Additives

i find that when i run my motorhome on germant bio-diesel (bought from the pumps over there) my van gets 2mpg more than on dino diesel, (which is a lot when your talking 20mph to start with, and 150 litre tank) i can feel she wants to go more on bio-diesel, so i use less throttle, engine is quieter too, and that lovely frying donuts smell from the exhaust.

Possibly, but I doubt it. Valve faults can sometimes be attributed to fuel certainly, some head gasket problems too, but most often they are due to a previous overheat, sometimes not showing for months or years, but usually there is a previous instance of a known overheat. Some of the egr blockages are due to fuel, dirty throttle bodies are sometimes definitely fuel, worn diesel injectors, fuel pumps etc. etc. There are so many vulnerable bits in an engine that it is not worth the few pence a tank full saving to buy cheap fuel. Cars are a bit like humans, you put junk in and you get poor performance and reduced life in the long run. Unlike humans, cars cannot self mend at all, any damage is there for ever and is cumulative.

You keep using cheap fuel, I'll use better stuff. How wonderful there is a choice. If everyone used good fuel I might get less work, so maybe I should recommend the nastiest stuff made, which I believe is Q8.

That is a great improvement and worth paying a bit more for. The engine will run a little easier too, so should last better.

Most of my vehicles are petrol powered and there doesn't seem to be any great change in mpg, (I do not study it that closely), but, they do seem to run nicer on branded fuel.

On Tue, 17 Feb 2009 14:20:43 +0000, Mrcheerful spouted:

Eh? Last time I looked, injectors are downstream of the throttle bodies..

Mike

They are on multi injector engines but not on CFI installs, you can even run the engine and watch the fuel dripping in if you want to.

I bet they charged you about £30 for the additive? I also bet they buy the stuff by the box load from a salesman/white van man at circa £2 a shot.....

I'm of the opinion that you don't need this ''snake oil'' stuff, unless you have a definite problem. I base my opinion on owning three Diesel cars, one covered 300,000 miles before sale, one is on 220,000 miles and one was sold a while ago on about 170,000 miles. None of these engines ever had any work done on them except cam belts and oil/filter, and all sailed through their MOTs with the obligatory pre-MOT thrashing every year without a problem. (XUD(T) engines 1.7 &1.9)

Julian.

And lubricity enhancer in the shape of ATF Dextron - recommended by some manufacturers.

Julian.

Stephen presented the following explanation :

It suggests using the additive once per 4K miles. The bottle had 4x doses and cost me £7 - £8, but it has saved much more than that in improvements in fuel consumption.

Conor brought next idea :

Without actually checking - the STP bottle suggests about 100ml once every 4K miles.

Yeah you're correct about the cost and the car has only 8500 Kms done so I reckon it wasn't needed either. Something I'm a little more concerned about is the fact that they overfilled the oil somewhat...about the equivalent of two notches on the dipstick. I'm not sure how much this equates to but should I have some oil removed?

Patrick

overfull can (some engines it makes no odds) be bad for the engine and emissions,

It happens that Patrick E. King formulated :

Too much is as bad as too little. The lack of air space above the oil can put extra pressure on oil seals and cause damage. Get them to remove it.

Odd. Every liquid-cooled vehicle I've ever owned used the radiator pressure cap to regulate cooling system pressure, typically to about one bar above ambient but it varies between vehicles: the header tank is just that, a tank. Most operate at ambient pressure, or near as dammit.

Are you sure the leaky header tank didn't cause the coolant to leak out, resulting in excess air getting drawn into the system? That could cause overheating and can result in head gasket failure.

Exactly, if your HG can't take the coolant pressure then it won't like tghe oil pressure & god help it with the combustion cylinder.

Pip Luscher gurgled happily, sounding much like they were saying:

Just remind me where that pressure cap IS?

Ah, you were talking about the top tank on the radiator itself? even so, the pressure cap, not the state of the tank, determines cooling system pressure unless the cap itself is faulty. And that pressure is very small compared to the CC peak pressures (and oil gallery pressures for that matter), as has been pointed out. Also, don't you think that the hoses, radiator, water pump seals etc. are far more likely to let go before the head gasket?

If the header tank is on the low pressure side of the system it isn't a header tank. It's an overflow device. Unless you'd care to give an example?

There are two main systems, one where the whole lot including the remote header tank is pressurised, the other where the radiator is pressurised and has a pipe to leak off hot coolant and draw some back when cooling down. Japanese cars usually use the latter. Ford, volvo, vauxhall and loads of others use the 'whole lot pressurised' approach

Thanks for the info. I've had them drain some off. Regards Patrick