Six Gas Mileage Myths
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Very true on all 6 points. Although I still recommend keeping the air filter clean, even if it doesn't affect mileage.
I think the air filter issue is arguable: a VERY, VERY dirty one will affect fuel milage, but if you are running low rpm/ light throttle you are not flowing much CFM and there would not be much of a pressure differential.
AFA premium fuel goes, if you car is carboned up (as MANY are ) and its a High compression( >10:1)design with a K-sensor, you may benefit from higher octane to prevent timing retard. With most "economy" engines ive run the OM recommends "87 octane or higher". Given really poor e10 fuel this winter, my wifes 09 subaru got (documented) 3 mpg better with premium over multiple tanks - and I didnt even tell her to run this fuel! 27.5 v. 24.5.
AFA premium fuel goes, if you car is carboned up (as MANY are ) and its a High compression( >10:1)design with a K-sensor, you may benefit from higher octane to prevent timing retard. With most "economy" engines ive run the OM recommends "87 octane or higher". Given really poor e10 fuel this winter, my wifes 09 subaru got (documented) 3 mpg better with premium over multiple tanks - and I didnt even tell her to run this fuel! 27.5 v. 24.5.
Here are a few big myths:
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It takes more fuel to start a vehicle than it does to let it idle.
People are really confused about this one and will leave a car idling for half an hour rather than turn it off and restart. Some kids I know started an anti-idling campaign in the suburbs and are shaming parents into shutting down their cars.
Idling uses a quarter- to a half-gallon of fuel in an hour (costing you one to two cents a minute). Unless you're stalled in traffic, turn off the car when stopped for more a few minutes.
*
Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.
*
As a vehicle ages, its fuel economy decreases significantly.
Not true. As long as it's maintained, a 10- or 15-year-old car should have like-new mileage. The key thing is maintenance -- an out-of-tune car will definitely start to decline mileage-wise.
*
Replacing your air filter helps your car run efficiently.
Another outdated claim, going back to the pre-1976 carburetor days. Modern fuel-injection engines don't get economy benefits from a clean air filter.
*
After-market additives and devices can dramatically improve your fuel economy.
As readers of my story on The Blade recall, there's not much evidence that these "miracle products" do much more than drain your wallet. Both the Federal Trade Commission and Consumer Reports have weighed in on this. There are no top-secret 100-mpg add-ons out there.
*
Using premium fuel improves fuel economy.
You might as well write a check to BP if you believe this. Only use premium if your car specifies it.
**************************************************************
My take on these 6 pts:
(1)both idling and cold starts are unavoidable, there are times when stuck in traffic over a prolonged period of time where shutting off an idling engine makes good sense.
My fit typically consumes approx. 0.4~0.6L/hr of gas idling in traffic.
(2)vehicle doesn't require full warm up before you can throw it in gear and drive. I typically give it approx. 10secs during summer time (or 5) before I throw it into gear and start driving. So long as you drive gently during the 1st 5 mins or so, the engine will warm up quickly and nicely.
(3) unless you are suffering from serious compression leaks of all sorts (worn rings, valve-to-seat not sealing properly) or fuel injectors stuck in "cold" mode or have leaks, otherwise, a well-used engine fuel economy shouldn't deviate from new one by more than 5%, given all other things equal.
(4)with most sophisicated EFI engines these days which comes with all sorts of sensors, etc. to compensate the A/F ratio, unless air filter is extremely clogged, otherwise you do not need to replace air filter as frequently as, say, carb'ed engine. CArb'ed engines have very poor means of adjusting the A/F ratio as the air filter becomes restrictive over time, and thus richen the A/F ratio which lead to lower fuel economy.
(5) other than an occasional dose of PEA based FI cleaner, there's no need to play tricks to your already sophisticated engine management controlled cars for you will get no benefits from them other than lightened your wallet.
(6)with active ignition management on most OBD-II EFI cars nowadays, even high compression ratio engines can live or sometimes factory recommended the use of 87 octane fuel (computer will adjust to it accordingly) so using premium isn't gonna get you any further per tank of gas, other than the purported additional additive benefits and also lighten your wallet.
My 2c's worth.
Q.
*
It takes more fuel to start a vehicle than it does to let it idle.
People are really confused about this one and will leave a car idling for half an hour rather than turn it off and restart. Some kids I know started an anti-idling campaign in the suburbs and are shaming parents into shutting down their cars.
Idling uses a quarter- to a half-gallon of fuel in an hour (costing you one to two cents a minute). Unless you're stalled in traffic, turn off the car when stopped for more a few minutes.
*
Vehicles need to be warmed up before they're driven.
Pshaw. That is a long-outdated notion. Today's cars are fine being driven off seconds after they're started.
*
As a vehicle ages, its fuel economy decreases significantly.
Not true. As long as it's maintained, a 10- or 15-year-old car should have like-new mileage. The key thing is maintenance -- an out-of-tune car will definitely start to decline mileage-wise.
