Surprise increase in mpg

[chefdave]

Hi yesterday had to do a 280 mile round trip to inverness from john o groats. Most of the roads are 2 lane roads over scottish mountains with lots of twists turns steep climbs and descents. Then city driving. Average mpg is 40 imperial mpg. This was in a pugeuot 406 estate with 2.0 engine and auto box. Gov figures are max of 39 mpg at 56 mph under ideal conditions. Mods done are increase tyre pressure by 4psi front air dam and partial grill block. Not bad considering air temp was 4c or lower. Still need to get engine under tray tweeked and sort back bumper/parachute sorted so have portenial to get even more.

[MetroMPG]

Congrats!

It's not often you read comments about surprise increases in fuel economy at this time of year!!

Not bad considering air temp was 4c or lower.

Not bad at all.

[cRiPpLe_rOoStEr]

I see more people reporting an MPG increase (often accompanied by a discrete performance improvement) when there is a higher amount of moisture in the air.

[chefdave]

Cripple rooster that makes sense but on day i did drive it was sunny. Which confused me. In my car you can feel a difference if it is very cold ie below freezing. Only thing i can think of is that i managed to optiomal load/vaccum for engine revs by luck not judgement or I let engine do what it wanted with little input from me. Defferently need to put some throught in to it. Will be doing same run in new year so see what happens then.

[jakobnev]

You get better mileage when you do longer trips.

[chefdave]

Jakobnev that is true but my 40 mile round daily commute is over similar roads. Have done the same trip many times and never got such a high figure usually get 37 mpg which is good. The 280 mile trip included a drive across city in rush hour. Lots of roundabouts and red traffic lights not the best for mpg. Trips before have always avoided rush hour traffic. Thinking back i did solve a very very tiny water leak by thermostat had to do the housing bolts up by 1/2 a turn. Maybe its the extra couple of temperture degrees. Engine runs at 80c on temperture gauge. Still a bit low for a 85c-87c thermostat. As stated before air temp was 4c dropping to 0c on highest parts of route. One mountain climb and drop is full of tight turns and very steep where you cannot get out of 2nd gear for 3/4 mile and have to keep power on to climb. A flat motorway would be a better guage for mpg.

[cRiPpLe_rOoStEr]

Originally Posted by chefdave

Cripple rooster that makes sense but on day i did drive it was sunny. Which confused me.

Moisture in the air doesn't need to involve rain. Just go to a coastal city and you're likely to figure it out quite easily. But anyway, an MPG increase in a rainy day is real, but it might become ineffective during to an increase in traffic volume.

[chefdave]

Cripple rooster 80% my driving is on the coast. No more than a mile from coast. If google maps and put in john o groats to inverness you will find road follows coast and crosses 3 estuarys. The other drive i do is to thurso and follow north scottish coast. Maybe it was a high humidty day with no rain. So many variables on how i got increase. See what happens on next trip.

[cRiPpLe_rOoStEr]

Originally Posted by chefdave

Maybe it was a high humidty day with no rain.

Which is not unusual at all in a coastal area

[WelshAdam]

Well done mate! Similar sort of conditions that I'm driving in at the moment (South Wales mountains, freezing or just above, 2.0 litre Mondeo Estate). I struggle to get 45mpg in these conditions so fair play to you.

Adam.