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Old 07-05-2017, 06:39 AM   #1
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MPG tips

First you should NEVER use the OBC to compute your MPG. It is only ball park. ALL calculations should be done by calculations of miles driven and gallons used if you want accuracy

My OBC is always off showing high from 1MPG to a high of 4 MPG.

Now about MPG and fill ups. I fill mine to the top right below the vent holes. That way I always get a true calculation reading.

Also for accurate readings you also need to fill up at the same pump at the same time of day. The reason is different pumps even at the same station will give you different amounts of gas by volume. They are allowed a certain amount of leeway.

Also the time of day Temperatures changes the volume of gas due to expansion and even though the pumps are suppose to have the ability to calculate the temperature and adjust the volume none are perfect so the same time of day is best.

Keep your tires at max inflation.

Do not do quick starts.

Monitor your stopping distance, coast when possible.

Lastly always run pure gas if possible. It will get you 10 to 15 percent more MPG.

I have a 2015 corolla 6 speed manual rated at around 37 MPG. I have kept records of every fill-up and every mile driven and I am getting as of last fill up which is today 51.3 mpg.

There is no need to exceed the manufacturer's recommendation with octane rating. It is nothing but a waste of money as it will gain you nothing. However try to never go below it or you could suffer engine damage.

Summer gas will usually get better MPG than winter gas due to EPA requirements of what is in the gas. However that depends on Location. Also cooler temps will cause more drag on the vehicle so winter temps will lesson MPG. Rain and snow will also lower MPG due to drag.



OBC= On board computer
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Old 07-05-2017, 07:44 AM   #2
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Some added points:
  • For my last tank, my onboard computer reports about 6% better fuel economy than actual. That's quite a discrepancy.
    .
  • If you fill your tank "right below the vent holes", you risk losing fuel due to slosh as you drive away from the station. Additionally, you better plan to drive off some fuel, pronto, because it has been stored in a nice, cool, underground tank, so when it expands in your car's fuel tank, you'll lose fuel as it escapes through the vent hose.
    .
  • Fuel tanks had all sorts of weird shapes, with odd nooks and crannies. Unless always get close to empty, and you always refill at the same pump, you'll experience single-tank variances as air gets trapped in various places, rather than being filled with fuel. These get averaged out over the long run.
    .
  • The thing about cooler temperatures hurting fuel economy is that they stiffen everything up and cause much greater resistance. This includes everything from wheel bearings, to differentials, the transmission itself. Math and physics show us that drag due to variances in summer/winter air density is insignificant at normal driving speeds.
    .
  • Your driving style makes the biggest difference in fuel economy[1]. Don't overlook this one factor. My vehicle is rated at 7.4 L/100 km (highway = 31.8 US MPG = 38.2 IMP MPG), but my lifetime average of mixed city/highway driving is 6.43 L/100 km (=36.6 US MPG = 43.9 IMP MPG)
_____
[1] Assuming tires/wheels are not wildly out, mechanicals are in a good state of repair and maintenance, for similar traffic and ambient conditions, etc.
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Old 07-05-2017, 07:51 AM   #3
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Quote:
Originally Posted by SteveMak View Post
Some added points:
  • For my last tank, my onboard computer reports about 6% better fuel economy than actual. That's quite a discrepancy.
    .
  • If you fill your tank "right below the vent holes", you risk losing fuel due to slosh as you drive away from the station. Additionally, you better plan to drive off some fuel, pronto, because it has been stored in a nice, cool, underground tank, so when it expands in your car's fuel tank, you'll lose fuel as it escapes through the vent hose.
    .
  • Fuel tanks had all sorts of weird shapes, with odd nooks and crannies. Unless always get close to empty, and you always refill at the same pump, you'll experience single-tank variances as air gets trapped in various places, rather than being filled with fuel. These get averaged out over the long run.
    .
  • Your driving style makes the biggest difference in fuel economy[1]. Don't overlook this one factor. My vehicle is rated at 7.4 L/100 km (highway = 31.8 US MPG = 38.2 IMP MPG), but my lifetime average of mixed city/highway driving is 6.43 L/100 km (=36.6 US MPG = 43.9 IMP MPG)
_____
[1] Assuming tires/wheels are not wildly out, mechanicals are in a good state of repair and maintenance, for similar traffic and ambient conditions, etc.
Hello Steve. I agree that driving habits makes the biggest difference in MPG. As to how I fill I do drive about 20 miles before parking and have found no problems there. I do not agree that the gas will slosh when driving off as you claimed. There is no place for it to go with a sealed system as we have today, but thanks for taking time to mention these things.
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Old 07-05-2017, 05:26 PM   #4
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Sorry guys, overfilling the tank can lead to saturation of the charcoal canister element in the evaporative emissions system. The system is designed to collect the fumes from normal evaporation, then release the vapors into the intake manifold when the vehicle is running.

Best way to fill is to let the pump shut off do the job. While you may get some short fills, over time they will average out.

Most underground tanks supply fuel at around 65 degrees, except in extreme climates or cases where the tanks are above ground. Another example is when the fuel is delivered and the tanker truck has sat in sunshine long enough for the fuel to heat up and expand.

It definitely helps to drive 20 miles after a fill, which will prevent expansion from flooding the charcoal canister and costing a fair amount of money to replace.
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Old 07-06-2017, 02:50 AM   #5
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Originally Posted by R.I.D.E. View Post
Sorry guys, overfilling the tank can lead to saturation of the charcoal canister element in the evaporative emissions system. The system is designed to collect the fumes from normal evaporation, then release the vapors into the intake manifold when the vehicle is running.

Best way to fill is to let the pump shut off do the job. While you may get some short fills, over time they will average out.

Most underground tanks supply fuel at around 65 degrees, except in extreme climates or cases where the tanks are above ground. Another example is when the fuel is delivered and the tanker truck has sat in sunshine long enough for the fuel to heat up and expand.

It definitely helps to drive 20 miles after a fill, which will prevent expansion from flooding the charcoal canister and costing a fair amount of money to replace.
I never said I overfill. I said I fill to below the emission holes. I do this on all my vehicles one of which has over 400,000 miles and have never had a problem. It I the only way to get an accurate MPG reading.


All nozzles do not have the same exact kick off pressure and so you will not always get the same level of full on a tank by using the kick off method.
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Old 08-01-2017, 07:42 AM   #6
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You only have 4 parts of the car that actually touch the road: your tires. Keep them at least at recommended PSI, I like mine a bit above that. Just don't go crazy.
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