There's also a good probablility the computer cuts the compressor off when you downshift automagically, too...
Re: your "test"--I wouldn't put too much faith in the absolute values of those onboard systems for small differences and short distances particularly. Your data doesn't negate physical reality other than the zero difference at the lower speed differential which is quite likely owing to the imprecision of the display as much as anything (as you note)....
In a recent thread we had comments about fuel mileage, SUV's etc. I did some research using my full sized car and the instant read mpg on the computer that it has. I took readings on the same places, seemingly very level. Keep in mind the gauge read whole numbers so decimals are not show but may be rounded.
Using cruise control to keep the human element out, I drove at 70 mph, 65 mph, 60 mph. There was no shown difference between 65 and 70. When I made the run again at 60, is showed a 3 mpg increase.
I drive about 12,000 mile a year on highway (total is about twice that). Saving the 3 mpg saves a total of 52 gallons of gas. At today's price of $3, my savings per year is $156.
Now, driving at 70 mph, I will spend 171 hours at the wheel. Driving that same distance at 60 mph, I'll be spending 200 hours for the same trips. So, to save $156 I have to give up 29 hours of my free time. The actual mpg will vary on different cars, but that is what I was able to do with a Buick LeSabre. I also don't notice any difference with the AC on or off so I go for comfort. YM WILL V Ed
Or you can say you are paying about $5.50 an hour to drive 70 instead of 60 ( or earning $5.50, tax free, driving at 60).
The "Myth Busters" did a segment on driving with AC or windows open. It was not very conclusive I thought. I think the windows open won but the guy with the AC on was freezing. They were not diving at 70 mph either.
That is for the saved 29 hours. For the full time it is more like 91¢ per hour.
I think speed and car design would make a difference. On a smaller engine, the AC would take more power as a percentage than a larger engine. Years ago, I'd shut the AC off to pass another car or to struggle up a hill. On my car, I cannot feel any difference. Compressors have improved.
I look at is as your driving 70 instead of 60 you saves about 10 minutes. The 91 cents is the savings for the 10 minutes, not the whole hour. Therefore the $5.40 an hour for the saved time.
I wish I had as much time on my hands as you do.
I have a 35 minute commute to work each morning. Aside from listening to the radio or playing a CD, what else is there to do? Perhaps you need a longer commute
Dripping 5mph to 55 mph would likely save more than the 5 mph between 60 & 65.
You may be right, but I've not been able to try that. If I slowed to 55, I'd be run over. I'll have to do out late at night, not morning traffic.
Wow, you are brilliant. Thanks for joining in.
If some of these whiney ass indigent bus riders around here had their way, you'd have your legs amputated to the knees so you could drive a Miata.
YM Will V - Correct - A lesabre will show little difference, as you noted, between 65 and 70. A 4 cyl car will show more difference at those speeds. The smaller engines will need to work harder to maintain, hence use more gas. Unfortunately its all relative. The lesabre mpg may be, lets say, a difference of 20mpg to 23 mpg at 65mph and 60mph respectively. the little 4cyl car may show a larger difference but may be more like 22mpg to 28mpg at 65 and 60 respectively.
Not to knock you for having a large car though. You have every right to drive what you want and spend your money how you want without criticism. (I drive a Chevy Suburban and a Chevy Silverado!)
I've not taken any readings over a period of time. However, I do remember one time I was hauling through Ohio, on the way home from Indiana. It was a warm summer day, and I was running the AC here and there to take the edge off the heat. The MPG went from about 20 usual to about 17.
I didn't run the stats, how much more it cost, or how shorter was my range on the tank of gas. However, I do believe that if I was trying to escape Hurricane Katrena, I'd have been wise to leave the AC off. Too many people running out of gas. Don't want to be one of them.
id like to get a toyota corrolla ,,,for the mileage , but im 6"5" and none of the small cars have enough head room. my grande marquis gets 18 on the highway 13 city.
mathematicians, not "mathemeticians" there, not "their"
Plonk!
Hey nick: PLONK!
: >> Using cruise control to keep the human element out, I drove at 70 mph, 65 : >> mph, 60 mph. There was no shown difference between 65 and
: >> I drive about 12,000 mile a year on highway (total is about twice that). : >> Saving the 3 mpg saves a total of 52 gallons of gas. At today's price of : >> $3, my savings per year is $156. : >>
: >> Now, driving at 70 mph, I will spend 171 hours at the wheel. Driving that : >> same distance at 60 mph, I'll be spending 200 hours for the same trips. : >So, : >> to save $156 I have to give up 29 hours of my free time. The actual mpg : >> will vary on different cars, but that is what I was able to do with a : >Buick : >> LeSabre. I also don't notice any difference with the AC on or off so I go : >> for comfort. YM WILL V : >> Ed : : : mathematicians, not "mathemeticians" : there, not "their" : : Plonk! :
we should all push to have the traffic signals synchronized so we could get better milage in the city.
save time save brakes save gas reduce accidents...
It should be a law that lights within 2000 feet of each other MUST be synchronized.
Mark
I have a smaller car too. I get the same mileage and better acceleration as the larger newer car. Same engine, better technology. If I drove around the city all the time, I'd go for small. I do to much highway not to have some comfort. I do too much driving period, not to have some comfort.
I also saw the MythBusters show about the a/c vs. gas mileage. What stuck in my mind about the "test" was that the people standing around outside were wearing jackets! The results would have been a lot more accurate if it had actually been in hot weather. The compressors on the vehicles probably didn't even run 50% of the test. I do agree that the a/c affects small engines a lot more than larger. I have a 94 Ford Aspire that got about 40+ mpg on two 500 mile trips I took in it last winter. I have not actually checked the mileage with the a/c, but it seems to knock off about 5 mpg, both in town and on the highway. Larry
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