Fuel Economy Drop-Off

[dedwards0323]

I know this topic has been discussed before, but my search of The Forum didn't really give me any 'heads-up' on my problem.

Since we purchased our 2006 NB Conv back in April, we've consistently gotten 20-22 MPG around town. That fuel economy has been pleasing since the drop top is so much fun to drive! But the last 2-3 fill-ups has only yielded 17-18 MPG. Quite a sudden change!

I've checked the scanner and there are no fault messages of any kind. I'll probably start by checking the air filter since the car is approaching 60k and I'll bet the air filter is the factory original. If so, it's probably way overdue for a new one. A dirty & clogged air filter will make the car run rich, causing poor gas mileage. And I firmly believe to start with the simple stuff first before tackling bigger tasks. Although changing the air filter doesn't appear all that simple either, considering all the stuff surrounding the air box.

I'm not planning on tackling the fuel filter because I suspect it would be detected with difficulties in starting due to restricted fuel flow. I don't see any signs of this right now.

Anyone else ever have this reduced MPG all of a sudden show up? And if so, any pointers on what you did to correct it?

Thanks,

[Smileybug]

Has it had a tune-up at all? Spark plugs, etc? On the fuel filter, I had mine replaced earlier this year, and it was the original filter at 11 years and 90k. No problems starting the car or anything but my MPGs were not so great. Replaced it and I had a much more responsive car when I hit the gas pedal. I'm getting 23-25mpg around town now.

[FreqWiz]

Did your gas station change the amount of ethanol in the gas for the winter?? That can cause the drop in MPG for the winter.

[MyOtherRidesAVette]

10+% drop all of a sudden? Betting it's a little more than dirty filters or a change in gas mixture. I'd bet more on a bad plug, plug wire, or a sensor gone bad. Sure that NBM will come on here and help out.

However, check your manual for all the things that should have been replaced or serviced by now, tune-up being one of them (at 40K), assume none of them have been done, and get to it...

[miffmole]

Ethanol can cause up to a 10% decrease in MPG. It's happened with my car...which makes ethanol "enhanced" gasoline totally useless.

[MyOtherRidesAVette]

Originally Posted by miffmole

Ethanol can cause up to a 10% decrease in MPG. It's happened with my car...which makes ethanol "enhanced" gasoline totally useless.

Oh, quite to the contrary, it greatly enhances the BIG oil companies' profits! All in the name of GREEN !

[FreqWiz]

One other benefit of 10% ethanol is that it keeps your injectors cleaned. If you run 10% ethanol you do not need to run injector cleaner, because the ethanol will clean your injectors.

[MyOtherRidesAVette]

Didn't know that! Learned something else today! Thanks! I think though the cost of the additive would not be offset by the 2-3 mpg lost. Do the numbers! Probably going pay attention to what I buy and run non-ethanol for a while and see what it does to my mpg.

[FreqWiz]

Well I think it is funny to watch people pay $5 for injector cleaner and then put 10% ethanol in the car. that is a waist of $$$$$$$

[MyOtherRidesAVette]

but, I was out in Cedar Park (west Austin) the other day, out by Lakeline Mall, and got gas at an H.E.B. Never saw it before, but they had a "pay to add" (big $$$$), injector cleaner additive, that would be added into your gas through the pump, if you so selected. Give me a f'n break...

Nowhere but Texas!

How's that ethanol thing work anyway? They leave the corn silk in and grind it up to softly clean the injectors as it passes thru?

[dedwards0323]

Originally Posted by MyOtherRidesAVette

but, I was out in Cedar Park (west Austin) the other day, out by Lakeline Mall, and got gas at an H.E.B. Never saw it before, but they had a "pay to add" (big $$$$), injector cleaner additive, that would be added into your gas through the pump, if you so selected. Give me a f'n break...

Nowhere but Texas!

How's that ethanol thing work anyway? They leave the corn silk in and grind it up to softly clean the injectors as it passes thru?

The Murphy USA stations around here that are located on Walmart properties have the same fuel additives available on their pumps. I think there are 3 levels of additives one can pick from. I've never used the feature, as I tend to use a fuel system cleaner every 4 months in a tankful of gas. And I try to stay away from stations with ethanol blends. Getting harder & harder to find them.

[dedwards0323]

Just filled up the 2006 ragtop & got only 16 MPG! Went back & checked my records and the last 3-4 fillups have dropped from the typical 21-22 around town performance.

Also noted that at about this timeframe, Berta had an incident with the ragtop on her way home one day. She swerved to the side of the curb after making a LH turn at a light in Simpsonville. She was sitting in the intersection when the light turned yellow & completed her turn rather quickly. She swerved to the curb because an ambulance was fast approaching and had already begun to sound the siren and emergency horn. But in going to the curb quickly, she hit the curb & flattened both tires on the RH side of the car. Had to get a tow truck to get the car home so I could get new tires installed. Strange thing is, she didn't scrape either of the wheels against the curb. No signs of "curb rash". Still not sure how she did it.

Anyway, the MPG started dropping off right after that. I'm thinking that a fuel line connection is either loose or damaged causing us to lose gas and get poor mileage.

I also saw the post about the 2.5 VW recall regarding fuel line leaks that could occur due to some rubbing & chafing with components of the PS unit. This could also be my issue.

If the weather continues this warming trend for the next couple of days, I'll get the ragtop up where I can crawl around some.

Anyone got a "heads-up" for me on where to look?

[miffmole]

Originally Posted by MyOtherRidesAVette

How's that ethanol thing work anyway? They leave the corn silk in and grind it up to softly clean the injectors as it passes thru?

The whole ethanol scam makes no sense at all...unless you're a corn farmer and then it's great.

