legacycentral bbs

Hey


It seems my car is eating gas a little fast I only get about 250-300km a tank

I know there are dozens of possible causes just hoping you guys could list a few.

I dont drive it hard enough to get such low milege and I rarely get the rpm's over 4500 .

Another Q?? I had is how much gas does this car eat when at idle ? cause I do let it warm up for about 20 minutes every morning


Thanks

o2 sensor?

20 minutes? Every morning? That's a big part of it, I noticed this with my wagon. I drove highway all day and got great mileage for the first half tank or so then got only half that for the rest, that was from warming it up every morning for work and driving 7 miles, let it sit, warm it up, repeat.

Faulty injector?

Low tire pressure?

Extra weight in the car?

Failing Spark Plugs, Wires, or Coilpack?

Excessive back pressure (ex: cat)?

I say it's this 20 minute start-up business. I used to let my car warm up for about 10 minutes, scared coz the engine is Al, but I soon learned that you're not doing the car any good, you're only wasting gas.

The best thing to do is start the car, maybe a 30 sec warmup, and start driving it slowly. Do NOT get on it when it's cold, aluminum engines don't like it. Driving around slowly will warm it up faster, and you will actually be making progress toward your destination while you do it.

Remember, your car gets its worst mileage sitting still. You're using gas but not moving the car.

is that really true? I would think it would get worse mileage going slow, 10-20 mph, than idle.

Just drive the car....don't bother warming it up......I don't think I've ever "warmed" the car up......it warms up as I drive....

THAWA wrote:is that really true? I would think it would get worse mileage going slow, 10-20 mph, than idle.

Are you joking?

Mileage is measured in miles per gallon. If the engine's idling with the car stationary, mileage is zero by definition. The only other way for it to approach zero is for gallons to approach infinity.

I'll second (or third or fourth or whatever) the suggestion to just drive it. Just go easy on it -- stay off boost, stay at low engine speeds, etc. A bonus is that it'll also warm up your transmission fluid (which happens very slowly when stationary) and differential fluids (which doesn't happen when stationary).

I remember one time I locked my keys in my old Sport Sedan while it was running . It burned through like half a tank of gas in the few hours it took me to get my brother to come to my rescue.

im sorry i wasnt thinking in miles per gallon.

Ive used mine for years in the winter. Have it set on a timer for couple hours before going to work. Works good. Dave in Tahoe

THAWA wrote:im sorry i wasnt thinking in miles per gallon.

Oh... gotcha. Yeah, I'm sure at idle the engine is using the least fuel per unit time (except when coasting, maybe).

You guys are letting your car run for 20 minutes or more in the morning? I have to say that you are honestly pretty dumb.

Carbon build up is a problem to begin with in subaru's. There is no reason to have the car warm up for more than 3-4 minutes at most. Id love to see the caked pistons and valves you have created.

I just warm mine up for about a minute to whenever the idle drops when it's excessively cold and then just shift easy and keep the revs low until she warms up.

You shouldn't have to warm it up so long - it's not an old steam carriage.

Steve

I let my turbo warmup for a few minutes then then shift easy, keeping it under 80k/hour and out of 5th untill coolant temp has stabilized. I love this motor far too much to abuse it

Mark

ciper wrote:You guys are letting your car run for 20 minutes or more in the morning? I have to say that you are honestly pretty dumb.

Dude, there's no need to say such personal things. If you really feel like you have to use the word "dumb" at least use it to describe peoples' actions instead of the people themselves.

But, yeah, I agree that it doesn't make much sense to let your car sit for 20 minutes idling. Unless you're spending those 20 minutes cleaning off all the snow.

I'm a big proponent of driving cars as they were built to go not sit - they are dynamic entities - joggers, not couch potatoes. Warming up too long is up there with constant traffic or never hitting redline. I hit redline in three gears several times a day, downshift for turns, and corner at over 5k constantly. Keeps the engine clean of deposits and everything. Ever drive an old hearse? (I have. Always wanted one) Anyway, the biggest problem is finding one that runs well. They're always driven so slow that they never want to move. They get lazy like people (that's the reason I'm going with - you scientific unbelievers can keep quiet). An object at rest tends to stay at rest. Make your car exercise and she'll want it and run better for it. But don't take my word - the odometer's got 234k and has only recently given me any kind of driveability issue (a very minor one) with the exception of old fuel filter caused hesitation. Just replace all fluids and consumables on schedule and you shouldn't have to baby it. It's not an Alfa Romeo Montreal.

Steve

vrg3: okay,

It would be a dumb choice for someone to let the car idle for more than 4 minutes in the morning.

I was told to never let my other car warm up, eating alot of gas being one of the reasons.


But when it is -20C 20 minutes is not long enough. + my car doesn't agree with low engine temp.

What I do with my other car when its cold is jam a stick between the seat and the gas pedal to keep the rpm's at 3000.

This would stop carbon build up right??

ciper - Okay, I agree with that, unless there are some weird circumstances that require it.

turbonator - I was under the impression that it was wide-open-throttle that helped prevent carbon buildup. Idling at 3000 rpm is still very low engine load (very high vacuum).

You say 20 minutes is not long enough -- not long enough for what?

I hear what you're saying about the cold - mine takes a while to warm up in extreme cold, too (EPA would love it), but I find driving it gently warms it much quicker than sitting at a constant speed. However, if you have driveability problems or something that make it highly unpleasant, do whatever works for you. As long as you hit redline every so often, it should keep it clean.

Slightly off topic: do you think Subaru has carbon build up issues due to rich-leaning fuel maps designed for better response? I had a boss who also loved Subarus (these were EA82's, though) and he said that he always had trouble passing emissions (and this was before they introduced dyno testing). I wonder if maybe it was a hydrocarbon issue. I have seen lots of Subarus burning black. Not that I have any problem passing with mine...

Steve

If your car is taking an extremely long time to warm up, have you checked your thermostat or even replaced it recently.....more then likely it needs to be replaced.

That's a good point, Josh. Thermostats (if they're well-made) tend to stick open when they get old.

Would that explain why my car takes so long to blow heat in the mornings?

Albeit I do live in eastern canada where -20 mornings mid winter are normal, should it be taking 10 + minutes to warm up the car? (temp guage moves off cold to middle)

yup.....I'd start with a new t-stat and see how things are.

I'm also going to say, make sure you buy one from the dealer, because the non-subaru ones are different and don't work the same. I speak from first hand knowledge.

I don't think that's too far off the mark, but you might want to check it anyway. It does come fully up to temperature and stabilize eventually, right? I know mine can take about 10 mins in extreme cold in I just idle it. Driving takes about 5 (or 2-3 town miles).

Steve

Yeah, it warms up quite nice eventually, colder days it takes 10 minutes or so.

Here's another question, engine and cold weather related...

When I leave my car sit for long periods of time, ei over night or the weekend, when I start it cold, before it warms up there is a ticking sound or knocking from the valves or lifters or something.

Should I be worried about this? It goes away once it's warmed up and runs fine no either way...

Just curious, I'm still a subaru newb.