Fuel Economy and diff ratio

[HZSM50]

My 308 sits @3200 rpm at 110kph that's with 4 speed and a 3.36 diff. I have toyed with changing the diff and maybe go to a T5.
But now I'm just used to it, not bad I get about 300km highway driving out of the gas tank its 80 litres.
I don't do the kM you do. Its hard to compare this to modern cars economy but as I was told when my Sandman was new, fuel cost about 25 cents a litre.

[Dick61]

My 308 sits @3200 rpm at 110kph that's with 4 speed and a 3.36 diff. I have toyed with changing the diff and maybe go to a T5.
But now I'm just used to it, not bad I get about 300km highway driving out of the gas tank its 80 litres.
I don't do the kM you do. Its hard to compare this to modern cars economy but as I was told when my Sandman was new, fuel cost about 25 cents a litre.

25c a litre? must be a late Sandman!!
Petrol was about 17 to 20 cents a litre when I first got my licence in '79.
An HJ doing 17l/100km is a bit high, my Landrover Discovery does that so I put it on gas. My old HZ sedan 253/traumatic used to get around 10.5 litres per 100km on a run which was better than my 202/3spd HZ ever did.

[Beachy]

I had Holden utes back in the 80s if you want an easy way of working out the diff ratio read the rev counter at 120 kph and that will be the diff ratio I have tried it and it works I also remember playing with diff ratios didn't make much difference to fuel usage should get 500-600ks per tank or top speed .253 m20 2.78 was good to drive m21 to tall in first

[Vombil]

I had Holden utes back in the 80s if you want an easy way of working out the diff ratio read the rev counter at 120 kph and that will be the diff ratio I have tried it and it works I also remember playing with diff ratios didn't make much difference to fuel usage should get 500-600ks per tank or top speed .253 m20 2.78 was good to drive m21 to tall in first

interesting beachy. can you go into more details re knowing the diff in the car when doing 120kmph? Sweet van too! Great pick up

[Beachy]

I learnt this of a mate of mine it works for manual not sure about autos and must have 14 inch rims and standard sized tyres when I think about it ,it has to work mathematically did notice some tachometer not reading correctly through this method to