*
Replacing your air filter helps your car run efficiently.
Another outdated claim, going back to the pre-1976 carburetor days. Modern fuel-injection engines don't get economy benefits from a clean air filter.
*
After-market additives and devices can dramatically improve your fuel economy.
As readers of my story on The Blade recall, there's not much evidence that these "miracle products" do much more than drain your wallet. Both the Federal Trade Commission and Consumer Reports have weighed in on this. There are no top-secret 100-mpg add-ons out there.
*
Using premium fuel improves fuel economy.
You might as well write a check to BP if you believe this. Only use premium if your car specifies it.
**************************************************************
My take on these 6 pts:
(1)both idling and cold starts are unavoidable, there are times when stuck in traffic over a prolonged period of time where shutting off an idling engine makes good sense.
My fit typically consumes approx. 0.4~0.6L/hr of gas idling in traffic.
(2)vehicle doesn't require full warm up before you can throw it in gear and drive. I typically give it approx. 10secs during summer time (or 5) before I throw it into gear and start driving. So long as you drive gently during the 1st 5 mins or so, the engine will warm up quickly and nicely.
(3) unless you are suffering from serious compression leaks of all sorts (worn rings, valve-to-seat not sealing properly) or fuel injectors stuck in "cold" mode or have leaks, otherwise, a well-used engine fuel economy shouldn't deviate from new one by more than 5%, given all other things equal.
(4)with most sophisicated EFI engines these days which comes with all sorts of sensors, etc. to compensate the A/F ratio, unless air filter is extremely clogged, otherwise you do not need to replace air filter as frequently as, say, carb'ed engine. CArb'ed engines have very poor means of adjusting the A/F ratio as the air filter becomes restrictive over time, and thus richen the A/F ratio which lead to lower fuel economy.
(5) other than an occasional dose of PEA based FI cleaner, there's no need to play tricks to your already sophisticated engine management controlled cars for you will get no benefits from them other than lightened your wallet.
(6)with active ignition management on most OBD-II EFI cars nowadays, even high compression ratio engines can live or sometimes factory recommended the use of 87 octane fuel (computer will adjust to it accordingly) so using premium isn't gonna get you any further per tank of gas, other than the purported additional additive benefits and also lighten your wallet.
My 2c's worth.
Q.
Generally likely all true.
Myth #7: Using thinner oil will improve your fuel mileage.
Myth #7: Using thinner oil will improve your fuel mileage.
Pretty much true, though I think the idling vs. restarting thing is annoying. There are lots of other things you can do too that are also unsafe but will save you gas. Like driving 55 mph when the limit is 65 mph, or overinflating your tires. I'm all for fuel economy, but I also like to stay safe.
All true except the last, somewhat misleading, statement, which is "Using premium fuel improves fuel economy. You might as well write a check to BP if you believe this. Only use premium if your car specifies it."
Many modern cars have sophisticated knock sensors and computers that adjust ignition timing to match fuel octane. Where higher octane permits improved ignition timing, fuel efficiency may improve slightly with premium fuel. Note that this is conjecture on my part, but a reasonable one. The matter of specifying premium fuel is fading due to high fuel costs. Buyers often prefer cars that accept the use of standard fuel even if the result is a bit less power.
Many modern cars have sophisticated knock sensors and computers that adjust ignition timing to match fuel octane. Where higher octane permits improved ignition timing, fuel efficiency may improve slightly with premium fuel. Note that this is conjecture on my part, but a reasonable one. The matter of specifying premium fuel is fading due to high fuel costs. Buyers often prefer cars that accept the use of standard fuel even if the result is a bit less power.
I've actually observed that engines get better mileage as they age, as long as they are properly maintained.
It's very true those are myths.
Any improvement of mileage with premium is generally more than offset by the extra mark-up in price.
The difference is not often 20¢ a gallon.
The difference is not often 20¢ a gallon.
Originally Posted By: dwendt44
Any improvement of mileage with premium is generally more than offset by the extra mark-up in price.
The difference is not often 20¢ a gallon.
In some cases premium can keep the engine from spiraling downward out of tune. I see many cars than when the owner "floors" the throttle - the car goes nowhere billowing black carbon. They prob last floord the car 2 months prior
I just whizz past then in my tiny 1.5L.
Any improvement of mileage with premium is generally more than offset by the extra mark-up in price.
The difference is not often 20¢ a gallon.
In some cases premium can keep the engine from spiraling downward out of tune. I see many cars than when the owner "floors" the throttle - the car goes nowhere billowing black carbon. They prob last floord the car 2 months prior
I just whizz past then in my tiny 1.5L.So a dirty air filter will not affect fuel mileage? Why even change it then?
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There's a limit to the air filter thingie. The filter will have a decaying capacity for CFM. At some point this is going to simulate a higher altitude due to more inches of water column being drawn at cruise conditions producing a lower MAP output for a given TPS output. The system will attempt to balance for proper fuel trim, but I think power would be slightly reduced and economy due to the slight increase in throttling losses should become apparent.
