I was noticing the same thing the other day. I was driving around and i was like my gas mileage is horrible. Then i thought like one of those gothic kids that think the government is trying to enslave us...and i was like maybe they are putting something in the fuel to make it less efficient lol.

Now with your "evidence" i think my case is true!

-Sean

 

My experience is it's not BAD to warm it up. It just wastes gas since there is no danger to driving after 30 seconds of warming. Bonus is that the car also warms up faster when under light load rather than just idling. Remember, light on the gas until it's fully warmed up.

 

It may not be bad for the mechanicals of the car, but in relation to this thread it's horrible. Why? Because at idle you are getting 0 miles per gallon. Thereby decreasing your gas mileage.

 

you guys are lucky, i only get 350 km a full tank while you guys are getting 300+ miles

 

I'm not making this up The best way to warm up a stone-cold engine is to let it idle for around 30 seconds and then start driving at a moderate pace (sub 2500rpms). Advantages to doing this:

1) When the engine is cold, it's running extremely rich and inefficiently. Letting it idle for a prolonged period of time uses excessive amounts of fuel. The quickest way to warm up the motor is to start driving and you'll use less fuel doing it.

2) Excessive rich conditions can lead to fouled cats because the cats get drenched in fuel and since you're not driving yet, they take much longer to light off.

3) Letting the motor warm up at an extended idle doesn't warm up other important components like tranny and diff fluid. Many people think since the motor is warm, they can drive like normal without considering the tranny/diff. This could be a costly mistake in the long term.

4) Letting the motor warm up by idle can lead to hot and cold spots on the motor. Oil doesn't get distributed as effectively, especially on the upper portion of the motor like the VTCs and rockers.

 

Problem is, it takes a lot of self control to keep it under 2500 RPM

 

Once I get a good mpg baseline (recording fillups and calculating mileage now), I'm going to try this stuff:



http://www.amsoil.com/storefront/api.aspx

"Improves fuel mileage an average of 2.3% and up to 5.7%. Reduces emissions such as hydrocarbons (HC) up to 15%, carbon monoxide (CO) up to 26% and nitrous oxides (NOx) up to 17%. Restores power and performance. Reduces the need for costly higher octane fuel. Reduces noise from carbon rap and pre-ignition. Offers better vehicle drivability and smoother operation."

Moneyback guarantee, so why not?

+1 on the long idling, not necessary and a waste of gas.

 

your oil pressure is also lower when you are idling so if you idle for a long time the top parts of the engine that need oil are not getting as much (this is what I have been told)

 

I noticed that too, I'm down to 17 mpg from my usual 19-20.

Best I've ever gotten was 25, worst was like 12 but I was 100+ for an hour or so.

 

So glad I read this thread. I was beginning to freak out. Thought something was seriously wrong. Definitely going to check the air filter. I know gas mileage varies but this last time around there has been a significant change. I fueled up today and I noticed "10% eythanol" on the gas pump. Typically I get over 300+ miles out of a tank and recent filled up at 250-260.

 

Hah. I'm lucky if I get 250 to a tank in the summer. I should pay attention to what I get next time I fill up. My work is 15 minutes from my apartment, and probably only 5-7 miles. I do all city driving.

 

Keep in mind... when your gas light comes on you generally have 5 gallons left.

The gas tank is 20 Gal. I've gone close to 500 miles in my car. 5AT. I got 28 mpg one trip.

I agree totally with not spending too much time warming up your engine in the driveway on idle. If you do that you should notice that your tranny shifts much harder because it is not warmed up yet.

 

thats about the same as i get . ive seen lows of high 17's per gallon and my best is under 20mpg . i drive pretty fast though .

 

I changed my plugs and my milage jump alot. Maybe its time for a tune up for your ride?

 

10% ethanol is the standard year round; its nothing new.

I agree, it's not great to warm a car up by idling due to low oil pressure combined with thick oil. It's probably not detrimental but I'd avoid it if you can.

Fluctuation in gas mileage is pretty normal, especially in winter. The cooler air and higher atmospheric pressure do cause an increase in consumption. However this does equate into a slight increase in power. The stat I've heard is about 2% HP increase for ever 10 degrees C.