thanks again.

I have a hint to look for a vacuum leak also. Got this tip via youtube.

Try putting a little more air in your tyres its amazing how easier it is to push your car with harder tyres. I'm running on 40psi with my 2.5CRD and it moves with less throttle.

Yep, done that, now up to 38psi. Thank for the reply.

When you increase air pressure in the tires to above what they should be, the vehicle is more dangerous to drive.
There is less tire surface on the road, which causes reduced traction on all surfaces.

By adding a few extra psi to my tyres can you tell me how much less tread there will be on the road please as if I look at my tyres the tread is contacting 100% and that is proved by where I park on a muddy layby. I am 68 years old and been driving for 50 years so maybe my eyes don't see ball shaped tyre treads. Read years ago that the best traction in mud is too have soft tyres so maybe I should reduce my pressures when parked up. As to the dangerous handling, maybe its me that's the dangerous one when I pass about 6 cars up the back of a long lorry using a sure footed Voyager buzz bomb.

The answers to that question are listed below.
https://www.yourmechanic.com/article...flate-my-tires
https://www.quora.com/What-happens-i...o-my-car-tires
https://www.tirebuyer.com/education/...formance#close
The last one actually discusses the issue with lowering air pressure for use when offroading. I do offroading, which is uneven ground. So that lower tire pressure on uneven "soft" ground, improves traction so you are less likely to get stuck. On rocky ground, the lower tire pressure allows more of the tire tread to make contact with an obstruction in order to give the tire a better chance of climbing over it. In both of the above cases, vehicles travel much slower than highway speeds to avoid the inherent risks of driving with under inflated tires.

I used to manage a garage, and what you read in the above articles is 100% true.
And don't forget that if a tire is supposed to be inflated to 30psi, and you inflate it to 40 psi, that is a 33% increase above what the factory recommends.
That is a big increase.
That is enough to make my point.

I too go +4psi, always have done, always will. I drive on [townie] roads, my good quality tyres never get warm let alone hot.

I've dropped air to -8 only once in recent years when we had a ten day -5C, a very severe but unusual UK slick and 8" rock hard slush ridges.

75 in January and an acident and claim free record.

Just wanted to remind the contributors about the original issue:
I am having high fuel consumption problems (petrol) here, did you find the answer to your problem? Chrysler Voyager 2004 ( same as Chrysler Town and Country) Petrol 3.3l in Australia.

Things I have had checked or replaced.
*binding brakes with brake expert - no problems.
*The engine achieves normal temperature, is not running cool.
* wheel alignment
*suspension
* fitted a camber adjustment kit.
*exhaust/muffler, repaired and now all good.
*upstream and downstream O2 sensors replaced.
*Air intake temp. sensor had fault code and replaced.
*Engine coolant sensor was replaced.
*New Map Sesnor most recently.
*Taken vehicle to dealer to check for software update - finding the software is up to date.
*Had a Chrysler trained mechanic checi for error codes. none existing.
None of these replacements/repairs has made any difference to the fuel consumption.
Fuel consumption is calculated at the pump. Kilometres divided by litres. converting to 20 litres per hundred or in US galons: 12 MPG around town. 21 MPG on a highway run.

I now suspect the driving I do is very short runs, and the weight of vehicle is two tonne. Lost of stop start. I have not taken the vehicle on a highway run yet since exhaust has been repaired. The comparison may give a further insight.

Thanks for reading and your help so far.

Any petrol vehicle weighing 2.5 tons will do 15mpg/UK or less even under the best conditions. In fact most will do quite a loss less. Maybe some of the very latest such vehicles might do a little better, but it won't be by much. (E.g the BMW engined Rolls-Royce).
The remedy is go diesel (my GV averages 32.5mpg/UK, driven appropriately) or have your petrol converted to propane/LPG where in UK the prurchase price is about half that of petrol due to different taxation methods... But the cost of conversion will be around £2000. Nothing is ever simple... There are of course driving "tricks" you can use to help with mpg figures. 'Coasting' when you can is not illegal provided you don't turn off the engine at the ignition switch. I established (with a diesel engine) that 42PSI for front tyres and 35PSI were safe along with others on this site. The bulge in the front tyres were then about the same as with other radial ply tyres. Do not do a manual switch on/switch off at traffic lights hoping to save petrol -- you'll end up with a damaged battery as was found with the original stop-start idea.
Try altering your whole style of driving, the most efficient engine revs is about 2000, petrol or diesel when it comes to fuel-burning efficiency. Get used to the traffic lights in your area which all now operate on the "green-wave" principle, and drive in such a way that you never have to use the brakes in normal circumstances. Every time you use the brakes you are converting costly kinetic energy of motion into valuless energy of heat in the discs. You have to get this kinetic energy back when you set off again after braking.
AMAZINGLY, by driving slower, you seem to get there quicker. I haven't a clue why this should be so, but when you check it in depth, it does seem to pan out
Leedsman.