how much whte smoke is normal

1998 lesabre 134000 miles. runs good, gas mileage dropped a lot year or two ago otherwise no problems, still plenty of power.

I do not normaly drive this one. It seems to blow white at start up maybe sometimes on exceleration when i am folowing. Not sure if I remember that right. but how thick and for how long is it ok for the exhaust to be white?

concerned about the stupid plastic melting on me. Had buick repair that but cant feel trust that they did it so it wont happen again.

First are you loosing coolant? Some vapor is normal depending on temp and humidity.

At start-up, especially on cool days, the usual white "smoke" is water vapor (steam) and should go away once the engine and exhaust system are fully warm. Burning oil typically gives more of a blue tinted smoke.

Runs well and plenty of power. yet fuel economy has dropped. That can be the result of any of a number of items such as:
lazy O2 sensors (running rich)
stuck open thermostat (engine running colder than design and runnign rich)
worn spark plugs

It is not loseing coolant. Plugs are fine put them in one or two years ago and look good when i pulled them recently. Dont know how to check the sensor, I used to know a buick mechanic and seems like he told me they rarely go bad.
The thermostat is something I never considered. Can that account for 5 or more mpg drop and not notice any running issues?

with the white smoke it is wispy, not heavy and I first didmissed it, thinking like yall.
seems like car should have been warm enough. I have noticed some other cars too, and it made me wonder.

Can that account for 5 or more mpg drop and not notice any running issues?

What does the temp gauge show? If the t-stat is stuck open, the engine will tend to run cold and take a long time to reach normal operating temperature. The engine will tend to running rich in warm-up mode. If the temp gauge tends to sit around 1/4 scale or lower, you may have a stuck-open t-stat.

A lazy, but not so bad as to set a code, O2 sensor can similarly cause the engine to run rich.

Not that changes in driving conditions, driving style, seasonal conditions, and gasoline blends can also contribute to significant changes in MPG.

Whether or not they can cause a 5 mpg drop in fuel economy is hard to say not knowing other circumstances.

FWIW: on my '04 the difference between suburban driving and open road with occasional stops about 20 mile apart is about 7 MPG. On my '95 Saturn SL2 the difference between January/July and October/April for my 10 mile northern VA commute is about 5 MPG.

dpalomaki
thanks for the reply. My car does not have a temp gauge. I do have a infrared unit can that tell me what I need. I never thought of it before. I thought that if it is running cold there would be signs on the plugs. It does take a little while to heat up the heater in cold weather. My wife normaly drives this car and does not complain enough to make me get around to changing the stat. her drives are either short and would get little improve in the heater or we fairly quickly get on the freeway and it heats up quick. i think i will change the stat anyway and see.

Am I wrong thinking if the o2 was off the plugs would show some sign?

before the drop or even after we get little difference in mpg driving freeway or town unless it is serious big city lots of lights etc. still , I think never 5 mpg. I get better mileage than my wife for certain but even her driving got close to mine mpg. One of the things I like about this car is the great mileage on the freeway and still get great in town and we have the size too. Farely flat open road we got 34 sometimes 33 nearly all other times town would be (dont remember for sure) 32 ish? generaly

In cold weather, the heater should be giving some output within a couple miles, and a good amount of heat within say, 4 or 5 miles. If the t-stat is stuck open, the heal will take more like 6-7 miles and will never be very good in real winter weather. With a properly working t-stat the heater can roast you out in just about all but -20 F weather.

Not sure if you car has a pressurized coolant recovery tank, or a conventional radiator with a fill cap on it, but in any case, on a cold engine there should be minimal flow through the radiator until the engine is near operating temperature. Sometimes you can see the flow through the fill cap, and sometimes you can check it by the feel of the radiator inlet hose at the radiator. If the t-stat is stuck open, there is substantial radiator flow immediately and the hose will warm up gradually as the engine warms up. If the t-stat is working properly the radiator inlet will not heat up much until the t-stat opens and then it will heat up quickly.

If you have an OBDII scanner it will read the engine temperature. (It is a handy tool for work on '96 an newer cars.)

Running consistently rich, over time, will probably show on the plugs, but it may not for many miles.

34 in urban/city driving, is that KM/GAL ? We get about 27 MPG on the open road using A/C, around 20-21 in urban driving.

Thanks again. I dont know why I have not given much thought the stat. I dont expect recovery of all my gas miles but should be improvements. Our heater experience before and now somewhere in between your description.

This car and I understand I am not alone, gets very good gas mileage. That is MPG. 34 would be on trips all freeway but with a/c maybe a pass or two and a rest stop or two. That was ideal. We did not get that for instance when we take a route to the coast and go over the pass. That trip would be 31-33 mpg.

I have not gotten around to investing in a meter. I wish someone would give me one.