Fuel mileage

I didnt go into great detail to begin with so now I will I bought car new 2003 and regularly check tire pressure also use sinthetic oil clean filters on regular basis took car in for tuneup told it was waste of time have 65’000 miles app. Been back and forth to Florida three times and each time fuel mileage gets bad further south I go. I might add I use premium fuel only. Thinking it may have something to do with elevation only thing I can think of. Dan clegg

It’s possible that the mileage is dropping because the area you’re going to in Florida is much more congested.

Exactly where are you going from and where are you going to?
What mileage do you get at home and what mileage do you get in Fla.?
How are you measuring the mileage exactly?

The vehicle you drive doesn’t require premium or a high octane fuel. And there’s no benefit in using this fuel. Did you know that using a high octane fuel in an engine that doesn’t require it can result in combustion chamber carbon deposits? And if done long enough the carbon deposits build to a point where a high octane fuel MUST be used in order to eliminate the pinging as a result of higher compression from the carbon deposits.

Tester

Tester,since so many people read these mileage and octane posts can you provide a link to the information you have presented?

On the IT Forums I frequent readers would just post one word, Proof.

Tester

Broken link for me.OK link works, but I need more (like a TSB or a textbook, or several textbooks to buy into this,the author citation is not so impressive)

Youre right Im sure Fl is more congested in Idaho I would get 33 to 35 mpg highway and 29 in town and some highway mostly farming area mileage is measured by the computer in car in fla 23 24 highway best I can do city maybe 17 mpg

I didnt know that when I switched to higher octane mileage went up but in Fla it doesnt seem to matter so by all means I’ll go back to lower octane fuel thanks

Why would premium fuel leave carbon deposits?? The oil companies would have us believe premium fuel will keep your engine sparkling clean and free of deposits of any kind…They even infer that if you have been using that cheap unbranded gas (that they also sell) you can clean out the deposits by simply using their premium fuel…I doubt the Buick the OP is driving cares what kind of fuel is pumped in its tank…

Three things that reduce mileage. Traffic, headwinds and rain…

and theres a lot more traffic in fla than Id Im begining to think maybe that has alot to do with but you wouldnt think Id lose 10 miles per gal

I have found those gas mileage calculations to be off by quite a bit. I’d recommend that you actually measure you mileage the old fashioned way. Fill up, record the mileage on the odometer. After each fill up, record the mileage and after three fill ups, then do the math. Do it at home and in FL, I think they will be closer than you think.

It may have more to do with high altitude verses sea level than north verses south. Thinner air has less air resistance and also effectivly reduces your engine’s displacement.
Our Honda Element ususally gets 22-24 mpg in central TX, effectively sea level, but when we go to Taos, NM with it, we often get 30 mpg with it.

Hilly terrain, if it’s not so severe that you have to ride the brakes on the downhills, also makes you do the old hypermiler trick of pulse-and-glide, that is using the engine intermittantly at a high power level and then gliding with the engine idling. Florida, being flat as a billiard table, has you driving at a steady very low power.

And, you don’t use the A/C more , or roll the windows down, the farther south you go?

Unburned fuel+hot combustion chamber=carbon deposits.

Tester

It may have more to do with high altitude verses sea level than north verses south. Thinner air has less air resistance and also effectivly reduces your engine’s displacement.

I believe you will find that the effect is far too small to measure. Anyone have the actual data (like the average air pressure at sea level and at say 1,000 ft?)

Good point. Last time I checked I think Florida was hotter than Idaho.

I believe you will find that the effect is far too small to measure. Anyone have the actual data (like the average air pressure at sea level and at say 1,000 ft?)

The effect of altitude is not “too small to measure”

At 6000 ft, air density is about 80% that of sea level air.
At 8000 ft, air density is about 74% that of sea level air.

This empty water bottle was completely full of air when the cap was sealed in Taos, NM, 6950 ft above sea level. This is what it looked like upon arrival in Austin TX, 600 ft above sea level.

Thanks B. L. E.

Your car is rated for 17 MPG city and 27 on the highway. I have a hard time believing you were getting 29 MPG in the city and 35 on the highway. But your current mileage is very close to what the car should be getting. I doubt there’s anything wrong with it.