[groar]

In the megane, a 1997 1.9 turbo diesel, I can see a difference when the car is cold : with low grade diesel the starting is harder and the idle is unstable a few moments. Also the engine doesn't accept low rpm : 1350 instead of 1250.

In the high grade I'm using, there is around 10 additives and some to clean the engine. Before I use that high grade diesel, the engine couldn't accept to stay at a stable 1500 rpm. During the first high grade diesel tank, it accepted to stay at 1400 rpm and also to accelerate from there.

People are saying that this high grade make less noise, but I didn't eared that as the engine is relatively silent at low rpm.

In the scenic, a 2001 1.9 common rail turbo diesel, it doesn't seam to make a visible difference.

About your 83.1 MPG, are they Imp MPG or US MPG ? If these are US MPG then you should train to beat the world record... Even if these are Imp MPG (ie 69 US MPG) then your result is great as you are saying that you are not driving specifically to save gas.

In France your C3 (1.4 HDi 70 sensodrive) is rated at 54.7 US MPG combined, ie around 65.7 Imp MPG, you rated yours at 64.2 in your garage. On highway it's 60.3 US MPG (72.4 Imp MPG).

Are your trips mainly city, highway or combined ? How long are they ?

The front grill block is an easy mod and it permits to heat the engine quicker and to keep it warm longer when it's stopped. In England it should make a big difference. Currently without grill block my engine doesn't heat during my 20 miles commute and we are not yet at the sub 0°C season here...

Denis.