You put 10% ethanol in the gasoline, and presto, your MPG goes down roughly 10%. Where's the gain? Where's any less dependence on foreign oil?

Plus, you're lessening the food supply and causing price increases there.

[MyOtherRidesAVette]

Originally Posted by miffmole

The whole ethanol scam makes no sense at all...unless you're a corn farmer and then it's great.

You put 10% ethanol in the gasoline, and presto, your MPG goes down roughly 10%. Where's the gain? Where's any less dependence on foreign oil?

Plus, you're lessening the food supply and causing price increases there.

Where is this 10% reduction in mpg coming from? Between all my vehicles my annual mileage on them probably averages 150,000 miles. I track every gallon that goes thru every vehicle and see the mpg on every tank used. Three vehicles are in and through gasoline markets all over the country. Really! One that covered 90k miles this last year has been to the four corners, Maine, Washington, SoCal, and Florida, Markets with ethanol, and without, and trust me, the mpg doesn't vary 2%, from tank to tank, and this mostly due to not quite full fill-ups, mountainous locations, etc. I actually see some of my better gas mileage in ethanol heavy states, and Texas is one of them. But I attribute part of this to low elevation, fairly level terrain, more moderate and uniform temperatures, and the legal ability to run at higher more consistent speeds. Most of our primary divided and undived State four laners are 70mph and we have 80mph on hundreds and hundreds of miles of Interstate.

I would be interested in seeing anyone's actual test data, proving what you are saying.

The other advantages to ethanol, an alcohol, are that it reduces the moisture in gasoline, and helps to deminish varnish deposits from carburators and fuel injectors, while at the same time I am aware that it can cause damage to engines that do not support the use of ethanol blends (pre-mid 90's), and can also cause filtration problems due to it's cleansing and break down of corrosion in the fuel tank. (I have done some research)

MORAV

[miffmole]

My overall MPG was reduced immediately from 30 MPG to 27 MPG with the advent of ethanol "enhancement." Thats' a 10% reduction.

I've logged every fill up since 2/27/2008.

[MyOtherRidesAVette]

Originally Posted by miffmole

My overall MPG was reduced immediately from 30 MPG to 27 MPG with the advent of ethanol "enhancement." Thats' a 10% reduction.

I've logged every fill up since 2/27/2008.

Okay, I believe you. And yes, that is 10%, outrageous! Are you running premium?

My experience is with, and I'm sorry, but real engines, in real cars. Don't get me wrong, I've owned 3 NBs and currently still have two of them, a '03 1.8T and an '05 2.0, having just added '05.

Have you talked to anyone about having your engine tuned for the gasoline reformulation? Perhaps a change in spark plugs? I wouldn't hav thought these engines that sensative to the addition of the ethanol. Why not just buy an ethanol free brand. We have both available here, and as a matter of fact, I going to try running about 10 tanks of each, and see what I see.

MORAV

[miffmole]

Originally Posted by MyOtherRidesAVette

Okay, I believe you. And yes, that is 10%, outrageous! Are you running premium?

Yes, I use premium exclusively...The MPG reduction is pretty much universal. Look over some of these articles, etc:

ethanol reduced mpg - Google Search

Have you talked to anyone about having your engine tuned for the gasoline reformulation? Perhaps a change in spark plugs? I wouldn't hav thought these engines that sensative to the addition of the ethanol. Why not just buy an ethanol free brand. We have both available here, and as a matter of fact, I going to try running about 10 tanks of each, and see what I see.

MORAV

It's pretty tough getting 100% gasoline here in S. Carolina. In fact, I know of only one place near me now, and it's 18 miles away. My last fill-up there was $3.23 per gallon for 93 octane premium.

[MyOtherRidesAVette]

Have you talked to anyone about having your engine tuned for the gasoline reformulation? Perhaps a change in spark plugs?

[Smileybug]

Its a pretty well known fact that the ethanol drops your mileage. The energy content in ethanol is less, so adding ethanol to gasoline IS going to drop your mileage (I should say that this is true with the corn ethanol...I think other types are better but they aren't universally used like the corn ethanol [thanks corn lobby!]).

I will say that I don't know if there is ethanol in the gas around here. I've been making it a point to check the pumps everywhere I fill up and no where that I've seen here in NC says one way or the other. I'm assuming that means that there is none, but I find it hard to believe that we don't have much ethanol gas, especially since its dang near everywhere now. I know when I was with my parents last week they filled up in VA and the pump had ethanol.

I know I rarely see 30mpg on the highway anymore and it used to be no problem to get that when I first got the car almost 6 years ago, which was before ethanol was really prevalent in gas.

[MyOtherRidesAVette]

Originally Posted by Smileybug

Its a pretty well known fact that the ethanol drops your mileage. The energy content in ethanol is less, so adding ethanol to gasoline IS going to drop your mileage (I should say that this is true with the corn ethanol...I think other types are better but they aren't universally used like the corn ethanol [thanks corn lobby!]).

I will say that I don't know if there is ethanol in the gas around here. I've been making it a point to check the pumps everywhere I fill up and no where that I've seen here in NC says one way or the other. I'm assuming that means that there is none, but I find it hard to believe that we don't have much ethanol gas, especially since its dang near everywhere now. I know when I was with my parents last week they filled up in VA and the pump had ethanol.

I know I rarely see 30mpg on the highway anymore and it used to be no problem to get that when I first got the car almost 6 years ago, which was before ethanol was really prevalent in gas.

I think you are probably not getting ethanol, as I believe it is Federally mandated that it clearly be indcated at the pump. If you mpg has dropped significantly I would be looking for the culprit. Might be time for a major tune-up, could be a fouled plug issue, timing issue, bad spark plug wires, etc.

MORAV