mio

Hi guys,

I dunno if it is just me... my car used to run 380- 400km per tank,

but after 30000KM, it can only run 330km - 350km per tank... do u guys know the reason why???


Thanks you!

PS: my car sometimes jerks when 3rd gear at 1800rpm, around 50km/h, is there something wrong with the engine? or clutch?

subinf

driving habits/location changed? Added a roof rack?

mio

no...

adonis_xu

tire presure maybe

mbwmn

has the weather been colder up at the SecretBase?

SouthernBoy

Your "PS" note.. can you clarify this? Give a little better description? When you say jerks, do you mean a surging or tendency to studder?

Sounds like you might need to make use of a high quality fuel system cleaner, such as Chevron Techron.

jdb8805

MT? If the clutch is slipping, it could cost you fuel mileage.

SouthernBoy

He states that he either has 30,000,000 miles or 30,000 kilometers (I will go with the 30,000 kilometers since if it is the other, I suspect a serious typo).

Anyway, at 30,000 miles (or kilometers), if he's got a clutch going out, either he has a VERY faulty clutch or he has been doing something VERY wrong.. unless he's racing the car.

Under normal conditions with a properly installed and designed clutch, there is no way you are going to get under 100,000, or better yet 150,000 miles out of a clutch unless you are operating it entirely wrong.

From his initial description, I suspect fuel system contamination, but there is just not enough information to indicate a good diagnosis.

derrickmosley

Ever heard of oxygenated gas?

gt1

mio thinks in metric, so my guess that he is Canadian, which means cold winters. Gas mileage is always worse when it is cold for a varitey of reasons.

bluenoise

I agree with this guess. I have been averaging about 25-27 MPG during the cold weather, but we had nice weather last week and I averaged about 29 on that tank, all else being as equal as can be.

SouthernBoy

It's not a guess.. it's a fact with modern cars. The reason is this.

Colder air is more dense, which means more oxygen molecules per cubic foot. An automobile engine operates most efficiently when it can maintain an air/fuel ratio of between 14.7 and 15 to 1. When there is more oxygen in the intake charge, the ECU will read this through the oxygen sensor and compensate by increasing the fuel delivered by the injectors to offset the oxygen-rich condition. Timing will also be advanced. This is great for us enthusiats who lust for more power and response, but it comes at a cost with lower fuel economy.

The reverse happens in warm weather conditions, which is why you will get better gas mileage in the summer.

bluenoise

Cool. I figured that was the explanation (the computer trying to keep the fuel/air ratio consistent with varying air density), but I misread the post I was quoting. I thought he said he guessed why that was the case. He actually was guessing the poster was Canadian.

Thanks for the details to back my assumption, though. I was just trying to explain this to my dad yesterday and now I have a better way to put it.

SouthernBoy

Interestingly, the reverse of all of this was the norm before the advent of ECU-controlled EFI systems.. in other words, carburetors and demand fuel delivery.

With a carburetor, there is little that can be done when there is a change from summer to winter months, unless you are of a mind to rejet the thing for these season changes.

In the summer months for cars of the 60's, for example, because the air was less dense and more humid (humidity (moisture) occupies space and does not advance combustion), the mixture entering the cylinders was leaner. So in order to accelerate from stops and even drive in a normal fashion, slight increases were needed to the throttle to attain and maintain speed. This would result in more fuel being burned because more throttle means more opening of butterfly valves in the carburetor(s), which equates to more fuel being drawn into the cylinders.

In the colder months, with the air more dense and oxygen-rich, each cylinder fill received more oxygen and therefore, a better burning of the fuel and more power. So in the winter, you would tend to get better fuel economy than in the summer.. provided your right foot did not take advantage of the extra winter power.

Incidently, oxygen sensors do not sense oxygen.. they sense heat in the exhaust stream. An engine with too much oxygen and not enough fuel in the mix (say a 17:1 ratio), will burn lean and therefore create more heat. Same with too much spark advance. Conversely, if the mixture is too rich or if the timing is too retarded, the burn is cooler. This is how the ECU knows to adjust the fuel delivery and timing to get the most out of the ambient conditions.

SouthernBoy

You're absoltely correct. Years ago, when I lived in Arlington, VA and had my '88 Mustang LX 320CID, I ran some tests. Fuels in the close-in counties of Virginia (as in Northern Virginia) used to be oxygenated between November 1st and, I think, the end of the following February. So I recorded fuel mileage just before and then after these fuels starting being sold. I found a 14% reduction in fuel economy with the oxygenated fuel, but with the side affect of a very noticable increase in power.

A_UFO

Nope. What is oxygenated gas and how do I know if the service station is using oxygenated gas?

triggle

Mio is talking of a 10% decrease in economy. Canadian winters are milder than you may think. Temps here are way up from a few years back. I find it a stretch to say that air density and oxygenation is the cause. On top of that I think he's on coast and the weather here in Vancouver has been very mild this winter.

I've also experienced a lower average economy as it was 10l/100 in winter now it is 11l/100 winter, but I think I can attribute this to less (unnecessary) highway driving as the gas prices have gone beserk.

rjheard

I've had good success with Lucas Fuel System Treatment.

