... it was the injectors.

[Peter.N.]

Some of you may remember me droning on about the fuel consumption of my recently acquired 406 Hdi estate some years ago, it would always give me 60 + mpg on a long run but the two I have had since that one got written of by water in the electronics have only ever returned about 55 mpg. I put it down to defective calibration.

I have tried all sorts to improve matters on the ones I have now but to no avail, Maf, checked camshaft timing as I changed the belt last year but almost spot on, changed the fuel pump pressure regulator, no change at all.

Before we went on holiday a couple of weeks ago I tried changing the injectors over with the ones in my original car, now my spares dept and believe it or not I got an immediate 5 mpg or so improvement. This car has done 210,000 miles, the one I removed them from had covered 246k although the injectors looked cleaner than in mine.

We did nearly 2500 miles around the north of Scotland and Yorkshire and averaged, according to the display 62.4 mpg, the actual measured consumption was nearer 60 mpg. I filled the tank at Asda in Tain and it took 69.1 litres for 924.5 miles and was still showing one section of the gauge although the light was on, I reckoned I could have done 1000 miles if I had been prepared to take the chance. The fuel was also 8 or 9 p cheaper than anywhere else in Sutherland that we saw.

I'm not suggesting that everyone can get this sort of economy as I rarely drive above 60 mph or 2000 rpm and most people would probably be bored to tears but it shows what can be done and not to ignore the obvious. It seems that the greatest improvement in economy comes at low throttle openings as although the consumption drops sharply on steep hills it recovers more quickly now on light load than before.

Well it though it might interest someone.

Peter

[lexi]

Good going Peter. Some engines, those 8 valve with proper Bosch fuel injection. I somehow don't think the later Delphi systems are as good.

[Peter.N.]

Mine is a Bosch but I foolishly concluded that as it sounded OK and wasn't smoking or knocking the injectors were alright. I suspect that they weren't atomising properly at low input volumes.

Peter

[white exec]

That's a brilliant bit of economy, Peter - and what better place to do it!
I last paid about €70 to have a set of 4 Bosch injectors serviced/reconditioned/recalibrated by a Bosch-Delphi service centre in Malaga, which I thought was good value. Not sure what the cost would be in the UK.

[Pug_XUD_KeenAmateur]

Defo of interest Peter, my motorway speeds have been creeping up of late with the old girl loosening up.

I should remember this next time I'm thinking "Shall I overtake, or shall I just ease off and drop in behind [any given vehicle]"

[EDC5]

Good going Peter. Some engines, those 8 valve with proper Bosch fuel injection. I somehow don't think the later Delphi systems are as good.

Can you expand on this a bit? Are you referring to the Delphi injection system fitted to the 16V version of the 2.0?

[lexi]

Just that with Delphi stuff in general, it doesn't seem as good. Quite a few Renaults I have been involved with have had many issues with Delphi systems, as in injectors etc.

[moizeau]

Peter, was this the 'sluggish' one? Great news if so.

[Peter.N.]

Strangely enough the performance didn't improve a lot with the injector change but it has since we did our 2,500 mile holiday trip.

Peter

[Paul-R]

As a lover of high MPG figures Peter you'll appreciate our trip to London and back yesterday in the 308. Took youngest daughter to her digs together with a surprisingly large amount luggage, books and stuff. No brim to brim result yet but going from the display figures as follows:

Filled to brim, reset mpg trip and then did about 50 miles locally over the weekend. 70.5mpg

Drove down M6, M42, M40, M25 and M4 to London. Stuck to 65mph max on the cruise control except for the (rather long) sections of the M6 limited to 50mph. At the end of the M4 in London the reading was 74.2mpg.

Destination was Herne Hill, south London and so average mpg dropped to 72-ish.

Return trip through London was at the start of the rush hour and, by the start of the M40, the reading had dropped back down 70.5.

Return trip from there on was actually easier than going down and when we got back home the reading had returned to 74.2. Total mileage about 500. Imagine what you could do in this car!

[Paul-R]

The results are in. 539.2 miles and it took 28.62 litres (6.3g) to top up. That makes an unbelievable figure of 85.6mpg! The station I just used has a slight incline on the concrete surface and so I suspect the tank could have taken a little more but even if you add another 5 litres (unlikely) to the figures that still gives an average of 72.9mpg.

I am well impressed with this car.

[Peter.N.]

Brilliant! I assume that is the 1.6 engine. I would love have to have that sort of mpg but I think that the fact I probably couldn't repair you car myself would negate any fuel savings I might make.

Peter

[Paul-R]

Yes it is the Blue Hdi 1.6. Which chucks out an incredible max of 120BHP at an impressively low 1750rpm. This makes it feel like a much bigger engine than it really is and will pull quite strongly at stupidly low revs.

Yes, there are bigger bills to come I'm sure but £0 road tax helps take the sting out of things. There's the extra expense of AdBlue liquid every 12-15,000 odd miles but that's cheap. And then a fill-up with Eolys a few years away with DPF cleaning/replacement a good few years after that.

The car is so good that I find myself driving it more than the C5. It's not that the C5 is no good all of a sudden but you can't argue with fuel consumption normally 30% better and, on the figures above, this time 60% better! It's also nice and nippy if you need it and good fun to drive.

That would explain how we manage to put 15,000 odd miles on the 308 last year and only about 5,000 on the C5. I must get round to altering the insurance details on both cars!

[EDC5]

That is truly amazing economy! I can get just over 50mpg on a motorway run at an indicated 75, so I cant complain about that. Could possibly get more at 65 but I don't have the patience.

but its good to see that the 308 actually exceeds 70mpg. I bet it doesn't drop too much around town, where in the C5, it drops like a stone

[Paul-R]

My wife can get the average down to the high fifties without too much problem! When I drive it around town it's usually low sixties.

When I filled the car up at lunchtime she then took the car off me to go to her lacemaking classes. I'll take a look at what the reading is when she comes back. A lot will be on the motorway and then some around town so I would hope low sixties.