Chilly, thanks for your thoughts. I agree with your points 1-2. For 3, I am surprised that the EPA estimates are based on 55mph. Are the new ratings rules that are coming out changing the mph ?
Don R's point about octane rating and high ambient temperatures makes sense to me. I have always used the middle grade of gasoline in my BMWs and I guess I will have to do the same with the hybrid. I am not so overly concerned about the cost of the fuel, I can well afford it. I was just somewhat surprised at my resultant mileage.
From a tire inflation standpoint, I have always religiously used the values that the manufacturer specifies since I have had performance oriented cars and their suspensions and handling design points are based on the inflation they publish. I keep my tires at 32psi cold which could be close to 40 psi when temp is over 100 and car is rolling at 80mph. So, I don't guess I will mess with that variable. BTW, I run my truck tires at 65-70 psi.
The speed limit in Arizona is 75, crossing over into Calif it goes to 70. You might find me going more than 5 mph over in the boring stretches of desert on Interstate 8.

 

Here is a link the EPA test schedule. If you click on highway you will see they never go above 60 mph. The high speed, AC, and Cold Temp, test were just added recently and up until now, they were not include as part of the EPA estimate.

http://www.fueleconomy.gov/feg/fe_test_schedules.shtml

Also note that the average highway speed is only 48 mph. at 80 mph over a long stretch of highway, the EPA estimates don't even come close to representing your driving conditions.

 

I've been running 87 octane for a few weeks and the mileage has gone down. I'm going to run 91 of 93 this week and see if it makes much of a change.

 

I see the oil price peaked at 78.77 today for a new all time record. I wonder how long until the 4$/gallon would be a better calculation for the 87 octane vs. the 4.10$ for a 91 octane premium?

 

Based on what everyone else has been saying (and now that I have a number of tanks in to give me a relatively stable baseline on my expected MPG at 87 octane), I decided to try a tank of the mid-grade 89 octane. Didn't do anything different, driving wise.

Net result, based on my one tank experiment? 33.26 MPG, a full 1.5 MPG more than the previous best tank that I had with the 87 octane, and 4.03 MPG over the average MPG of all previous tanks.

Obviously I'll need to run some more tests to verify, but if I can average an additional 50 miles per tank, then that should justify the extra $1.70 (at most) it will cost to run with the mid-grade stuff. It will be interesting to see if 91 octane would give me an extra 100 miles per tank for the extra $3.40 (at most) it would cost.

 

Don R.

After about 2,000 mi, looks like 87 oct is giving me 28-29 mpg and 93 oct is giving me 30 - 31 mpg.

From what I've read, a engine with a CR of 11 can use up to about 95 octane and still extract maximum efficiency (31 or 32% v. 30%). Have you tried 94 or 95 octane (mixing Sunoco 100 octane - race fuel available at some stations - with 93). It would be interesting to see what your Scan Gauge shows for timing advance at steady-state cruise. With Sunoco 100 selling at $6/gal, very doubtful this is cost effective, but might be possible to get 32 or 33 mpg.

 

There are no longer any Sunoco stations in the Chicago area as far as I know.

For another easy gas mileage boost, switch to 5W-20 oil from 5W-30 if you already aren't using it. It takes about a half hour of engine running to fully warm up the oil. The oil warms up slower than the coolant. Cold oil is a significant drag and the hybrid operation tends to keep the oil temperature low during city/suburban driving.

 

Will keep the tip in mind for next oil change, as we are in the 90's now in the Pgh area. Just performed my break-in oil and filter change and am trying Mobil 1.

For a list of Sunoco 260 GT100 Locations, check this site
http://www.sunocoinc.com/Site/Consum...GT100Locations

Doesn't look like anything in Chicagoland.
(Note: This list is not entirely current, so call ahead).

The location that I am going to try - Beaverun MotorSports Complex http://www.beaverun.com/ - is off PA Tpke exit 13 and fortunately is on my way to work (:

 

Using 0W-20 after my 5,000 mi oil change. Noticing significant effects of lower resistance. Under optimal conditions (30-40 mph P&G, some downhill). I'm seeing 37 - 41 mpg over a 40 mi leg. It's eerie now to see average digitial mpg rise as I'm driving up slight upgrade - where it had decreased slightly before.