Good question. I was thinking the same thing today.
I'm going to syphon the tank down to a couple of gallons anyway, to save the weight. Also, I may just avoid filling the tank again until its empty - I'll just top up from the syphoned stuff as needed, and use it up. So maybe i'll fill in December-ish?
On the way home though, I pulled off a 76.8. It is a 5.32 mile trip according to Google Earth. The SG only reported 5.1. Looks like I need to do some tweaking.
IMO, a handheld GPS is the only reliable way to calibrate the scanguage, by verifying the speed, and therefore the distance travelled.
(Of course, the two are inter-related, and to calibrate my unit, I just went for a long trip (in kms) with Scanguage at zero, and then adjusted to make up the differnce... using the distance of the GPS trip versus the Scanguage trip... I found that to be better than going by speed alone.)
2005 smart cdi, 799 cc 3-cyl common rail turbo diesel
My weekly fillup came a little early. I took my car to the track to see what it could do, plus I did some WOT tuning to prepare, so the mpg from this tank dropped a bit. 34.5mpg may sound low, but it's still far above what other DSM's get. It's odd, I feel disappointed that I only got 34.5mpg, while other DSM owners have never gotten that many mpg on their best tank. So I guess I'm doing OK.
Last tank 10.1 gal/365.5mile/36.13 mpg
This tank 10.2gal/365.9mile/35.85mpg
My next take will be higher(if i do the same driving). I pumped all the tires to 50psi. and am puting my front belly pan back on. I also added some acetone (I know, but it might help clean the injectors).
2008 EPA adjusted:
Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
Hey DRW, I am impressed with you gas milage. Getting nearly 40mpg and still being able to run under a 14sec 1/4mile.
Thanks! I'm impressed, too. I was hoping to go faster at the track, but 44 psi in the front tires isn't the best way to take off from a start. I was tempted to add a few gallons of 100 octane unleaded and drop the tire pressure to 25, but I wanted to keep the car in exactly the same configuration as I drive it on the street.
I went up against a turbo Civic on my last run. He pulled a 14.1 @ 102mph, so I'm not the only one with a large HP/FE ratio.
Today was both good and not so good. I started out this morning with temps around 28F. The trip to my wife's work came in at only 29.3 mpg. From there to my work was 47.1. On the trip to my wife's work, I don't FAS to let the engine warm up; I do nICE when I would normally FAS . I noticed that when I was coasting in neutral that the engine was running abnormally fast; sometimes at nearly 2800 rpm's. I've heard from other Saturn owners that this is not an uncommon thing with lots of FAS . At lunch time I went up to the gas station and refilled. While I was refilling, I disconnected the battery so I could re-set the ECU's keep alive memory. When I re-started, I didn't FAS on the way back to work, just nICE. The car idled at just over it's normal idle speed of ~900 rpm's while coasting. I forgot to mention that the idle speed would drop to normal if I sat at a complete stop for long enough. This afternoon on the way back to my wife's work I did only nICE and I was able to pull off 51.2 MPG . From there back to my house I got 51.5 MPG . The temp was 36F. I think what I'll do for this tank or at least part of it anyway, is do only nICE and see how the tank FE goes. After that I will try adding some FAS and keep an eye on the idle speed. Another thing that alerted me to a possible problem was that the ECU was running in open loop most of the time when I was doing my pulsing. This is yet another benefit to having a Scanguage.
Horsepower is how hard you hit the wall, torque is how much of the wall you take with you.
612 miles 11.7 hours of driving two top off fillings Newport to Maine and Back in just under 13 hours total time and man did I suck some gas down 65-75 mph cool temps and cross and head winds and the TOLLS ARG!!!!
Oh yeah and the road surface in NH was really noisy and as I crossed into MA it got really quiet and my MPG jumped up at least 5 mpg I swear!! I would see 32mpg at 70mph then draft a truck or SUV and it would go up to 40mpg - crossing into MA it went up to 39mpg at 55-60mph no drafting - speed really kills mileage in this box! I miss my Geo where I could cruize at 70 and still get 50mpg!!! The GPS shows a lot more mileage than the SG or the Odometer. Return trip 1 GPS track 326 miles, SG showed 312 miles, Odometer 303 miles and roughly 37.5mpg for the entire high speed trip.