Do you own a G500? Please read...
Hi fellow Wood and Carpet Brigade (Power Division) members
Just a question for you all. next time your out, can you take a note of your MPG? I was reaching between 16.6-18MPG, but recently have dropped to 13.5-15 MPG. Have had a major service, new spark plugs etc etc but still not really affecting the MPG - which is strange. (I used to find that after a service it would hover around the 18MPG mark for the first few 1,000 miles.
I have changed my tyres, and expected to see a drop,but not to what it is today. Typical motorways speeds 60-80 mph town, staying to legal speed limits. I do notice that the cooling fan does come on more frequently, so was wondering of it may be some of the Salisbury plain mud left over from the summer...?
Any ideas or thoughts would be appreciated ( however we can leave the get a smaller G out of this! :) )
many thanks
Spider1V
Might be worth asking the people who serviced it if they adjusted the mixture.
Does the power seem the same?
Running a bit hot wouldn't necessarily mean lower mpg.
If a bit low on power it could be injector seals (cheap) - they harden over time. I've done it on my 230 - pretty easy job.
More random thoughts as and when.
Hi Spider,
I get around 15.5 mpg in my 500 (SWB) driving around up here in the Highlands. Local roads mostly quiet A roads with some single track and I usually drive at around the posted limit (ie 60 most of the time). It doesn't seem to vary much unless I do a longer run, say to Edinburgh, when it improves to about 16.5.
What tyres have you changed from/to? In the past I've found that ATs, for example, tend to be worse on fuel than normal road tyres.
Does seem odd that a recent service coincides with your increased consumption. Are there any other symptoms - eg is it accelerating as well as ever?
Sorry not much help ......
I have a 3 litre straight six in my G and never get more than 14mpg. Spider has a 5 litre V8 and normally gets 18mpg.
That just does'nt seem fair.
I get 19/20 mpg from my swb ge300 but it is manual and this has been consistent over the last 7 years or so..
Unless you have had the front grill off and removed the air con rad to clean the main rad, then it is almost certainly still partly blocked after Salisbury plain, the fans need power from somewhere, and they ain't solar powered, ;-). Bound to have a small effect on MPG.
It is virtually impoosible to thoroughly clean the rad without removing the air con rad. There too close.
Check the difference in wheel diameter between your original tyres and the new ones, link here.
I think you told me that you did have the computer reset for the new size? If not the MPG display will be slightly out, but either way I'm convinced larger tyres use more fuel, even the slightest increase in tyre diameter puts the gearing out of whack, and an AT tread will use slightly more again.
Buy some nice lightweight shoes and stop resting your foot on the floor. ;-)
I think they go nice with the wood and carpet.
Jo theres the answer in the setence above mate,
It's those tyres you changed (we were discussing the other day), I found that as well when I had AT's they are bulkier and the other type you had before were normal type of tyres if you know what I mean.
Joe,
Just did a run on the motorway and also reset the trip computer after a few local road trips.
At the first the motorway was showing 22.1mpg - but after the entire journey, I was down to 17.something. I wasn't pushing it but was near the speed limit (give or take 10mph) and was 'enjoying' myself.
Local trips, with a little bit of a heavy foot, seem to give circa 15 mpg.
I'm sure I could scrape more out of it but the 500 is a little too much fun to be sensible in!
I expect it’s the tyres.
Partly due to the additional drag but mostly due to the additional circumference messing up the trip computer. Can’t be bothered with the maths but you are actually travelling further for each rotation so it’s not actually as bad as you think.
I’ve noticed my trip computer does this when I’ve changed tyres.
Russ
If it is the tyres then bear in mind that you probably have 20% more weight there now and, once that weight is moving at a reasonable speed the engine has to try a bit harder to speed them up - think gyroscopes and engine governers.
However you did say the mpg changed after the service, not after the tyre change so I'd still like to eliminate a bad setting on the injection system or fuel pressure.
High fuel pressure could be a sign of a failing pump.
Ahhhhhh the pleasure of having too many variables as my maths teacher used to say:-)
I have had a few PM's saying it could be the new tyres, one advice is to add an extra 10% air into them and see if that affects the MPG - Will try that tomorrow. The G500 I have has a SatNav that you can input the new tyre dimensions and on my random journies I tend to check them and make sure they are both in sync, and they tend to be .......
