How many miles in a tank?

[dirtydog]

i usually run till at least the light comes on! I cant see the problem when my fuel filter is changed every 10k (kms) but i am switching to 5k now as they are cheap enough and due to the veg.

for reference i can measure mine against the GPS and 20mph indicated is almost 30mph! by time i get to 70mph its spot on

[Pauleds]

Best you be careful through 30mph speed cameras then Dirtydog......

[The Kid]

Circumference is calculated as:

Diameter x Pi (3.145927)

So,

for a 31 in tyre it's 31 x 3.1415927 = 97.389373 in

for a 33 in tyre it's 33 x 3.1415927 = 103.6725 in

How the h**l you work out relative speeds and mpg from that is beyond me!

As far as mileage goes, my 3.0L Manual turbo, based on records kept since Aug 04, has done 16973km on 1745ltr of diesel i.e. 9.72km/ltr or 27.47mpg.

The most I've put in the tank is 49ltrs and the most kms was 488

[Medieval Dave]

This is what I don't get - people are getting figures from 14 to 27mpg.

I think more people need to keep a log of liters fuel used against miles travelled across several fillups and then we can work this out

[CaptainBeaky]

Circumference is calculated as:

Diameter x Pi (3.145927)

So,

for a 31 in tyre it's 31 x 3.1415927 = 97.389373 in

for a 33 in tyre it's 33 x 3.1415927 = 103.6725 in

How the h**l you work out relative speeds and mpg from that is beyond me!

As far as mileage goes, my 3.0L Manual turbo, based on records kept since Aug 04, has done 16973km on 1745ltr of diesel i.e. 9.72km/ltr or 27.47mpg.

The most I've put in the tank is 49ltrs and the most kms was 488

Elementary, my dear Watson...

When a 31" tyre rotates once, the vehicle moves forward a distance equal to the circumference of the tyre - ie 97.389373 in.

When a 33" tyre rotates once, the vehicle moves forward a distance equal to the circumference of the tyre - ie 103.6725 in.

Hence for every rotation, the 33" tyre will move the vehicle 1.0645 times as far

ie a + 6.45% error.

The speed will show exactly the same error.



Ergo, if Surfstar's odo IS reading in km, his 340km should actually be 361km, and that STILL gives c r a p fuel consumption.

OTOH, if his odo reads in miles, with the same error, that gives 360 miles to a tank, or approx 28mpg, which is respectable.

So, Surfstar - does your speedo go up to 100mph or 160 mph?

BTW, I average approx 24-25 mpg, KZN185 on standard tyres.

Regards

[mark g8awo]

TRy this web page and download the fuel Calculator it works in all formats

http://www.drivearchive.co.uk/index.htm


This way you get an average of what your rig is doing to the gallon between fill ups

[pkdj2307]

2.4 ssr-x 1992 J

I can honestly say i thought my surf was thirsty until i saw your figures, around town and driving quite hard i get about 22 mpg but on a long run i have got as much as 30 mpg and thats loaded, driving to cornwall at around 80 mph. when i top it up 130 kms costs about a tenner usually.

[MattF]

This is what I don't get - people are getting figures from 14 to 27mpg.

One of lifes little mysteries.

I think more people need to keep a log of liters fuel used against miles travelled across several fillups and then we can work this out

The problem appears to be working on the basis of a 'tank full'.
It would appear there may be more variations in tank sizes than
first thought?


Matt

[Koi]

Two tank sizes as previously said.
My pick up with 36" tyres on is well out on the speedo readings.
At 30 on the clock I am doing 36 and at 60 on the clock its doing 72 checked with a sat nav, faster you go greater margin of error.
On my 2.4 Surf I used to fill up, reset the trip do 300 miles and fill up again my 3.0 Runner is the same. I have had the runner down to 240 miles for a tank but that was long motorway drive and country roads at high speed cruising.
All depends on driving style and sort of journey covered, you have to remember its 2 ton in weight and if you drive it like a sports car with right foot flat to the floor all the time its gonna drink the juice.

[The Lovely Boyo]

I have a standard 2.4 with recon engine and turbo, it does 330kms maximum on a full tank, i simply dont believe the claims of 500 odd kms on a tank.
I'm sure my tank is smaller than 57litres.
Is there a fuel light which comes on when you get really low? most i have ever put in is about £40 worth of diesel. and the guage was really low.
If there is a fuel light i might run it till that comes on and see what i get but i dont fancy running out as i dont know how to start a diesel once it's run out.

Hello,

I have had my surf for 3 years and done over 50,000 miles, so I've got a good idea of the milages I get.

If I'm towing the horses around in the summer I'm lucky to get 18 - 20 mpg.
Normal everyday driving I get about about 24 mpg.
If I drive to Scotland (from South Wales, done it several times, 2 adults 2 kids lots of camping stuff) I have got as much as 515 km's from 54 litres (the amount I almost always put in, usually just before the red light comes on) = 27ish.

My driving is rarely over 65mph (and no I have no points, so I'm not protecting my license!).

Fuel consumption will be seriously affected over about 60 mph - wind resistance becomes a major issue (which partly explains why lorries have never been made very aerodynamic, there is little advantage below 60 mph, and why fast cars are).

Gotta say this thread has been one major debate !!!!

[cr15]

Two tank sizes as previously said.
My pick up with 36" tyres on is well out on the speedo readings.
At 30 on the clock I am doing 36 and at 60 on the clock its doing 72 checked with a sat nav, faster you go greater margin of error.
On my 2.4 Surf I used to fill up, reset the trip do 300 miles and fill up again my 3.0 Runner is the same. I have had the runner down to 240 miles for a tank but that was long motorway drive and country roads at high speed cruising.
All depends on driving style and sort of journey covered, you have to remember its 2 ton in weight and if you drive it like a sports car with right foot flat to the floor all the time its gonna drink the juice.

Er, check your math again. The error is constant at 20%.

[NiftyNev]

Er, check your math again. The error is constant at 20%.

His math looks ok to me. You are correct in saying the error is a constant 20% but the difference in actual speed and the speedo reading increases.

If doing 30 by the speedo and you were in a 30 zone then you would be booked for being 6 over. However if you were in a 60 zone and doing 60 by the speedo you would be booked for being 12 over. Makes a difference in the hip pocket..

Nev

[Medieval Dave]

It's exactly what you would expect though. if you have 36 tyres, and you assume the speedo was set up for 31 then the error is

100* New tyre diameter / origional tyre diameter

0r 100 * 36 / 31 = 116.2

thats a 16.2 % error.

or if the pickup was origionaly on 30's then it's

100*36/30
= 120
exactly a 20% error

So if I put some mini wheels on my surf i will have excellent acceleration, never set done for speeding, and the wife won't complain about the step up anymore.

[Tallyman]

And the "Ground Effect" from being that close to the tarmac would give you great traction and the wife wouldn't need to climb up to get in.

[The Lovely Boyo]

It's exactly what you would expect though. if you have 36 tyres, and you assume the speedo was set up for 31 then the error is

100* New tyre diameter / origional tyre diameter

0r 100 * 36 / 31 = 116.2

thats a 16.2 % error.

or if the pickup was origionaly on 30's then it's

100*36/30
= 120
exactly a 20% error

So if I put some mini wheels on my surf i will have excellent acceleration, never set done for speeding, and the wife won't complain about the step up anymore.

Ha ha,

A surf with 10'' mini rims - now that I gotta see, please do it and send us all a photo - I need a laugh, given that I've got to get my tax return in this month (yuck).

Would it be ground effect or would you just be sitting on the diffs?