I see your point and I have heard it b4 whlkev, why buy a $50K car and try to save a few bucks at the pump, but mt point is that, if 89 does not make any difference, then why buy 93.

the answer would be 93 COULD BE ok, maybe in cold weather. but if it's warm and under certain condition, the engine could ping. and i won't risk that.

I wish I was near Riverside and wanted a farm. My GS460 consistently gets 19mpg in town and 25+ on the highway according to the onboard computer.

I've never had an AWD of any kind, but that's got to account for the low mileage.

17 mpg on a stock v6!!!!! OUCH. Whats the temp like?. I do know that when ambient temps drop below 45-50 deg F you will lose mpg secondary to increased air density and added fuel by the motor. if you live in MD it probably freezing right now. I live in AZ and have noticed a slight drop in mpg even with 45 deg temps at night. Im sure everything is ok. wait until spring and I think you will see it go up.

this is interesting concept to me about cold air. i thought with cold air (higher density) you get more power from the engine thus effectively you don't need as much gas (to achieve the same level of power)?

maybe after it drops below certain threshold things get worse again? for sure at warm (hot) temperature car is not as powerful

Wow...I think there are some people that need to do a little research on gas. The higher the octane the less "Volatile" the fuel is. The lower the octane the more explosive. The reason you should not use lower octane is because gas will actually explode without a spark if the pressure is high enough. That is how a diesel runs. E85 is like 106 octane. The only reason you cant use it, is because it is corrosive because of the alcohol in it. I was a comptroller for a oil company and most of the time the octane is actually higher than what is posted. If you don't get any knocking then go for it!!!

Here's a solution that may help people who WANT to use High Octane...but don't want to pay the extra $$... Check out Sunoco on a Friday ... at least here in TN...all of the Sunoco stations have Premium for the price of Mid-Grade on Fridays. Check out your local Sunoco...and try to time your fill-ups.

BTW....I do NOT work for Sunoco!

with my 07 awd, im getting 16mpg
n i always fill it up with 92.

I average between 22-24 mpg in mixed driving.

Anyone here find the on board MPG computer 1 or 2 MPG higher than it actually is?

I haven't actually checked the on board computer by keeping track and assumed what it said was what i was getting. After reading this thread, thinking it's worth some arithmetic.

I did the manual calculation vs the MPG computer on my last 2 Lexus and they both have been 1 to 2 MPG higher on the computer.

Looking at what I think is the obvious reason for the lower MPG's, is the inefficient nature of the AWD system. There is probably some effect on MPG's using lower octane fuel but probably not as much as the AWD itself. Just my .02

On a high compression engine such as the 350, you should notice HP and MPG lost using 87 octane, I am just try to figure out if anyone here have notice it.