On the warm up thing. That was all about drivability. Older cars ran like dog dirt when cold. Hasn't been an issue for decades.
The same could be said for premium. The myth stems from originally ONLY premium fuels having the right additive and cleanliness levels for the expensive Euro's that were the only injected cars in the USA. They also required premium. The REAL truth continued on in myth when everyone got injection.
HOWEVER ..to a varying degree the use of premium can produce drivability differences that can't be ignored ...so the term "will be of no benefit" isn't cast in stone. It just won't benefit you in economic or long term maintenance terms.
On the warm up thing. That was all about drivability. Older cars ran like dog dirt when cold. Hasn't been an issue for decades.
The same could be said for premium. The myth stems from originally ONLY premium fuels having the right additive and cleanliness levels for the expensive Euro's that were the only injected cars in the USA. They also required premium. The REAL truth continued on in myth when everyone got injection.
HOWEVER ..to a varying degree the use of premium can produce drivability differences that can't be ignored ...so the term "will be of no benefit" isn't cast in stone. It just won't benefit you in economic or long term maintenance terms.
Let's run the numbers on an actual not hypothetical: my wifes 09 subaru with a documented improvement running premium. 18 gallons tank used at $2.800/gal reg and $3.000/gal premium 24.5mpg v 27.5mpg respectively:
2.8/24.5 = 11.43 cents/mile regular
and
3.0/27.5 = 10.91 cents/mile premium
over 400 mile "run" this would be a $2.08 SAVINGS running premium.
This analysis indicates than untill you see at least a 2mpg IMPROVEMENT with premium you wont see any benefit to the higher expenditure - other than getting your fuel system "detergent" for free
2.8/24.5 = 11.43 cents/mile regular
and
3.0/27.5 = 10.91 cents/mile premium
over 400 mile "run" this would be a $2.08 SAVINGS running premium.
This analysis indicates than untill you see at least a 2mpg IMPROVEMENT with premium you wont see any benefit to the higher expenditure - other than getting your fuel system "detergent" for free
Originally Posted By: ARCOgraphite
Let's run the numbers on an actual not hypothetical:
...24.5mpg v 27.5mpg
How many tanks is this measured over? A 3-mpg improvement is huge but I find it hard to believe its from just switching from regular to premium.
Let's run the numbers on an actual not hypothetical:
...24.5mpg v 27.5mpg
How many tanks is this measured over? A 3-mpg improvement is huge but I find it hard to believe its from just switching from regular to premium.
Originally Posted By: TallPaul
Generally likely all true.
Myth #7: Using thinner oil will improve your fuel mileage.
i think BIG engines arent affected by this, but those with smaller engines are.
my 1.8l honda seemed to have lost a mpg just by switching to a thicker 30 weight. 10.5 to 11.5
Generally likely all true.
Myth #7: Using thinner oil will improve your fuel mileage.
i think BIG engines arent affected by this, but those with smaller engines are.
my 1.8l honda seemed to have lost a mpg just by switching to a thicker 30 weight. 10.5 to 11.5
The difference between premium and regular in my neck of the woods is $0.30/gallon.
The steps used to be $0.10 apart. I.E. 87, 89 and 91/93 were a dime apart.
Now it's $0.15 more for 89AKI and another $0.15 for 91/93 (whichever the vendor offers.) So it's $0.30 more for 91/93 compared to 87 around here.
The steps used to be $0.10 apart. I.E. 87, 89 and 91/93 were a dime apart.
Now it's $0.15 more for 89AKI and another $0.15 for 91/93 (whichever the vendor offers.) So it's $0.30 more for 91/93 compared to 87 around here.
Originally Posted By: TallPaul
Generally likely all true.
Myth #7: Using thinner oil will improve your fuel mileage.
In some instances that statement is true. Even 0.001% better mileage is an improvement. I think the benefit of fuel savings is offset by more wear.
Generally likely all true.
Myth #7: Using thinner oil will improve your fuel mileage.
In some instances that statement is true. Even 0.001% better mileage is an improvement. I think the benefit of fuel savings is offset by more wear.
Originally Posted By: Gary Allan
The same could be said for premium. The myth stems from originally ONLY premium fuels having the right additive and cleanliness levels for the expensive Euro's that were the only injected cars in the USA. They also required premium. The REAL truth continued on in myth when everyone got injection.
When I first got my new vehicle 9 years ago, I ran premium fuel even though I didn't need to. I think it was $1.30 a gallon. Now it is $3.50 a gallon.
The same could be said for premium. The myth stems from originally ONLY premium fuels having the right additive and cleanliness levels for the expensive Euro's that were the only injected cars in the USA. They also required premium. The REAL truth continued on in myth when everyone got injection.
When I first got my new vehicle 9 years ago, I ran premium fuel even though I didn't need to. I think it was $1.30 a gallon. Now it is $3.50 a gallon.
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