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YOUR RESEARCH2007 Boxster 987 3.4s manual - poor fuel consumption. - Page 2 - Boxster/Cayman - PistonHeads UK
Leading reported evidence
Check maf sensor is
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Read evidence and context
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Performed · outcome unconfirmed
I presume you have a newish air filter in place and have checked the maf sensor is clean.
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Performed · outcome unconfirmed · Original poster
CEL hasn't been on, but I did have the AOS changed before I bought it, so its possible the MAF is oiled up.
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Suggestion · Original poster
Thought cleaning of them was generally ineffective.
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Suggestion
You did reset the trip before starting for accurate results didn't you?
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andygo said:
Top down on the motorway, cruise on,70mph, but only getting 22mpg. Seems a bit low? I"m a new owner, but thought I'd get better than that!
Sounds dire - to the point where something is wrong - unless you were driving into a hurricane.
I'll take a better sample over the weekend, but its a bit alarming given that I'm off to France in a few weeks on a 2500 mile multi venue jaunt....
On the plus side, its a lovely car, goes like stink.
Sounds about right to me.
My 07 3.4 averaged 20mpg on a recent trip to Spain and France but to be fair I did cain the arse out of it at every opportunity.
I got back from a 2500 mile Eurotrip in my 2008 3.4 a couple of weeks ago and averaged 22.4mpg. I had the top down the whole way and think I was probably averaging 24-25 on the motorways and a lot less on the fun roads!
anonymous said:
[redacted]
I'd agree.
I know hardly a direct comparison but my 986S tends to show around 27 for a roof down motorway cruise (around 25 with faster jaunts) and have averaged 36 with the roof down and a steady 70mph cruise.
For comparison. Just been touring on the continent in 981 S Cayman (PDK - so high gearing in 7th helps). Mostly motorway stuff, and above 70 - averaged 35 overall. Only one real chance to cruise at 3 figures on German Autobahn - got an astonishing (I thought) 33mpg, but it was one way so may have been wind assisted. I'd expect around 38mpg at 70. I also did brim to brim checks and the figures the computer gave were pretty much spot on.
I don't trust the mpg display on mine at all.
The other day, I reset it and drove about 10 miles in town traffic before I got on the M25. When I got onto the motorway it read 19mpg, when I got off 25 miles later it was on 21.
On the way back, I reset it as I got on the motorway and did the same route, again cruising at exactly 70mph through the camera zone. This time 35mpg.
Unless my maths is wrong, 10 miles at 19mpg and 25 miles at 35mpg should average out at over 30mpg, not 21.
I realise that this is not a scientific test, but it is a long way out. The other thing that annoys me is that it doesn't change at all after a while. I don't use it all that often, and I went through 2 tanks of petrol with it stuck on 24.6mpg regardless of how I was driving.
I have a 981 Boxster S with PDK. Got back this week from 1800 mile French trip, averaged just over 39mpg. Admittedly mainly main roads and sticking fairly closely to the speed limits. The use of the glide facility aids consumption a lot. You can glide for a mile or two on some downhill sections. Nothing special about my car; give it the beans on a back road and it's in to the low twenties. Oh, that consumption is 95% hood down. Had to put it up for torrential rain for half an hour and when it hit 34 degrees one day and threatened to burn my wife and I to a crisp.
I have a 981 Boxster S with PDK. Got back this week from 1800 mile French trip, averaged just over 39mpg. Admittedly mainly main roads and sticking fairly closely to the speed limits. The use of the glide facility aids consumption a lot. You can glide for a mile or two on some downhill sections. Nothing special about my car; give it the beans on a back road and it's in to the low twenties. Oh, that consumption is 95% hood down. Had to put it up for torrential rain for half an hour and when it hit 34 degrees one day and threatened to burn my wife and I to a crisp.
OldChap said:
I have a 981 Boxster S with PDK. Got back this week from 1800 mile French trip, averaged just over 39mpg. Admittedly mainly main roads and sticking fairly closely to the speed limits. The use of the glide facility aids consumption a lot. You can glide for a mile or two on some downhill sections. Nothing special about my car; give it the beans on a back road and it's in to the low twenties. Oh, that consumption is 95% hood down. Had to put it up for torrential rain for half an hour and when it hit 34 degrees one day and threatened to burn my wife and I to a crisp.
As you say the glide function does seem very effective. All that said and accepting that the 981 pdk is going to be significantly better than a 987 manual, 22 does seem very poor. I haven't seen figures for the extra aerodynamic drag on a Boxster with the the hood down - but I would guess at somewhere around 20% mark, perhaps a bit more. The increase in fuel consumption would be less than that because at modest speeds friction and tyre drag are still significant. So I'm still surprised if there isn't something wrong with the car - even if it's only an inaccurate fuel computer.
Run back from Revolution in Brighouse today, combination of motorway, A roads and traffic jams saw an average of 35 indicated on my 987.1S.
So 22 on a motorway does seem to be very, very bad.
Been really pootling about today,- A roads, b roads, driving very sedately with the odd squirt of beans. 19.5 mpg. Somethings not right, but wonder what it could be?
Seems excessive. On a recent roadtrip to Cornwall (from Kent coast) my 3.2S Averaged 32.9 mpg for the whole trip. Had the roof down for the entire week aside from about 20 miles (840 miles total)
Doesn't sound completely terrible, but it does seem a little on the low side:
My 987.1 2007 3.4S normally does around 25-26 mpg on the motorway on cruise (with the roof up), obviously quite a bit worse around town or being driven hard. A 2005 987.1 3.2S I know well does a little better. My old 2003 986.2 3.2S would do 31-32 on motorways on cruise with the roof up which I think is just due to smaller wheels / tyres (18s vs 19s), more camber, slightly less toe, lower rolling resistance tyres (Michelin PS2 vs Falkens) and a slightly smaller shape and lower drag coef.
Assume you have checked the tyre pressures and the tyres aren't scrubbing and wearing hard on any edge / corner of the car?
andygo said:
Been really pootling about today,- A roads, b roads, driving very sedately with the odd squirt of beans. 19.5 mpg. Somethings not right, but wonder what it could be?
I presume you have a newish air filter in place and have checked the maf sensor is clean.
Not checked the MAF sensor, but air filter has only done about 7k. CEL hasn't been on, but I did have the AOS changed before I bought it, so its possible the MAF is oiled up. Thought cleaning of them was generally ineffective.
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