General: V70 fuel tank size question

[Nick44]

As opposed to Red Diesel, or agricultural diesel.
In the UK (don't know about anywhere else) there are 2 types of diesel.
Exactly the same stuff except that red diesel has a dye in it that makes it red in colour, and had very little excise duty, and diesel for excised vehilces (cars and trucks, buses etc) as Jim says Road Vehicles>
DERV.

[TheJoyOfSix]

Originally Posted by Nick44

Slightly off-topic, but I hope of interest.
My 2008 MY V70 D5 has an entirly untrustworthy MPG computer, and a speedo that has proved to read 3 MPH under correct value.
To my mind I have proved this by passing "your speed is" signs, and cross referencing with my Sat Nav.
Always the external speed measuring devices indicate that I am doing 3 MPH less than the car speedo does.
My Dealer -sort of- acknoledges that Volvo speedo's often do not match up with Sat Nav devices, but insists that Volvo are right, but with God knows how many £Billion worth of satellites up there, and my Sat Nav can usually see 6 of them, who is likley to be right? A probably (sorry Volvo) 50p chip, or a billion dollar satellite?

Begs the question, if the car really is going 3 MPH les than indicated, and as the Odo gets it's information from from the same source, how many miles have I actually done?
And therefore, what is my true MPG, and how many times have overrun a service that was needed, and how does the mileage figure on my lease really work?
As Jim said, working out MPG (over a few tanks) is not hard, but if you can't trust the Odometer your calculations will always be wrong.
And with Derv at £1.40+ a litre that can make quite a difference!
Bet Jim isn't paying that for Derv!

My S80's speedo reads 4mph faster than gps says, but if you set the cruise control at any given speed and then reset the 'average speed' function on the trip computer the readout given corresponds with the gps reading.

This makes me think that the car does accurately know the distance travelled but that the speedo is set to display a higher figure for safety purposes.

Bear in mind that the test should be carried out on a level road as gps will read low on a hill as it measures horizontal distance not actual distance.

[ASt85]

You may find that there is a significant difference between the mileage covered according to your odometer and that actually covered - depending upon tyres/rims fitted to your V70, there may well be up to a 10% margin of error in the miles covered for a given volume of fuel - the same odometer is used on a number of models and there is a proportional difference in the actual circumference of the wheels/tyres fitted. If you have a sat nav look at the speed indicated by your speedometer and that indicated by the sat nav. My V70 indicates 77 mph when the sat nav indicates 70mph, confirmed by motorway mile markers and an old fashioned stopwatch! So, if you apply a correction factor, 10% in my case, you arrive at the true mpg or miles per litre.................crickey my V70's actually done 17,500 fewer miles than the odometer indicates.
It is worth checking, 10% is a significant error, and is comparable with the margin of error used by our esteemed constabularies when a range of speed CAMERAS/radars/”gatsoes”/guns & etc. are used to determine speed/velocity. Most V70’s apparently are a little optimistic about the true speed and hence the mileage, since they use the same sensor(s) to make the guestimate!
So, as stated in an earlier post, go by how much fuel is needed to refill a previously full tank, and use the distance covered from a sat nav – margin of distance error of the sat nav is of the order of a few hundred metres in a long journey.

[Andy]

Doesn't a satnav calculate mileage along a flat map and in reality the odometer is also measuring the curvature of the earth hence the difference in the two figures???

Just throwing it out there as I'm sure I'd heard it somewhere!

[ASt85]

If the distance is relatively short ie less than 5 nautical miles//5.75miles on the "flat" the difference between the "straight" distance ie level distance traversed and that of the true distance covered ie over the curvature of the earth will have less significance than the margin of error in the odometer.....I think that makes sense[/I]

[Jim314]

Originally Posted by ASt85

You may find that there is a significant difference between the mileage covered according to your odometer and that actually covered - depending upon tyres/rims fitted to your V70 . . .

The different wheel/tyre combinations that Volvo prescribes for the V70 all have very close to the same diameter at the tread. There is no Volvo approved wheel/tyre combination which would give a rolling diameter different by 10 %.

Nominal diameter at tread for Volvo approved wheel/tyre combinations for the V70

195/65-15 is 25.0 inch
205/55-16 is 24.9 inch
215/55-16 is 25.3 inch
225/45-17 is 25.0 inch
225/40-18 is 25.1 inch
235/45-18 is 25.4 inch

[ASt85]

Take your point it, does not seem like a big difference in diameter, making a maximum difference on one rotation of the wheel around 1.57inches, so, if we take the median circumference as 79.0213 inches that would account for an inaccuracy of +/-1.99% between the largest and smallest diameters (around +/- 34 yards in one mile)- OK not a huge error, but it would explain around a 4% margin on indicated speed and distance, so if you then go +/- one scale division of the speedometer at 70 mph we get to around 9% error, factor in the curvature of the earth over longer journeys and we might well be getting to around 10% error. Makes you think doesn't it!

[Jim314]

Originally Posted by Jim314

[snip]
Nominal diameter at tread for Volvo approved wheel/tyre combinations for the V70

195/65-15 is 25.0 inch
205/55-16 is 24.9 inch
215/55-16 is 25.3 inch
225/45-17 is 25.0 inch
225/40-18 is 25.1 inch
235/40-18 is 25.4 inch

Correction of tyre profile for 18" wheels.

[R-P]

Originally Posted by Nick44

As opposed to Red Diesel, or agricultural diesel.
In the UK (don't know about anywhere else) there are 2 types of diesel.
Exactly the same stuff except that red diesel has a dye in it that makes it red in colour, and had very little excise duty, and diesel for excised vehilces (cars and trucks, buses etc) as Jim says Road Vehicles>
DERV.

Same here (Holland).
Supposedly a friend of a friend had his 150 liter watertank in his landrover full of red-diesel and hooked up to his engine.
His normal tank had regular (3x more expensive) diesel in it in case he ever got stopped by the police...

I've never heard anyone being stopped who had his diesel tested by the cops though, nor would I know where to buy red diesel.

And I've put 70.63 liters into my 68 (AWD) fueltank. Click to see my mpg stat in the sig. My speedometer is some 6% off though, and my mpg indication is off as well (actually l/100km indication).

110 on the speedo is actually about 103-104 (km/h, not mph on the GPS, they start writing tickets above 105, so that's why I know this one quite well, don't go over 110 on 100 roads and I'm safe. As for the new 130km/h speed (implemented this year), it guzzles too much (hardly 30mpg...), so that I never drive anyway).
7.72 (36.6mpg) average fuelconsumption according to my Volvo is actually 7.53 (37.5mpg) according to the fuel-stat-site (~2.5% off)