fuel economy on 225/75-16" tyres

Hi Guys,

I've been running my mud terrain 225/75-16 for the last two fuel fills and the fuel economy is suprising.

For those of you who don't know I live on a mountain and drive 70kms each way to/from work. 1/3 of my trip is across the mountain and down the winding road down 500m TVD then across the flat plains in 80kmh zones with about 15kms of motorway. There are at leat 6 points where I come to a complete stop and make a hard-and-fast right turn into a flow of trafic traveling at 90km/h. Return journey is the same with 1/3rd being up the mountain which I usually hammer as hard as the guy infront will allow.
Previously I've been averaging 9.9L/100kms over a full tank of 98 octane on my typical 140km daily route to work and back (top peak speed 100km/h) and it only rises to 10.8L/100 if I use an alternate longer route which is the same distance down the mountain the opposite direction then a longer distance all on the motorway (top speed 120km/h) which is near on 180km but still has the same mountain height to ascend alebit via a different but equally as steep road.

After fitting the wider rims and bigger tyres I've noticed some unusual things:

* I can easily pull up my street which is very steep in 2nd where as I had to push 1st out a lot harder before it would hold in 2nd

* my fuel economy is 9.7L/100 on my non-motor way route and 10.1L/100 on my motorway route including more right foot as I've used a fire trail to avoid slow trucks a few times. These calculations includes the +5% distance added to my odometer which I have confirmed with my GPS and knowing exactly how far my route is door to door.

I was expecting the larger diameter would sap my fuel more on the stop-start sections than give back to me on the open road and honnestly i'm finding I still stick to the spedo limit which is +5% now so i am probably driving a tad faster. This combined  with the agressive tread and noise should give me worse fuel economy - I mean I MUST be burning at least 1L of petrol / 100kms just to generate the wicked noise these tyres make on the freeway, let alone the extra rolling size!

Maybe the 2L engine simply likes to operate at 500rpm lower and gives me more torque there? who knows..

Thanks