Member Since: 15 Oct 2006
Location: Surrey
Posts: 69
mileage performance/tyres correlation?
I made the following observation on a repeat journey of circa 100 miles aong the M4 at the same velocity (65-75 mph) under same conditions as far as possible (including weather-bright, light winds, air con: off, radio: on), but old versus new tyres. First journey old tyres (Pirelli scorpion 255/60 R18); computer was reset before each journey. Old tyres correctly inflated to 33 psi front/36 psi rear; average mileage for trip: 35.1 mpg. After replacement all new tyres (identical Pirelli scorpions), average mileage for identical trip 31.2 mpg. Absolutely nothing else changed, and only 1 week apart. After checking the new tyres, pressures were slightly down at 32 psi all round. Amazing effect on mileage.
Has anyone else made similar observation related to tyres?
I wonder if "improving mpg with driving has more to do with wearing tyres than engine and mechanicals?
Other details: Disco 3 tdv6 S, standard 18 inch alloy wheels, 12K miles, arctic frost, manual gearbox, sidesteps, towbar, roof bars (off), privacy glass.Don't put it off, go for it!
Are you sure the weather, outside temperature or amount of fuel in tank (i.e. weight on board) didn't have an effect on this?Matt
2nd Nov 2006 1:54 pm
suevite
Member Since: 15 Oct 2006
Location: Surrey
Posts: 69
I did think about that, winds were light, and direction travelled (ie average gradient) were the same, no hold ups to speak of. Maybe the fuel levels were different, but we are only talking ~80 kilos at maximum, which I dont think wouold bother the mass of the vehicle? I will have chance to repeat the same trip in few weeks time, any advice for data gathering considered!Don't put it off, go for it!
2nd Nov 2006 3:47 pm
Winger Site Moderator
Member Since: 15 Feb 2005
Location: UK
Posts: 3428
The onboard computer is not that accurate. 65-75mph and 35.1mpg is very good; 31.2 is far more normal. The rolling resistance of a new tyre could have an impact, but so could many other things. I suspect that if you did the test scientifically - or at least using accurate manual consumption measurement - you'd get very similar figures.
2nd Nov 2006 3:53 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26702
This week I have done @ 750 miles of mainly motorway, I have resolutely kept my speed down this week to 70-75mph, and generally driven carefully. My week average on the display is 28.3, this is compared to 28.0 actually calculated.
I don't think an auto can do much better without causing traffic jams!
I only get 22-26mpg on my auto. Yet this week I did a motorway trip and drove sensibly and didn't drive any faster than 75mph. My mpg went to 32mpg and I was amazed. I then drove locally the next day, again like a granny on a Sunday morning and I got 30mpg.
Its amazing the difference if you drive gently and slower. However, I did find it hard work driving slower than the rest of the traffic and I kept getting blocked in behind lorries. I much easier to go with the flow.Matt
2nd Nov 2006 7:24 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26702
I agree it takes some getting used to, but I did Stockport to Durham and back today, and instead of driving to be in front, and 'defending' my place on the road, I drove as submissively as I possibly could, and found it quite easy even on the manic A1.
If I can get used to this it will save me a fortune, because my average was 24mpg. I do 30k per year so thats a fair wedge, and also for the benefit of any sandal shod, bean eating, kaftan clothed, wode wearing, mead drinking, ludite thinking, environmental-extremists, I produced a bit less co2 8)
Although I think the vindaloo I had last night has more than made up for it
2nd Nov 2006 8:00 pm
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 72788
Gareth wrote:
Although I think the vindaloo I had last night has more than made up for it
Wrong gas, try CH4!
If I'm not in a hurry I set the cruise control at 60mph & get 33.5mpg.
2nd Nov 2006 9:02 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26702
How do u guys drive on m ways at less than the max the traffic will allow without falling asleep (btw i have no points on license).
LJK Setright once wrote that driving slowly is like death (or something like that). I have to agree.
M ways are for getting somewhere, time spent on them is normally not the purpose of being there.
2nd Nov 2006 10:14 pm
LeighW D3 Decade
Member Since: 31 Jan 2006
Location: Brisbane, AUS
Posts: 918
Admittedly off topic, but Gareth CH4 = Methane (the simplest hydrocarbon, also known as marsh gas but in the pure form methane is odourless) and the 4 should be subscripted but can't be displayed as such in this editor I am using. The 4 indicates that 4 molecules is the smallest stable form of it.
LeighLeighW
The old girl is on her third engine...
* first ran a bearing (design failure in original engine)
* second had a failure of the water outlet on top of the engine (pls check yours)
3rd Nov 2006 6:52 am
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 72788
LeighW wrote:
in the pure form methane is odourless
We'll let Gareth confirm whether his methane is pure!
/OT
Not picking... But the 4 in CH4 means that one carbon (C) atom has 4 hydrogen (H) atoms connected, forming the methane (CH4) molecule. The CH4 under normal environmental definition (10^5Pa, 273K) is a stable gas molecule and does not form (CH4)4 composites. Or maybe I'm wrong, it was like 19 years ago back at college
OT/TDV6 HSE Java Black, auto, difflock, fridge, winter, 7-seater, PDC, privacy, AHL, sunroof - 3rd row fixed
3rd Nov 2006 8:57 am
DSL Keeper of the wheelie bin
Member Since: 11 May 2006
Location: Off again! :-)
Posts: 72788
LeighW wrote:
The 4 indicates that 4 molecules
is the smallest stable form of it.
Leigh
Should read "The 4 indicates that 4 hydrogen atoms is the smallest stable form with the single carbon atom."
That is unless I am much mistaken. Although doing geochemistry now, I deal exclusively with silica chemistry rather than organic chem!
Yikes! Then it must be my bad English Cheers! TDV6 HSE Java Black, auto, difflock, fridge, winter, 7-seater, PDC, privacy, AHL, sunroof - 3rd row fixed
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Maybe the fuel levels were different, but we are only talking ~80 kilos at maximum, which I dont think wouold bother the mass of the vehicle? I will have chance to repeat the same trip in few weeks time, any advice for data gathering considered!
