posted
In the last month and a half, I've seen my gas mileage dip slightly on my new Saturn beater car. It hadn't really concerned me, though I thought that with the coming of the cold weather, it would improve. However, I had started noticing that my tires seemed a little low and, having finally found my tire gauge this morning, went and checked my tires. Sure thing, one was at 32, the other three were around 22-23. So I put them all up to 32. My question is: Will low tire pressure cause gas mileage to fall?
------------------ Jim Mac '98 Silver SS #108
Posts: 1907 | From: I hope I'm not repeating myself. Again. And Again. Stop picking on me! Waaahhh!! | Registered: Feb 2000
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posted
Yes. But cold temperatures and short trips are gas mileage killers too. e.g. I'm getting 10 mpg with our Jimmy through the current really cold snap.
Posts: 4222 | From: Winnipeg MB CA | Registered: Feb 2000
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posted
Jim's comment about the pressure differences brings up a question - what in the heck causes those pressure differentials? For example, I checked the tire pressures in both my vehicles, and both had at least one tire that deviated from the others by >5 lbs. Yet they don't have slow leaks, were checked cold in a garage (no sources of heat to warm one tire more than another). If I randomly check pressures at any given time, this seems to happen (not always by a >5 margin), and usually with different tires each time. What gives?
Posts: 126 | From: DSM | Registered: Oct 2000
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quote:Originally posted by Jim Mac: In the last month and a half, I've seen my gas mileage dip slightly on my new Saturn beater car. It hadn't really concerned me, though I thought that with the coming of the cold weather, it would improve. However, I had started noticing that my tires seemed a little low and, having finally found my tire gauge this morning, went and checked my tires. Sure thing, one was at 32, the other three were around 22-23. So I put them all up to 32. My question is: [b]Will low tire pressure cause gas mileage to fall? [/B]
Underinflated tires cause additional rolling resistance = lousey gas mileage.
Underinflated tires have a smaller rolling circumference (yeah its pickin') therefore less circumference inches per revolution = lousey gas mileage.
Ambient air temperature affects tire pressure. Cold = lower pressure than what it was hot.
posted
I do not think it's your under inflated tires at all... It's probably that you have finally mastered the fearful power on that Saturn and now you're starting to drive more aggressively, sacrificing your gas milage.
OG
Posts: 621 | From: Houston Texas USA | Registered: Feb 2000
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quote:Originally posted by OLD GUY: I do not think it's your under inflated tires at all... It's probably that you have finally mastered the fearful power on that Saturn and now you're starting to drive more aggressively, sacrificing your gas milage.
OG
...yeah...either the fearful power of the Saturn, the wind drag applied by Pluto, or the gravitational effect of Uranus...
quote:Originally posted by OLD GUY: I do not think it's your under inflated tires at all... It's probably that you have finally mastered the fearful power on that Saturn and now you're starting to drive more aggressively, sacrificing your gas mileage.
Yeah, it took me all of 10 miles to do that!
Actually, it's been driven pretty aggressively commuting since Day 1: I do 17.6 miles into work and, when I leave around 9:00AM, I can make it in 16 minutes.
For all those who failed physics and chemistry, let me enlighten you with the little I remember from my Chemical Engineering degree:
quote:PV=nRT
where:
P = Pressure V = Volume n is a constant R can be considered constant (Especially since I've completely forgotten what it stands for!) T = Temperature
If we assume that V, n and R are constant, than we have a direct relationship between P and T. (Although there will be some slight variance in V as P changes, but for the moment we'll consider it to be negligible.) That means that as T decreases, P will also decrease. Again, I don't remember, but depending on what units are used for all the variables and constants, for a specific temperature range, say 0 - 100 Fahrenheit, you can calculate an estimation of the pressure variance per degree. But, since I have absolutely no motivation to try to dredge up that information I tried so hard to drown with alcohol, you'll just have to take my word for it!
------------------ Jim Mac '98 Silver SS #108
Posts: 1907 | From: I hope I'm not repeating myself. Again. And Again. Stop picking on me! Waaahhh!! | Registered: Feb 2000
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For all those who failed physics and chemistry, let me enlighten you with the little I remember from my Chemical Engineering degree: [QUOTE][b]PV=nRT
where:
P = Pressure V = Volume n is a constant R can be considered constant (Especially since I've completely forgotten what it stands for!) T = Temperature
If we assume that V, n and R are constant, than we have a direct relationship between P and T. (Although there will be some slight variance in V as P changes, but for the moment we'll consider it to be negligible.) That means that as T decreases, P will also decrease. [/B][/QUOTE]
...well LA TEE DA...
...I'm sure you figured you'd go far with your PHD until someone informed you that it stood for Post Hole Digger...
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