Having read the 'Fuelstar' thread and Neil Brownlee's pointer to "Tony's" fuelsaving web site (hereafter referred to as 'Tony') with some interest I feel it's time to give my final opinion as promised some time ago on Hiclones.
Firstly, to recap, I do not drive a vehicle with heavy feedback controlled emissions so this will have a bearing on the results. I run a cobbled together 3.5 carb V8 so no, the fuel burn efficiency is not going to be optimal however much I try. Tony is correct when referring to modern engine thermodynamics but I'm talking 50 year old engine designs here! I did not purchase the units - they were given to me by a dealer FOC in exchange for an honest test (which I insisted on before taking delivery) and I submitted results for it last year. I have continued to test the units to satisfy my own curiosity more than anything.
Ok then, on to the nitty gritty.
Firstly emissions. CO and HC emissions both dropped significantly when Hiclones were fitted as measured on a commercial emissions tester. Figures are available but not really relevant for these comments.
MPG figures as Tony rightly comments are a pain in the proverbials to measure accurately on the road. I have been testing these things in various configurations for the last year so I'm not basing this on a tankful. However according to my figures both with and without hiclones and also with hiclones in different inlet positions I noticed an increase of 1-1.5mpg with the units fitted. Without Hiclones I get between 15 and 16mpg, with I get 16-17mpg and have achieved 17.8 on two occasions ... not large but statistically significant.
Both emissions and mpg figures were measurable results and, more important, fundamentally repeatable. I make no comment about why the results are as quoted only that they are. I have absolutely no way of investigating *why* they produce those results so don't ask me to speculate as whatever I think is irrelevant.
The final comment is one that I originally refused to make. I always said I would not give a 'subjective' result i.e. one not based on hard figures. However I've changed my mind as I had to find a way to demonstrate the before/after difference to myself! Basically I felt that Hiclones give me more very low down torque. Again I can't explain this but I can demonstrate it with the Hiclones by being able to negotiate a certain fairly tortuous route around a housing estate with little to no throttle whilst in top gear and overdrive engaged pulling from under 600 revs ... Without the units she'll just about pull the top gear from those revs but not the overdrive ... don't ask me to explain why.
So my summary would be that in my test vehicle, with the conditions under which I tested the units I found them to give positive, repeatable results with respect to emissions, mpg and low-down torque.
Are Hiclones worth their cost? Well, I think they are silly money and personally if I had to buy them I probably couldn't economically justify any saving they make. However, until somebody shows me how to get the torque from my motor that I'm getting now *without* Hiclones they're staying in!