Actuary

mio lives in warm BC. I don't think cold weather is affecting him. Maybe it's winter gas, tire pressure Mio

1gokart

At least you're not averaging 19 mpg. Weather is cold up here in Michigan, I guess my TL likes to drink a lot when it's cold.

SouthernBoy

Mine is still averaging in the 25 MPG range, though for the most part, we've had a relatively warm winter here in this part of Virginia. However, February has been below average (average being 46 degrees F for February).

SouthernBoy

Oh, that's 25 MPG for in town driving, not highway.

A_UFO

Oxygenated Gasoline (not classified as reformulated gasoline outside of California, Arizona or Nevada): Finished motor gasoline that contains an oxygenate. This type of finished gasoline is primarily used during the winter months in regions of the United States that are not in compliance with carbon monoxide standards. Other areas may mandate the use of oxygenates during a portion of the year to help control other types of air pollutants. Oxygenates can also be mandated for use to achieve compliance with minimum use goals.

• EPA Winter Oxygenated Gasoline: A finished gasoline that contains a minimum of 1.8% oxygen by weight. This type of finished gasoline is mandated for use during the winter months in areas of the United States (other than California, Arizona and Nevada) that are not in compliance with federal carbon monoxide standards.
• Arizona Winter Gasoline: A finished gasoline that contains ethanol at a concentration of 10% by volume. This type of finished gasoline is mandated for use during the winter months (November through March) in certain areas of Arizona. Prior to blending with ethanol, the unfinished base gasoline is referred to as Arizona Blendstock for Oxygenate Blending (AZBOB).
• Nevada Winter Gasoline: A finished gasoline that contains ethanol at a concentration of 10% by volume. This type of finished gasoline is mandated for use during the winter months (October through March) in Clark County. Prior to blending with ethanol, the unfinished base gasoline is referred to as Nevada Blendstock for Oxygenate Blending in Las Vegas (LVBOB).

Oxygenates: Alcohols and ethers which, when added to gasoline, increase the amount of oxygen in that gasoline blend. Common ethers in use as oxygenates include ETBE, MTBE and TAME. A common alcohol in use as an oxygenate is fuel ethanol.

• ETBE (Ethyl Tertiary Butyl Ether): An oxygenate blendstock, formed by the catalytic etherification of isobutylene with ethanol, intended for gasoline blending.
• MTBE (Methyl Tertiary Butyl Ether): An oxygenate blendstock, formed by the catalytic etherification of isobutylene with methanol, intended for gasoline blending.
• TAME (Tertiary Amyl Methyl Ether): An oxygenate blendstock, formed by the catalytic etherification of isoamylene with methanol, intended for gasoline blending.
• Fuel Ethanol (Ethyl Alcohol): An anhydrous denatured aliphatic alcohol intended for gasoline blending.

Reformulated gasoline:

Finished motor gasoline formulated for use in motor vehicles, the composition and properties of which meet the requirements of the reformulated gasoline regulations as stated by the U.S Environmental Protection Agency under Section 211(k) of the Clean Air Act. Most RFG uses methyl tertiary-butyl ether (MTBE) as an oxygenate. There are three types:

Standard Reformulated Gasoline

Since January 1995, this gas has been mandated in areas where toxins in the air are a constant problem. It also contains oxygen-rich chemicals but in lesser concentrations than the winter-oxygenated gas. It also is designed to reduce certain toxic chemicals found in conventional and winter-oxygenated fuels. It's termed Federal Phase I fuel and was replaced in 1999 by Federal Phase II.

Oxygenated Reformulated Gasoline

A wintertime fuel exclusive to the New York City area where heavy carbon monoxide pollution occurs. In the summer, regular reformulated gas is used.

California Phase 2 Reformulated Gasoline

This gasoline, introduced in June 1996, has a different formulation and burns cleaner than regular reformulated gas. In March 1999, Governor Gray Davis issued Executive Order D-5-99 ordering that the MTBE in California RFG be phased out, with none of the oxygenate in the fuel by December 31, 2002. This was because of concerns over MTBE contaminating ground water supplies.

Winter-Oxygenated Gasoline:

Introduced in 1992, this fuel is sold where carbon monoxide from car exhaust is a problem. It's a conventional fuel with oxygen-rich chemicals added, such as MTBE (methyl tertiary-butyl ether) or ethanol, grain alcohol. The oxygen promotes cleaner burning, reducing carbon monoxide. In areas where oxygenated fuel is mandated, this gas is generally sold from November to March because cold engines run less cleanly and produce more carbon monoxide. In summer, conventional gasoline is used in most of these areas.

Ka0tik

i get 225 miles per tank, is that bad?

bTwix

I know, I'm getting 13-17mpg avg. with just CAI and custom magnaflow exhaust. Could be a clogged air filter, remote start, tire pressure, etc.

Here's interesting link. It's for bikes but should still be largely applicable.
http://faq.f650.com/FAQs/Poor_Mileage_FAQ.htm.

SouthernBoy

Good Lord, you people are getting some terrible mileage. Even when my car was new, right from the start, it never got below 22 MPG for in-town driving. And within the first week of ownership (in July of '04), it was up to 24 MPG back and forth to work for in-town driving.