whats the difference?

[turbo]

Have you ever noticed that when re-fueling at a supermarket they sell "city diesel" while most fuel stations sell normal diesel and Shell have their optimax type along with BP who do one too. I read somewhere that there`s very little difference between any of them. I think my Saab runs smoother on optimax but the fuel consumption is no different. Does city diesel harm your engine if you drive up and down the motorway or go on long fast journeys? Does anyone out there put in an additive that makes a difference to their cars performance? I have a Polish friend who was mixing veg oil and diesel 50/50. It was ok until the cold weather arrived!

[HDi fun]

Firstly, don't use straight veg oil, even mixed with pump diesel in any vehicle that has common rail injection. The fuel rail pressures are vey high indeed in such vehicles and any loss of lubrication can see the HP pump to its grave.

If you are using an accredited bio-diesel fuel you still need to check that your car's engine can cope. Modern emission control systems use a particle (smoke) filter in the exhaust system. Periodically this filter regenerates, this process works by increasing the exhaust gas temperature to around 500f. It's achieved by injecting fuel into the cylinders in the latter part of the expansion phase.

cars with such filters usually have a dosing device which adds a catalyst to the fuel so as to lower the ignition temperature of the built up soot particles.

Some additives can interfere with the fuel borne chemical catalyst. It really is a step too far, just to remove the occasional sooty exhaust when the car is swiftly climbing the torque increase between boost off/boost on.

All fuels are not the same. In my opinion, BP Ultimate Diesel is the best available. Supermarket diesel is about as much fun as supermarket meat.

[pgarner]

and whats wrond with 1% ham 99% water

[waynne]

It's lower fat! I blame the Homeophathies for that!

I belive that city diesel is an ultra low sulpher forumulation although I'd be surprised if there was much difference in reality.

Stick with the big brands and you'll be ok. You get what you pay for although this doesn't mean you can use extra virgin olive oil in your tank!

[vicktor]

i use B.P regular diesel but with a splash of millers spf4 car seems to run a little better and has cut down on the soot coming out exhuast.

[HDi fun]

I use Ultimate. Very rarely I have to use standard diesel so millers diesel sport 4 goes in with it

[turbo]

If I go on a long run in my Saab after about 30 mins the engine warning light comes on and the car goes into limp mode. This has been diagnosed as the EGR valve at fault. However today I did a 150 mile round trip with no problems at all, the difference possibly being that I put Shell Optimax in the tank about a week ago. The tank`s about empty now so I`m going to re-fill with the same again and also put in some Millers diesel sport. This is the first time I have had no problems in ages.

[HDi fun]

Originally Posted by turbo

If I go on a long run in my Saab after about 30 mins the engine warning light comes on and the car goes into limp mode. This has been diagnosed as the EGR valve at fault. However today I did a 150 mile round trip with no problems at all, the difference possibly being that I put Shell Optimax in the tank about a week ago. The tank`s about empty now so I`m going to re-fill with the same again and also put in some Millers diesel sport. This is the first time I have had no problems in ages.

1. Shell Optimax is a petrol fuel - clearly you're not putting this in as it's no longer available, having been supplanted by Shell V-Power.

2. Does your car have a particle filter? These have a finite lifespan, generally around 50,000 miles after which they need to be replaced. The latest versions are apparently maintenance free. When my car first needed the DPF replacing it was indeed at just over 55,000 miles. The regeneration process seemed to occur more often and took longer each time leading up the eventual failure of the component. Be careful how much you pay for this job. You also need to get the additive reservoir replenished and I recall that there is requirement for the ECU to be 'notified' that the job has been carried out.

Most independent diesel specialists don't have the knowledge of such systems so let a Saab dealer or Saab specific specialist do the work.

[turbo]

Yeh, Shell V-Power, thats the one. The valve in the EGR valve sticks. Its a common fault on this GM unit. I did strip it down and clean it which helped but it did still play up every now and then until yesterday and I wasn`t hanging about! As for the particle filter...........not too sure but it probably has one. It` worth looking at. I`m off tomorrow. Cheers

[HDi fun]

I think it's the same engine as found in the Vectra CDTi models, along with Alfa Romeo diesels. What year is your car? Most before 2004 don't have particle filters (which is nice); strangely my 2001 car does have one! It was Peugeot's early attempt at a smoke free diesel. And it works. But I'd rather not have the complexity associated with it.

If your EGR is causing problems try a bottle of Forte Diesel Treatment in the tank with about 2 gallons (70-90 miles) left. Drive it for twenty minutes quite savagely. Then refill with diesel, thus allowing 1, A quick concentrated cleanse; 2, the rest of the tank at the normal dilution. Do not add Milllers Diesel Sport at the same time! Make sure you avoid the old MIllers Diesel Power Plus if your car has a particle filter - it is NOT compatible with Euro IV diesel engines.

Forte can be found on Ebay quite cheaply, should be able to get one for a tenner, inc delivery.