you have one in the first place. Short journeys, to be frank, are the enemy of any IC engine.

However, getting back to the original point of this topic, city driving doesn't sound like the sort of driving that the OP will be doing. 500 miles a week sounds more closely aligned with the sort of driving I was doing when I commuted to work, which equated to about 450 miles a week in my 600cc City-Coupe.

If you run the numbers (G, are the numbers here for the manual? The S-As are a little different)...

1.1 - 500 / 49.6 = 10.08 gallons (45.76 litres)
1.3 - 500 / 47.1 = 10.62 gallons (48.21 litres)
1.5 - 500 / 46.3 = 10.80 gallons (49.03 litres)
1.5 cdi - 500 / 61.4 = 8.14 gallons (36.96 litres)

...the diesel, in ideal situations, does make more sense but I'd be more inclined to keep the 1.3 purely on the grounds of the work done to it and it can technically complete a week on one tank of fuel.

[CrazyG]

Sleepy eyes Ocracoke ? 
The mpg figures I stated were for manual 454's... (as stated above them)   
And yes...the AMT (or S-A as some tend to call them) are a tad better.

[Coverman]

Diesels are more efficient than petrol at idle. Diesel is a CI engine, it is petrol that is IC just to be pedantic.

[Ocracoke]

Sleepy eyes Ocracoke ? 

A touch. I see it now.

Diesel is a CI engine, it is petrol that is IC just to be pedantic.

I'll rephrase to account for that - Short journeys, to be frank, are the enemy of any liquefied fossil consuming engine.

[Problemchild]

Yup - roll in EV arrival haha

JJ

[mr singh]

So means, replacing oil filters more often than on petrol engines and oil, even best possible synt oil, as often as it is possible. I would say 3000 miles in city, and filter in between.

Oil + filter - > Start point miles
Filter -> 1500 miles
Oil + filter -> 3000 miles

this may be the reason as to why you think owning a diesel is expensive...