Happywanderer wrote:

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Been to my tyre man. He has pumped tyres up to 40. He said not wise to go up to 45 as when they get hot after driving a while they can go up another 10 which would put them up to 55. Better at 40 going up to 50 when hot he said.
He also said the tyres and wheels are the right size.

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 There is a generally recognised mechanism for ensuring that your tyres are at the right pressure and it is known as "The 4 psi Rule".

Using a good quality pressure gauge, sheck the tyre's pressure when it is cold. Then drive for at least 30 minutes and re-check the pressure. The tyre pressure should have gone up by 4 psi.  If it has gone up by more then the tyre has been getting too hot and the starting pressure was too low. If it doesn't increase by the 4psi then the starting pressure was too high.

Obviously, the pressures you need for travelling around town and being fully loaded and travelling at speed on the highway will be different so it is a matter of working this out for each different type of driving you do. 

The only variable to this rule is for Light Truck tyres where an increase of up to 6psi is acceptable as their heavier construction will generate, or at least tolerate, more heat. 

My brother had a van similar to Myrtle, it was a Ford Econovan, and he ended up running his at 34psi around town and changing that to be 40psi in the front tyres and 42psi in the rear tyres for his loaded up runs down the freeway. You might consider using those pressures as starting points for your tests if you choose to bother.

I do get rather "anal" about tyre pressures though and I have a compressor mounted under the driver's seat (with a long hose) to allow me to re-inflate tyres whenever I drop the pressures, and I do drop them for different road surfaces all the time.

For instance, I will normally drop them to 22psi if I am driving on sand, or 18psi if I am towing the van down the beach, and I have gone as low as 12psi for really soft sand.

Similarly, I will drop them down to 26psi if I am driving down a gravel road littered with gibbers. It is important to reduce speed as well of course, to keep the heat build up as low as possible. 

Enjoy the drive to Geelong - I used to live there and I still have some very fond memories of the place. 

The previous estimation was 16.78 litres per 100 ks


or 5.96 ks per litre


Easier than going looking back a page for the figures.

Happywanderer wrote:

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How can that be so different to the firast calculation and so much better.

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Just a couple of things come to mind HW..

Difference in terrain, difference in weather conditions, winds, tyres pumped up more and your driving style.....you were consciously making and effort to drive more efficiently......makes a lot of difference.

Was Myrtle as heavily laden with water, camp gear, food clothes etc??

Happywanderer wrote:

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Could be the reaaon Boroma. All of those. I didn't bother filling the water tank as staying at my sisters.

The load would be similiar to last trip, may have slight difference in weight. Actually a bit more as I brought down my sewing machine for sister to play around with.

I did go the same way for the first 50ks as prefer the country roads. Then it was 90 all the way except through the towns.

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 You did not have water in the tanks but you did take the sewing machine.....how do they compare??  Remember for every litre of water you have it is a kilo in weight.....20 litres water = 20 kilos weight.

Did you still have your outside furniture packed in Myrtle??

And you may well have traveled the same route but weather conditions also contribute to fuel usage....hot, cold, winds etc

Slowing down, braking and then having to build speed again are all considerations too as is traffic....more this time less next time etc.