View Full Version : How to calculate fuel mileage v.Whats your boosted fuel mileage details?

12-31-2012, 03:46 AM
I'd like to see what kind of fuel mileage I'm geting. What is the best way to calculate this?

I'm thinking fill up the gas tank all the way. Reset the trip odometer, drive it down to about a half tank (or 1/4, or however far I want). Then return to a fuel station and refill all the way.

Subtract the amount of fuel I put in from 15.9 gallons, then divide the number of miles by the amount of fuel used. That sound about right?

It seems that she uses gas quite excessively. Of course boosting the shit out of it and staying at 3k RPM doesn't help.

12-31-2012, 04:23 AM
Lol, if you stay off the boost you'll double your mileage.

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12-31-2012, 04:25 AM
I can forsee two problems -- one is that gas station pumps are often miscalibrated. A study by Measurements Canada of 200,000 gas pumps found three quarters were shorting drivers by as much as 4.5 per cent. The other is the accuracy or lack thereof of the pressure sensor in the pump which automatically shuts the fuel off -- at the same gas station, depending upon weather conditions, I've put anywhere from five to 15 litres into the tank after the auto-shutoff kicked in.

For real accuracy, you'd need to measure out the gas in a container where you know the volumes are correct, then transfer that to the car.

01-01-2013, 12:54 AM

01-01-2013, 04:23 PM
Yeah just start logging your use with fuelly. Easiest and pretty accurate over the long term. Don't start subtracting from # of gallons...always a question if that includes neck volume, how "full" is measured, etc. Just log mileage and quantity filled. Start from a full tank.

Try to log your driving habits too over the tank. That would tell you a lot.

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01-01-2013, 04:35 PM
I think I'm around 15-16mpg right now. That's just a quick guess.

I 'filled' up (as in I was at 1/4 tank, put $30 in and it didn't auto-shut off, but did get to the F mark). I'm at a quarter tank again and I've drove like 100 - 120 miles

01-01-2013, 05:02 PM
That could be normal depending on how you drive...

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01-01-2013, 05:06 PM
The brunt of my last drive was freeway speeds (65-80) from Phoenix out to Tempe and back. Really didn't boost it a whole lot, there were a couple times where I had to let it breath out a bit.

01-01-2013, 05:12 PM
Yeah could be a bit low. Newish O2 sensor on that?

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01-01-2013, 05:16 PM
Naw. Everything is as it was. Using the stock St215 o2 sensor. I can't see my exhaust, but I have been followed by the wife and friends occasionally. They've never said anything about blowing black smoke so I don't think I'm running crazy rich and just dumping fuel. I'll pull the plugs and see how they look. If I'm running crazy rich though I'm not sure how to adjust that.....

No CEL or anything is on (I'm not sure if the CEL even works to be honest, I should trigger a fault and see if it comes on).

01-01-2013, 07:37 PM
Just keep an eye on it over a season or something.

In my MR2 Ive gotten up to 36mpg, but usually my average was around 24.

01-01-2013, 08:45 PM
Yeah the more I read and think about it, the cold weather really isn't helping my gas mileage. I just checked my tires this morning at the time I usually leave for work. They were at 25lbs of air. Now it's a few hours later I checked again, they came up to just under 30lbs of air. I think my low mileage right now is just due to the cold weather.

01-02-2013, 11:30 PM
A couple of months in with my 96 ST205 and I have to say the gas mileage isn't half bad. I have been light on the throttle with the crappy winter roads, but the cold temperatures would usually cancel that out. I expect that I can credit the taller gearing on my 205 for it's better mileage than my previous 185s.

Using the trip reset method (I always do this out of habit) I would say I have been getting just shy of 30 MPG. That's Imperial gallons, so in US gallons it would be just under 25 MPG.

Can't complain about that.

ps: stock

01-02-2013, 11:32 PM
Yeah I totally mis-calculated. I thought I only went 120 or so miles, but it was actually 170. That puts me closer to 22mpg which is what I was expecting.

01-03-2013, 04:52 AM
That sounds in line with the weather and all.

01-03-2013, 07:59 AM
My 7th gen is getting shitty mileage right now too.

Normally I can go to 420-430 miles down to "E" and fill up. Tonight I filled up at 385 miles. Kinda shitty.

The Captain
01-04-2013, 11:03 AM
Fill up with as much gas as you can put in it right to the top. Drive to at least 1/2 tank. Fill up with as much gas as you can right to the top. Divide the distance traveled by the amount of fuel dispensed (it's on the pump)

Driving Princess easy I get around 25-27. Like an ass in the mountains (hills, whatever Luni!) I get 20 dead.

01-04-2013, 12:03 PM
I just filled up. I'll see how it does. It looks like I'm around 22 right now. So I can put my foot back through the floorboards :P

01-16-2013, 02:35 AM
So quick update.

I filled up a week ago (filled it until the pump cut off, didn't top off). I'm calling that 15.9 gallons of fuel (the amount the BGB states that my tank holds). Today the dummy light came on on the way home. Stop off at the gas station and filled up again until the pump cut off (I used the same station & pump just for shits & giggles).

I put in 12.655 gallons of gas. My trip odometer was at 264 miles. That puts me at just over 20MPG of assorted driving (street and highway with a few WEEEE moments).