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Old 05-07-2008, 01:11 AM   #33 (permalink)
MPG Centurion
Join Date: Apr 2008
Location: Houston, TX
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New Tip

Found one that isn't on the list!

Always fill up at the same station - And no, it's not a numbers game. Has to do with the fuel trim tables in most cars (visible through SGIIx). When you change brands of gas it can cause your trim tables to go through a bit of re-programming. This can have a small (or large) hit on MPG. The idea is to reduce the variance in the fuel going through your engine as much as possible. Using the same brand gets you most of the way there, but filling at the same station cinches the deal. Certain metro areas (like Houston) require special blends of gas. If someone was to fill up at a shell in Bryan, TX they would get totally different gas than filling up at a shell in Houston. Sticking to the same station (and same pump if your wacky) reduces the probability of variance in your fuel mixture as much as possible, hence mitigating the reprogramming of trim tables to a minimum. As a side note I'd say that high dollar brand names are more consistent than bargain gas. One other bonus with using the same station is that you might actually get lucky and hit the same batch in two consecutive tanks. The station has huge underground tanks. If you fill on Monday and Friday (pick any two days) you might actually catch them before they get their next shipment of gas. Also when they add a batch, that change is blended throughout the whole station's reservoir, reducing the change per gallon. On the "numbers game" side, using the same pump will reduce the variance from tank to tank since each pump is calibrated independently.

I've been doing this since November and it has a HUGE impact on my Ford. Not so much on my Toyota. I'd say changing stations reduces my tank numbers by 15% no the Mercury. Takes about 3 tanks for the trim tables to settle down and ease back in to the consistent 30+ range.

If I can only give 3 tips to someone it's:
1) Tire maintenance (air, rotation, balance, align). <= On the list.
2) Drive your car like you'd ride a bike. <= On the list.
3) Always fill from the same brand, station, and pump.

Originally Posted by thebrad View Post
I know I'm probably an exception here, but I generally fill up at the cheapest place in town (Costco) and now that prices are on the rise they are generally subject to 15 minute or more lines. Anyway, I shut off the engine and wait for all cars in front of me to fill up and then I push my car up to the spot and proceed to fill.
Nice... Try finding the station that is consistently cheapest (or in the bottom 3). Pick a pump there and commit to filling your next 5 tanks there. Make sure to try this the month AFTER they switch to the Summer gas. You should see an improvement and save money over the long haul.

Originally Posted by Doofus McFancypants View Post
I had not thought about backing into spots. Sometimes when i get to work later than usual, the good Pull out spots are taken and i had wondered what the best alternate was. Now i know - back into a spot with a warm engine to allow pull out with a cold engine.
I've never interpreted "face-out parking" as backing into a slot if it means you need to burn gas to do it. What you do is find a slot on a hill. Then you coast (engine off) up the hill just past (10 feet) the slot. Then like a pendulum, you'll stop and start rolling back. Cut the wheel and your face-out parked on the top of a hill. Perfect. Only really makes sense if you can do it while in an engine-off coast using the kinetic energy you already have invested in your mass (car).

PS... Absolutely fantastic list Don't change a thing... Well other than my suggestion and the "printable version" thing

Houston Hybrid and Hypermilers Club <>

Best commute = 14.3mi @ 114 MPG (sg2)
Best (non-trivial) tank = 759mi @ 80.7 MPG (fcd)
MPG Centurion-Hybridfest 2007-Prius II-26mi @ 106 MPG (sg2)
Dan <11011011>
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