Anyone else noticing a significant drop in their gas mileage?

[Carni]

OK I know gas prices are up and I know that people are suffering sticker shock

BUT with that said I know about 5 people right now who insist that they are not getting the same gas mileage that they were getting previously.

One has gone from about 24 miles per gallon to about 17--They have been to a mechanic/they can't find anything wrong etc etc. They even bought a locking gas cap thinking it was being stolen.

To get to the point they started checking around and found several people that they know complaining about the same thing.

I am wondering if in addition to hiking up prices if the gas is being cut with something?

Just wondering if this is a wide spread thing or if I just know a bunch of people with hidden car problems?

[xray s]

1. Do you live in an area that switched to ethanol from gasoline?

Some parts of the country use straight gasoline without ethanol. Straight gas gets much better mileage than ethanol. If the area you live in has switched to ethanol lately, that would explain it. (The reason for the drop is alcohol has less energy producing capacity then gasoline)

[Carni]

4. The people I know who are complaining are in virginia

I don't live there but I wonder if that is what the deal is there?

[punpirate]

10. I doubt that would account...

... for the loss of mileage described, and here's why--there's a limit to how much alcohol that can be added to gasoline without the addition of some comparatively expensive emulsifiers. That upper limit is about 11-12% by weight (about 10% by volume). Much beyond that, the alcohol causes stratification in the tank, separating out into layers of gasoline, alcohol and water.

You're right that ethanol has less fuel energy. That difference is roughly 11,500 BTU/lb for ethanol and depending upon grade, 16,600-17,200 BTU/lb for gasoline. Therefore, ethanol has just a squeak over two-thirds the fuel value of gasoline. For a full tank of fuel in the typical tank today (say 15 gallons), the substitution of gasohol (10% ethanol) for straight unleaded gasoline would be an effective change in total fuel value of roughly 3.5%. This would be reduced slightly because of the oxygenation of the fuel, providing more efficient combustion at slightly lower combustion temperatures. Let's say the difference is 3%. For a car normally getting 25 mpg, this change in fuel value would result in a directly proportional change of - 0.75 mpg.

No, something else is at work, I think, and there are a number of possibilities. The weather in many parts of the country has been colder and wetter than normal. This would increase the chance of water seeping into underground tanks, and would also require more warm-up time or more time running under enriched mixture. Mileage in cold weather can go down as low as a mile or two a gallon for the first mile.

Additionally, refineries change the blend of the gasoline according to season. More light volatiles in winter to encourage faster starting and less in summer to prevent vapor locking. Getting the wrong blend for conditions at the tail end of one season, or the beginning of another could cause some mileage problems, if the ambient temperatures weren't cooperating.

Note that no one mentions where they are, if the weather was noticeably different for the time of the prior fill-up, driving conditions (particularly time spent idling in traffic) or what fuels they normally buy.

There are so many variables in this that I wouldn't jump to conclusions. As for gasohol, the math just doesn't add up to several mpg difference.

Cheers.

[tridim]

2. I got 5 mpg less on my last tank

I assumed it was just a fluke. You might be on to something.

[Carni]

5. I think my mileage is down too

But I haven't had my current car for very long and I am one of those people that has never really paid attention to their gas mileage.

[Ironpost]

3. Interesting, keep us posted, I think mine is less also.

[Coastie for Truth]

6. I have a 5-7 mpg difference in the Corolla

when the air conditioner is on.

[xmas74]

7. I have an appointment w/ my mechanic tomorrow.

I have been getting less gas mileage and my engine is making a knocking noise-like the last time I got water in my gas line. It had a tune-up 3 weeks ago and then it was perfect. This just started in the past week. Strange, isn't it.

[GoddessOfGuinness]

8. I heard a radio news report last week that mentioned faulty pumps...

There were a particularly high number of them in VA.

Also, they mentioned that we may not all be receiving the octane grade that's posted on the pump; but at present, those responsible for checking to make sure pumps are working have no way to test the octane.

I'm in MD, just outside DC. I noticed lower mileage last week. Haven't driven much this week, but it was definitely off then.

[sendero]

9. I check my mileage....

... on every tank. I have found over the years that some gas (Chevron, Texaco, Citgo) is better than other gas (everybody else), to the tune of 2 mpg or so.

However, my current tank is on target to get the 30 mpg or so I would expect.