Here are the latest results in terms of using these magnets:

The car is a 1994 Audi 80 Saloon equiped with a 1.9 TDi rated at 90 HP
(in fact 105 HP) running on diesel fuel.
The car has 230 000 km.

Beforehand, without the magnets, in the UK, the car was doing from 7
to 7.2 L / 100 km on motorways.
I had checked that several times on trips to the outscirts (fair
centre) of Birmingham, Manchester
and Liverpool airport starting from Lancaster.

I have driven 4500 km throughout Europe and Turkey from Lancaster to
Morphou in Cyprus
with a heavy car fully loaded including a 450 L roof box and it did
6.5 L / 100 km and
this includes crossing several mountain ranges, driving nervously in
french, italian and Turkish cities as well.
We could say that we were on mixed driving.

I have now completed a test mostly on motorways around Cyprus but also
including city driving in Lefkosia
and the car did just below 6 L / 100 km.
We can say that the magnets have reduced the fuel conusmption by just
more than 14 %.
If you read the magnet documentation, they advocate savings around 15
% which means that I have reached them.

Apart from that I can really appreciate the added punch that the
diesel has now in the low revs which means that city driving is much
more pleasant.

Therefore, I do conclude on these two lines:
1- these magnets are really functionning as far as I am concerned and
I will keep them
2- there is enough evidence to go further with investigations, I set
up a lab demonstration
to launch my own instrumented tests and publish them in the open
domain
(that is the role of free public Engineering Schools)

Now, it is up to you to decide if 30 euros is worth spending on a
device that can add punch (meaning more HP) and also save up to 14 %
on your petrol bill.

Luc Rolland