Emissions and old gas

Sinister CO

Member
Jul 15, 2005
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Highlands Ranch, Colorado
After recently getting my car going again I faced our lovely emissions testing here in CO. I probably had close to half a tank of old gas in it so I just topped it off thinking it might be okay. Yeah, not so much.

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So that was fun. I'd never had any problems before so I drained almost all of the gas out and put fresh stuff in the old girl. Ah, much better.

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The gal that ran it through the second time couldn't believe that old gas would make that much of a difference. Oh well, lesson learned.
 
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~JM~

Wrinkled Member
Oct 31, 2007
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Fresh fuel, fresh oil change, a hot engine & a hot cat converter, will help.
 

NY Twin Turbo

All the good stuff.....Times 2.
Dec 10, 2014
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It would seem you should copy these results into another thread in General Buick Turbo Tech.

It may help others understand how important it is to have good clean new fuel in their tank. There seems to be a lot of newbies that post up questions about problems after letting their cars sit for a long time. They don't seem to take it seriously how important good gas is until after they have had problems. This may help.
 

turbo chris1970

Engine bay
Aug 29, 2011
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philly PA
Wow great idea to post that ,especially us buick guys are a small group compared to all the other car guys and gals out there in the hobby and we need to help each other out with good advice to keep our cars on the road they are GM legends after all
 

Roc87

11 Second V6
May 25, 2001
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Wonder if thats why my HC's were up? At least half the gas in my tank was over a year old, it did 399 of 200 at idle where 2 years ago it did 11! Won't ever run old gas while trying to pass again
 

b4black

Well-Known Member
May 24, 2001
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Aurora, IL
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Old fuel won't effect your emissions like that. Old fuel looses the light ends, making it harder to start and maybe hesitate when accelerating, but topping off with fresh will easily correct that.

This car failed big time on the first pass. I suspect it was something other than the fuel - like the catalytic converter wasn't hot enough. Or it needed a good, long heating up to burn off the junk that collected on it while sitting.
 

Sinister CO

Member
Jul 15, 2005
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Highlands Ranch, Colorado
Wonder if thats why my HC's were up? At least half the gas in my tank was over a year old, it did 399 of 200 at idle where 2 years ago it did 11! Won't ever run old gas while trying to pass again
Yeah, you can see that the HC was high on my test. Literally the only thing I did was the fresh gas. Same drive to the testing facility. I got right in both times so there wasn't any big cool down period.

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No disintegrations

Active Member
Dec 27, 2015
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the old gas has less energy contained in it because the lighter components are gone. The combustion chambers and cat run colder because of that.
 
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