[paulgato]

Hi Steve, so you still have the SDi then. I'm jealous. No turbo, no intercooler, no temptation to step on it and use more fuel. Less weight, more space in the engine bay. Less to go wrong. Nice. Not so many SDi's around in the UK.

Actually, since you don't have an intercooler, I think you can block off the lower grille completely - and I would suggest semi-permanently - with no issues at all. Mine is in fact blocked with plastic sheet secured by black PVC insulating tape (it's a black car so it looks fine) but I realise that it blocks the cold air from the intercooler, which might not be ideal. The way I drive though, I so seldom use the turbo that I think it probably makes very little difference in my case. (I blast the engine briefly once a week or so just to blow any soot out and to make sure the turbo parts (vanes?) don't seize up.)

If you have Scanguage (I don't at present) then you will know what temperature your engine coolant gets to. Does it stay up at the correct temperature (90+ degrees) with the grille open? I guess it might do in the summer. Over last winter I had the grille completely blocked (apart from the engine air intake of course!) and that worked fine for me. I did experiment with keeping the 100% grille block in the heat of the summer, and although the engine coolant temperature never rose above 100 degrees even when it was 30 degrees outside (I use VagCom to measure) the air temperature in the engine bay rose to over 50 degrees at times and I decided to unblock just the uppermost row in the main, central, upper grille, just for the summer. Come the autumn, it will get wrapped up warm again until late spring. Maybe different engines behave in different ways but for me that's the only way to get - and keep - the engine up to proper temperature in winter. And that makes a quite marked difference to fuel economy. (And no, there's nothing wrong with my thermostat - the engine simply doesn't create much heat!)

Your mpg for a steady 70mph, by the way, sounds astounding. My mpg is great up to 50mph and then drops off markedly even at 55mph. Sounds like the lowering really did work. It occurs to me that the new suspension components might just work better, and create fewer momentum losses, simply because they're new - or that may be a part of it - but 70-88mpg at 70mph is very impressive. Fortunately for me, I am entirely happy to drive slowly most of the time and 50mph is a perfect motorway cruising speed for me. For that reason - and for the reasons of both cost and comfort over speed bumps - I think I won't lower my suspension, but for most people it seems it would make a huge difference to economy. Whatever happened to those Citroën cars with the active suspension that you could lower and raise at will? That would be ideal.

As for the 'gentle-acceleration-vs-brisk-acceleration' question, well yes, I have tested that. I have a 50mph circular route that I use for testing the effect of mods on mpg. It's about 10 miles total: a rolling start at 50mph on a local dual carriageway. I zero the mpg meter as I pass the start location, drive the 5 miles at an indicated 50mph using cruise control, then slow down for the roundabout at the end, stopping for at least one of the three sets of lights on the roundabout, accelerate up to 50mph again for the return leg and maintain that until I pass the start point again, at which point I note the reported mpg average for the circuit. (I use the car's normal mpg display. Not accurate I know, but consistent enough for an A/B, before-and-after test of percentage difference in mpg following a mod. The display will read between 95 and 99.9 mpg these days. Less in winter. (The display seems to be about 6% or 7% over-optimistic overall. On my next really long journey I'm going to check exactly how optimistic it is at 50mph. I suspect it is less optimistic than at slower, city speeds.))

Obviously a significant part of the fuel used in that loop is for accelerating up to 50mph again after stopping, and I have experimented with different accelerating styles, including letting the cruise control get up to its set speed again on its own. My conclusion is that very gentle creeping up of speed is not good because even gentle acceleration uses far more fuel than steady cruising, and creeping up the speed just prolongs the extra fuel use. Aggressive acceleration, or even very positive acceleration (difficult to describe exactly what I mean but I hope you get the gist) is TERRIBLE for fuel economy - the average goes right down and doesn't recover. What works best is fairly gentle but positive acceleration, and getting into top gear as soon as possible consistent with that definite acceleration. In fact, kind of 'normal' acceleration works best. (Think typical minicab driver style?)

At present my engine is in a remapped state - having had it remapped on a 'like-it-or-money-back-and-your-original-map-restored' basis. I did explain that I was interested only in mpg improvements. Disappointingly, it has increased my fuel consumption slightly. Slightly but definitely. Even on a steady 50mph or 55mph route on a flat road, the fuel consumption is significantly up, and overall, tank-to-tank consumption is up by a good few mpg. A shame. I had put a lot of hope in getting a remap. The car drives better of course - much more torque, to the point where 5th gear feels like 4th gear used to feel - but for me that doesn't help much and actually makes it harder to drive economically. I will get it put back to standard as soon as I can arrange it.

Just to be clear, did you change your gear oil? If not, I can highly recommend it. A bit unscientific in that I put the Molyslip in at the same time as renewing the ten-year-old gear oil, but wow, what a difference it made!