The tyres are much wider than the last lot I have, so, as people have commented (Mr DentSmithy) that maybe the sheer wieght of the tyres has such a large effect....
That will soon change....
Spider1V
Probably a combination of a few things, fans running a lot and bigger tyres.
MPG for G280 PUR and G280PUR with "offroad package", ok, the off road package may have a few things that reduces MPG slightly, but theres a huge difference in MPG, I would say thats mainly down to tyre size, the difference in tyre size between these G280's is probabley double the increase of your new tyres, but it give you an idea.
Could just be that your spare tyre is considerably bigger since xmas Joe try reducing that one by 10%
Not wanting to state the obvious but have you checked the tyre pressures?
It is an obvious one but if they aren't correct, this could effect the mpg.
Do you know? That was funny...... You should be on the stage!
Prefferable the first one out of town...
the 'lithe' Spider1V :P
Hi Spider,
I've got my (LWB) on the same tyres that you have and alternate them with a set of slightly higher diameter MTs in the Winter. Basically fuel consumption does go up BUT MARGINALLY (compared to the smaller 'stock' tyres). With a Roof rack and loaded up I get between 15-18 mpg on a run (last one through Germany, on the motorway - proabably a steady 80mph/130kmph or so). I found that I was getting about the same, but perhaps only a little better, with the smaller tyres and before all the mods were done.
Regarding the computer, have you checked your indicated speed against your actual/REAL speed? I use my Tomtom to measure my REAL mileage as the speedo is about 5-7% out. According to the tyres (yours are about 6-8% larger diameter than the standard ones) and the speedo reading (cars are apparently allowed to show a discrepancy from the REAL speed by up to 7% in order to be homologated - as long as they show a FASTER than REAL speed), this could easily 'fool' your car computer into falsely giving you a 11-15% inaccurate mpg calculations. I think there could be reasonable doubt that the dealer has managed to correctly 'adjust' the car computer's systems/readings for the new tyres.
I'm afraid there is only one thing for it: drive a known distance from a petrol station having just filled up at a particular pump and refil it from the same pump - how much fuel have you used and what was the distance?............I've found that the extra diameter tyres DO drain a little more mpg in the city (more torque required) but improve on the motorway (less rpm). Having a '99 model year, I do not have the on-board electronics to do my calculations for me: I have always done them using the tomtom mileage versus how much fuel I use between fill-ups. The fact is that in the 500 it is hardly noticable as you've got so much power/torque under your right foot the engine is not straining to grapple with the extra oomph required to turn the larger tyres. I think, if you try the admitedly somewhat geeky approach as described, you'll probably find that there isn't much in it before and after.
.....and finally tonight.....
If you are still not won over, my wife has a 2008-super-high-tech-benz whose 'comand control system' does just about everything. However, having shod it with slightly smaller diameter winter tyres, all the readings are out. The dealership insists it 'made adustments', I confronted them with my 'most-precise' calculations, pre and post, which stated they had NOT managed to do what they said they could do........long story short: I keep my own records of mpg/distances travelled, I have given up trying to explain to the MB dealership why they are wrong and I sleep well at night in the knowledge that the REAL figures have stayed within my personally acceptable tollerance bands.
Hope that helps,
Phileas
don't over inflate your tyres as this will lead to excess wear in the centres. Try deleting the spare wheel and carry a couple of cannisters of tyre repair foam.
Hi Paul
the reason behind the suggestion to over inflate the tyres was to lower the footprint for a thirty mile run in an attempt to determine if the new tyres were causing the the higher fuel burn ---not to drive on them them over a long period
Thanks you all for your tips and advice. I check the tyres and they were in deed a little flat, I have left them at just under the upper limit (acording to the natty little guide I have on my filler cap) and we are back up to the 17's for MPG - much happier now!
Spider1V
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No front grill off - yet.
New fans (were replaced after the 'Sainsbury's face lift' the G had back in July.
With regard to the tyres 285/60/R18 is what I have now and they replaced the 265/60/R18 I had before. (any higher and I would not be able to get into the local Waitrose car park...... which would mean Clare would want me to sell the car!!!!
Perplexing
Spider1V
P.s On the slipper front - sorry more of a Totes man myself.