Anyone claims they're getting 90+ MPG out of one of these in *normal motoring* is talking out their bottoms. The 308 110 HDi holds the world public road fuel consumption record, and being driven for. Week in uber-granny mode failed to do much more than 90.
Your figures are about par for a normal geezer driving the worlds officially (as in ratified by Guinness) most economical real world car. ( As opposed to bullpois bench-test government figures).
I've just got 612 miles out of a full tank of diesel in my 308 HDI Sport before the warning light came on. This is doing a mixture of motorway and around town driving, according to the computer I’m averaging 52 mpg, I agree 90+ mpg is totally misleading.
Peugeot don't claim 90MPG, so they're not misleading anyone. I get a rock solid 52/53 MPG combined out of mine, but going to my Dads in Kent, 120 miles, 115 of which are motorway, returns a high 70's average if I stick religiously in the 60-65 speed range, which isn't difficult if the traffic is heavy but moving well. Pug claim 74MPG on the extra urban cycle, so that's pretty nmuch on target.
Remember - that's *** Extra Urban ***, not combined, so you won't see that figure in your daily motoring. Pugs advertised figures for the 308 are, for a change, refreshingly accurate.
Our 1.6 THP has averaged 7.0 litres per 100 km over 53,000 km according to the trip computer (that's 40.5 mpg to the Imperialists).
I note though that the speedo is 5% optimistic - if this translates to the odometer, then that would be 38.5 mpg.
Quite happy with that, noting though that we pay a premium for 95 and 98 RON over here, compared with 91 RON regular unleaded (about an additional 6% and 11% respectively). I normally use 98 as it has a higher energy density than 91 and 95 (which are equivalent, although Australia is gradually replacing regular 91 RON with E10, which has even lower energy density)
98 RON contains no more energy than, say, 95 or 93. The calorific value, the amount of energy per unit of fuel is identical.
However, 98 RON will have a greater resistance to pre-ignition than a lower grade. Therefore, it is possible to compress the charge more, ie, run a higher compression ratio. Running a higher compression ratio is inherently more efficient, and creates more power, and although a higher octane allows the fuels energy to be extracted more efficiently, it actually contains no more energy than a lower grade.
I'm very anal about fuels, having written a lengthy dissertation about rocket fuels for my Masters.
PS - that is indeed a very respectable MPG for a THP.
Hah - I'm a victim of advertising yet again! I recall looking into this some time ago and major producers in Australia (eg Shell and BP) claimed higher density for their 98 RON product.
I see that this claim has now been dropped from their web sites, although they do claim better economy and performance for them (better combustion and reduced friction). Eg:
w w w.bp.com/sectiongenericarticle.do?categoryId=9015032&contentId=7028158
References to higher density can still be found in some of their search engine results, but clicking on resultant links reveals no text to this effect. One that might have slipped through is the 'Is It Right For My Bike' tab at:
w w w.shell.com.au/home/content/aus/products_services/on_the_road/fuels/shell_vpower/overview/
(third last paragraph)
Interestingly, I'm now averaging 58.7 in mixed motoring in my 3008 with the same engine and 6 speed box. OK, I'm paying real attention to my technique, but not being so full-on that it can be considered hypermiling.
For example, driving home from work on lates, quiet roads, if I'm doing 60MPH in 6th I can lift off the throttle entirely 3/4 a mile before J15 and still be doing 45MPH when I get there, so that wheeze alone gets me 3/4 mile free motoring.
Today I drove my 308 HDI 110 EGC 140km round trip. The first half it's slight downhill with a 9% declination for apx 4km. The return you can imagine. On the way down I got 85,6MPG but the return trip pushed it up to 65,7MPG.