Poor gas mileage and shifting - Page 5 - Saturn Outlook Online Community
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post #41 of 46 (permalink) Old 08-29-2008, 01:22 AM
 
Join Date: Aug 2008
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Re: Poor gas mileage and shifting

Quote:
Originally Posted by doropallo
I just drove across PA, from Philly past Pittsburgh, and averaged 19.47 miles per gallon. Never went over 70MPH. Still couldn't break the 20 MPG barrier.
doropallo, please check our tire pressure.

Here at this government site, it says:"......Just one psi under-inflated can reduce fuel economy by 3%.". It sounds pretty dramatic, but I wouldn't be surprised if it is true. I ride bicycle a lot and I always inflate the tires to the maximum 70 psi. The bike feels a lot lighter with fully inflated tires. The difference becomes very obvious when the pressure drops to 55 psi.

http://www.fueleconomy.gov/feg/motor...anscript.shtml

Outlook has the high pressure tires. Maximum pressure is 44 psi, not the old 35 psi. So if you are inflating it to 30 psi, you are under inflating it. I think most of the new tires are 44 (my Accord's tires too). I have always inflate them to little over 40 psi, never blew a tire because of over inflation.
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post #42 of 46 (permalink) Old 08-29-2008, 01:58 PM
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Re: Poor gas mileage and shifting

Quote:
Originally Posted by tradewind
doropallo, please check our tire pressure.

Here at this government site, it says:"......Just one psi under-inflated can reduce fuel economy by 3%.". It sounds pretty dramatic, but I wouldn't be surprised if it is true. I ride bicycle a lot and I always inflate the tires to the maximum 70 psi. The bike feels a lot lighter with fully inflated tires. The difference becomes very obvious when the pressure drops to 55 psi.

http://www.fueleconomy.gov/feg/motor...anscript.shtml

Outlook has the high pressure tires. Maximum pressure is 44 psi, not the old 35 psi. So if you are inflating it to 30 psi, you are under inflating it. I think most of the new tires are 44 (my Accord's tires too). I have always inflate them to little over 40 psi, never blew a tire because of over inflation.
It is true tire inflation matters. I have done some experiments and it indeed seems to matter. However more inflation is not always better or safer. For the 19" tires on the Outlook recommended presure is 35PSI if I am not mistaken. While car is in motion tires get warmer, presure increases 2-3PSI sometimes more - depend on outside temperature too. What is better is more inflated tires have less rolling resistance (and you get MPG gain), but on the bad side - you risk having uneaven wear (overinflated tires tend to wear quicker in the middle of the thread), and the worse - there is larger chance to blow an overinflated tire when hitting a pothole or a curb for example. I keep mine at 37 as a "safe" compromise
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post #43 of 46 (permalink) Old 08-30-2008, 01:23 AM
 
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Re: Poor gas mileage and shifting

Quote:
Originally Posted by leobg
It is true tire inflation matters. I have done some experiments and it indeed seems to matter. However more inflation is not always better or safer. For the 19" tires on the Outlook recommended presure is 35PSI if I am not mistaken. While car is in motion tires get warmer, presure increases 2-3PSI sometimes more - depend on outside temperature too. What is better is more inflated tires have less rolling resistance (and you get MPG gain), but on the bad side - you risk having uneaven wear (overinflated tires tend to wear quicker in the middle of the thread), and the worse - there is larger chance to blow an overinflated tire when hitting a pothole or a curb for example. I keep mine at 37 as a "safe" compromise
You are right Leobg, over inflated tires have premature wear along the center portion.

My Accord is '98. I have done 40psi for 10 years. The tire seems to wear OK, pretty evenly.
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post #44 of 46 (permalink) Old 08-30-2008, 09:50 AM
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Re: Poor gas mileage and shifting

The tire pressure is and has been 37PSI since we picked up the Outlook. I really don't want to over inflate because on a trip like we just took, 500 miles one way to Cedar Point in Ohio, I wouldn't want harder tires driving through a rain storm climbing mountains. Every fill up the average was just under 20 MPG. Going to change the oil for the first time and use synthetic and see how that affects it. Not really complaining about the mileage, this is a tank that can move out of it's own way and is a pleasure to drive.

Dave<br />2008 Outlook XR
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post #45 of 46 (permalink) Old 09-01-2008, 12:18 AM
 
Join Date: Aug 2008
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Re: Poor gas mileage and shifting

Quote:
Originally Posted by doropallo
The tire pressure is and has been 37PSI since we picked up the Outlook. I really don't want to over inflate because on a trip like we just took, 500 miles one way to Cedar Point in Ohio, I wouldn't want harder tires driving through a rain storm climbing mountains. Every fill up the average was just under 20 MPG. Going to change the oil for the first time and use synthetic and see how that affects it. Not really complaining about the mileage, this is a tank that can move out of it's own way and is a pleasure to drive.
Good point on the wet traction. I had a scary experience on this. The XR FWD I rented at San Antonio this May broke lose when I hit an sharply curved exit ramp a little too fast (you see, I have driven an Honda Accord for 10 years and not am accustomed to a vehicle that's 1500 lbs heavier). It was raining, the road was wet, but I didn't expect the tires to lose traction so easily. The car nearly hit the guard rail before the wheels regained traction.
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post #46 of 46 (permalink) Old 09-02-2008, 12:46 PM
 
Join Date: Aug 2007
Posts: 3
Re: Poor gas mileage and shifting

Well, I guess I'll throw my 2 cents in on this topic. I was pretty upset too about the mileage not really being anywhere close to the advertised, but it seems to run about the same as most of the posts I read here....AWD version, updated flash program, 20.5 MPG at the very, very best I can do over a 300 mile trip. Sucks around town...13-14 MPG, and the best I can do on the open road is about 22.5 @ 65 MPH. It makes a BIG difference in how fast you drive. 70MPH drags it down to 21MPG pretty quickly.

I had the flash done on the transmission last winter (at about 12,000 miles). I was getting up to 25 MPG out on the road before the programming change. Now it shifts better (not quite as doggy), but it really knocked the gas mileage. By the way, I am taking all of my readings from the DIC.
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