Drop in fuel efficiency 06 Odyessy

I have had my Odyessy maintained with a Honda dealership since purchasing it from new. Over the last month I have seen what I can get on a tank of gas drop from 520+ miles to barely 300!! I asked the dealership and they said they can do a test but it would cost $200 and take a few days. They also told me that sometimes a change in the mix my local gas station receives can effect the efficiency. (I usually fill up only at BP)

Has anyone else experienced this or does anyone have any knowledge of why this would be happening?

ps,

I keep my tires inflated to the recommended settings. And I just had a 60k service but the fuel consumption remains high.

Thanks

BC ATL

I've experienced a significant drop in mileage because of the corn juice they are polluting the dino juice with. On my motorcycle the decrease was about 10% up to 20%

yeah, ethanol has about half the energy in it that gasoline does, so they add that crap and it means you burn more gas to get down the road. also they change the gas between summer and winter. with the winter mix you get worse milage, add ethanol and the milage gets even worse.

hello! We also have this problem for past 4-5 months, everything was fine before hondo change some heat shield. Mileage drop to 270!!! from almost 400!!!