Trip:
BC 99 from Vancouver, BC to the U.S. border, then I-5, I-505, I-80, I-280 a little past San Francisco, CA
Stops on average about once an hour, for fueling the machine and/or the driver and phone conversations
Speeds between 60 and 90 mph, around 70 most of the time, not using cruise control

Fuel:
Various 87 (RON+MON)/2 octane U.S. gasolines: Chevron, Shell, 76

Car:
A late 2006 automatic/GT RX-8 with 4K miles on the odometer [5K after the trip]
Fresh 5W20 VV174 Valvoline oil
Stock 18" wheels
Stock Dunlop SP Sport 8090 at 36 psi
Wing spoiler
Dual-muffler exhaust

 

Segment 1:
http://maps.google.com/maps?f=d&hl=e...=UTF8&z=8&om=1

I always leave Canada with a near-empty tank [if you've seen their gas prices, you know why], so the very first thing after the border is a fillup near Bellingham, WA at 08:27.
Next fillup is Vancouver, WA at 12:35.

Average speed is 256 mi/248 min=61.9 mph=99.6 km/h.
Fuel consumption is 256 mi/9.722 gal=26.3 mpg=8.94 l/100 km.

 

Segment 2:
http://maps.google.com/maps?f=d&hl=e...&cd=1&z=8&om=1

Normally, I prefer not to buy fuel in Oregon because all stations are full service, but by the time I got to southern Oregon, I figured I shouldn't take chances with the long climb to the Siskiyou Summit ahead. I stopped in the last large town of Medford, OR, around 17:15 [the receipt does not show the time]. In retrospect, I had enough gas to safely make it to Yreka, CA, so RX-8 is quite capable of crossing all of Oregon, and then some, on I-5 without refueling.

Fuel consumption is 287 mi/10.735 gal=26.7 mpg=8.81 l/100 km.

 

Segment 3:
http://maps.google.com/maps?f=d&hl=e...32617&z=8&om=1

Last stop to fill up is Vacaville, CA at 22:21.

Average speed with stops since Vancouver, WA is 598 mi/586 min=61.2 mph=98.5 km/h.

Fuel consumption since Medford, OR is 311 mi/12.332 gal=25.2 mpg=9.33 l/100 km.

 

Summary:
It took from 08:27 to 22:21, or 834 minutes to cover 256+287+311=854 miles, making average speed with stops 854 mi/834 min=61.4 mph=98.8 km/h.

Average fuel consumption is 854 mi/32.789 gal=26.05 mpg=9.03 l/100 km.

Fuel cost is $93.16/854 miles=$0.109/mile=$.068/km.

 

Good data, and I see that you aren't seriously complaining about 26.0 miles to the gallon..................just stating that it's higher than you thought possible? Be happy!

 

Maz, I think you may be reading that wrong. His avg MPG looks to bee about 9 miles per gallon.

Correction: I read it wrong

 

floyd re -read

 

no... 9 liters/ 100 km.

26mpg.

and that is not that abnormal. i have a 6mt, and i've sen 24.5mpg on 50 miles of highway, and 10 miles of city. but i stuck to 65mph (cruise control) the entire, grueling time.

 

Ahhh...its is what I get for posting before morning coffee

 

Remember CA reformulates its gas in October through March for emissions, and gas mileage typically drops a couple MPG when that happens.

 

Phew.............I thought I picked the wrong week to quit sniffin' glue!

 

See what happens when you use CA gas. There's something odd about CA gas formulation that seems to drop MPG.

 

Exactly, that was my first thought when I realized I am getting through all of Washington (280 miles) on less than 2/3 of a tank.

All gas accounted above was Washington and Oregon gas, so I can't blame California reformulated gas for the slight drop in gas mileage toward the end of the trip. But you are right, now that MTBE has been banned for being the carcinogen that they knew it was, California gas contains E-85 ethanol that is harmless to us but can't be good for the engine or the gas mileage.

Or the price of torillas in Mexico: http://news.bbc.co.uk/2/hi/americas/6319093.stm

 

haha that's funny, California reformulates their gas for emissions but get less MPG in the end.

 

well some of the OR gas near the boarder is the CA spec stuff too.

Yeah, they Oxinate the gas in Fall/Winter, so it burns cleaner, but it also reduces the BTU that you can extract, so you end up using more gas to get the same power and distance.

And MTBE only got banned because it leaks out of all the gas storage tanks and into the ground.

 

26 mpg is great... i wish...

 

ha ha ... abnormally good mileage! I think the best I've ever done on a highway trip is ~23mpg. Kudos!

 

I wasn't aware that automatics could do so well. I must be the worst manual driver ever because it seems the best I can do is about 20-21 mpg.

 

^^
Need to understand he was cruising down I5.. Its ALL highway.. Very nice stretch. Done it several times.. Nice post!

 

There is nothing normal about this car. My observations with my Scan Gauge II have shown me that. I expected high gas consumption and heat as your turn more revs. Nope. Seemed to cool the best and get the best overall gas mileage at 4-4.5K RPM cruise. At 75, I pulled back into 5th for a cruise. Very little change in economy. In fact better if you are on uneven road. RPM over Load equals better economy. Even dropping back to 4th at 75 did not produce the heat and fuel consumption you would expect. So far I get 20mpg at average speed of 20 something. At 75 in 6th yields 25 on even grade. Not sure what average speed of 60 would actually do. Another thing, you would thing that coasting would cool down the water temps. Nope 4k RPM does. Water pump can't circulate water when you coast. Take more RPM over lugging it.

 

6-speed Sport mode AT 12.9L/100Km 8.6L/100Km
6-Speed Manual 12.8L/100Km 9.2L/100Km
4-speed Sport mode AT 12.9L/100Km 8.8L/100Km

Good mileage but the autos should always get better mileage. My best remains 10.0 l/100km @ 118 km/h for 480km of highway