Fuel Additive surprise

I know this crops up every now and then, but hadn't expected that, on adding the appropriate measure of millars (2003 td5 110 with 100K on) because I thought cleaning the injectors a bit might be a good idea (how do these cleaner reckon to work?) I was suprised by an instant improvement in low-end performance. Clearly, the additive is raising the cetane rating.
I'm finding that the slight hesitation at low revs, when changing gear or setting off is removed. The vehicel now accelerates quite happily from 30mph in 5th (on the flat) - I always had to change to 4th to do that.
I'm also finding improved fuel economy - quite definitely, though I haven't precisely measured - but travel same route every day and know from experience where the fule guage will be after each 50mile journey. This improvement is very likely down to a drastic reduction in gear changes on corners and hills.

What I'm not finding is any improvement in revving - and that might be down to something else (binding wastegate actuator, mucky MAF, atc) - the vehicle was always 'reluctant' to rev - it 'wants' to change out of 3rd at 30mph, out of 4th at 40-45 mph, and, whilst now blissfully quiet at 50 -55mph, the engie noise gets a bit thrashy at 60-65.
IN fact, given a long enough airfield, it will actually climb through 75 upto 80+ (on the clock) but it's bloody noisy.

So now, with the improved bottom end, it has a power band that is usable, but still narrower than (I feel) reasonable.
My old 2002 '90 that was prematurely 'recycled' by we_pike_anycar.com was more willing - though it had no cat +straightthru centre pipe. You could hear the turbo whistle for miles - I can't hear my current one at all (though it must be working, or it would never reach 70, I'm sure)

So I'm thinking that the additive is working at the moment, not because of cleaning but through increased cetane rating, but this has more effect at low revs and the advantage is neutralised at higher revs by the engine's inability to take advantage of it
I wonder if a boost gauge could tell me more?

I had very good results on other marques of motors with the millers diesel additive, never bothered with the landy though as its not my daily just a toy, good to hear your having a decent result from it, enjoy

Well, I decided to experiment, and not put additive into the next tank full.

I got about 10 miles, and in exasperation, stopped and put a 50ml treatment in again.

The old lethargy at low revs was back. I had to work the box to get up to speed.

After the treatment, about a couple of miles along the road, the new low end pulling power had returned. At varying speeds, between 35-40mph and and 60+ mph, it was like driving an automatic.

So the effect is certainly not down to 'cleaner operation' (which, according to the instructions, should ensue after about 200 miles - but I had done 400), so must be down to increased cetane rating..

So it looks as though a £90 fillup needs a £2.50 shot of additive to run nicely.

The question is: do I actually make that up in increased fuel economy?

My next task is to measure, with and without, a tankful each time, taking the same journey each day.

Will post result in a couple of weeks.

I'd guess you have a compression problem (rings or valves) and the additive is compensating by making the fuel mix burn easier. JMHO

What other symptoms of compression problems might I see? (starts well, every time, doesn't smoke, idles fine...)

If you take the dipstick out and run the engine at idle are you getting puffs of smoke or vapour from the dipstick tube? Are you seeing the same from the cam cover oil cap? If so you have blowby of the rings on at least one piston which will affect power output but not necessarily starting or idle.

Valve leaks are harder to track down without taking off the exhaust or inlet manifolds. You are looking for wet oil/diesel in the exhaust manifold (partial combustion) or soot in the inlet manifold.

I reckon it's purely down to imagination.

Rob - I'm a scientist, so you can imagine what I make of quack claims and makebelieve science!

I've reasonable evidence that something is going on, and my next step is to quantify that. My initial estimates place the economy gains in excess of 10% - but I'm immensely skeptical (if it were that easy, everyone would be doing it; there's no such thing as a free lunch)
A better explanation might be, as shifty suggested, that there was some pre-existing reason for suboptimal performance. I was getting a very consistent 26-27 mpg - country use, up and down the box, but no high-speed (!!- well, you know what I mean) cruising, and very little town work.
So, even for a 110, driven not lethargically but no pulling wheelies, that mileage was on the low side.
In other words, if the raised cetane level is, in this case, compensating for some other performance deficit, that would not translate to some universally-available magic bullet.

That might explain why, if I try sticking it a bit, there's no improvement in acceleration at higher revs - where this particular vehicle is, if not terrible, slightly reluctant and noisy.

I'm not (yet) observing any symptoms such as Shifty suggests, though the valve thing is obviously more complex.

sparg said:

Rob - I'm a scientist, so you can imagine what I make of quack claims and makebelieve science!

I've reasonable evidence that something is going on, and my next step is to quantify that. My initial estimates place the economy gains in excess of 10% - but I'm immensely skeptical (if it were that easy, everyone would be doing it; there's no such thing as a free lunch)
A better explanation might be, as shifty suggested, that there was some pre-existing reason for suboptimal performance. I was getting a very consistent 26-27 mpg - country use, up and down the box, but no high-speed (!!- well, you know what I mean) cruising, and very little town work.
So, even for a 110, driven not lethargically but no pulling wheelies, that mileage was on the low side.
In other words, if the raised cetane level is, in this case, compensating for some other performance deficit, that would not translate to some universally-available magic bullet.

That might explain why, if I try sticking it a bit, there's no improvement in acceleration at higher revs - where this particular vehicle is, if not terrible, slightly reluctant and noisy.

I'm not (yet) observing any symptoms such as Shifty suggests, though the valve thing is obviously more complex.

Click to expand...

Well if you're a scientist have you done any research into snake oil, bloody wonderful stuff it is.

Strictly speaking, the calorific value of snake oil varies with species; cold water species have significantly higher values on combustion than tropical species; however, the relationship is by no means linear, and there is statistically significant overlap between populations.
In any event, as a convertible fuel additive, in the light of current technology, reptiles are probably inferior to many more amenable sources....:fencing:

Well played, Sir!

Anyway, I have no reason to believe any of the info from various sources. So called scientific studies turn out to run under pretty ****-poor standards.

It would be interesting to see a good study.

sparg said:

Strictly speaking, the calorific value of snake oil varies with species; cold water species have significantly higher values on combustion than tropical species; however, the relationship is by no means linear, and there is statistically significant overlap between populations.
In any event, as a convertible fuel additive, in the light of current technology, reptiles are probably inferior to many more amenable sources....:fencing:

Click to expand...

That's a bit more like it.

...and of course, relatively somnolent constrictor species that eat grossly but infrequently, store energy in the form of convertible hydrocarbons, whereas so-called venomous species, relying on speed for hunting, have proportionately smaller fat stores...
blah blah, drone drone...

Seriously, the basic scientific principles apply: no there's no such thing as a free lunch, and if it looks too good to be true...one's probably made a mistake in the measurements.

Fuel additives have a long and honourable history of bo**ocks claims. Some actually have more substance than others
back in the '70s, stock car racing, we discovered nitrobenzene. Marvellous! but the downside became apparent after a couple of races - in the form of conrods sticking out of unexpected places.

I favour, in this case, the probability that the additive is actually compensating for some deficit (and that, in the absence of such a deficit, the advantages would evaporate) - if that were the case, then the question is really about what deficit there might be.
Compression problems have been suggested, poor quality fuel could be a suspect (though as performance has been remarkably consistent with fuel from France, Spain and various UK sources, that likelihood seems diminished), or some combustion inefficiency (injector seals, lost injector codes at ecu etc).

I've previously said that it seems probable that economy gains are largely associated simply with restored torque at lower revs meaning that gear changes (5th down to 4th, 4th down to 3rd) are less frequent - this seems more likely than some kind of improved overall efficiency of the power plant. If that were right, then I should see little or no improvement on steady 60-65mpg cruising on motorways (I usually get 26-27 mph very reliably). I can't test that just yet.

I certainly wouldn't want anyone to infer that banging some of this stuff in the tank will naturally mean a 10%+ improvement on fuel economy - if your td5 is running right, then it's likely you would barely see an improvement of 1 mpg. I can only report what I've observed so far.
cheers

Update



The results I've had over 2 tankfuls, just under 900 miles, - 31.266 mpg.

I've said before that, short of cruising at a steady 50 mph all day, the sort of mileage I do is probably the gentlest sort - not slow, but the majority of the journey is between 30 and 60, only about 15 stop /give way junctions (though I certainly use the accelerator appropriately). It's a double cab p/up 110 td5 with 120K on clock.

Unfortunately, I don't have quite as precise figures for consumption on the same roads without additive. However, I do now when I had to fill up, and I'm certainly getting an extra 40 miles (conservative estimate) per tank, and my estimated consumption was 27 mpg.

that would mean better than 15% improvement!

Next, I want to try a Bearmach tuning module I've just agreed to buy, to see if it gives me a similar power/torque performance.

In the meantime, if I can bear to go back to the old sluggish setup for a tankful, I should try to draw some more precise figures for the non-additive state.

Keep us posted!

It would be interesting to see how this compares in various conditions.