Last post on Dec 14, 2009 at 2:08 PM
You are in the Chevrolet Cobalt
What is this discussion about?
Chevrolet Cobalt, Engine, Coupe, Sedan
#24 of 27 Re: I'm moving next week to home, First.... [pa356228]
Oct 01, 2009 (7:25 am)
The drop in mileage is not necessarily meaningful to me. If no engine lights are on and th engine runs well there probably isn't anything actually wrong.
First you had a very low tire, so low it may have damaged the sidewall. The tire store would have warned you if they thought it had happened. That tire hurt the mileage reading you had been getting.
Second we have switched to winter gasoline. It is a higher volatility cut of the distillate. That gives better starting for cold engines when incoming air is colder than summertime, but it hurts fuel mileage. Also you may have been getting gas that has more alcohol in it. The alcohol hurts your fuel mileage. Try using only name brand gas when you can and you'll probably see a difference.
Third, I have the tires in my Cobalt at 36 instead of the recommended 30. That helps mileage. It hurts the ride some. But especially on a longer highway trip the gas mileage increase will be meaningful.
Fourth, I don't think GM recommends changing gas line filter unless there's a problem with fuel pressure. If you have 120,000 miles and occasionally buy gas from the cheapie stations that aren't brand stations, you might change it just in case you got some gunk somewhere. But most stations have filters inline or actually on the hose that filter out "stuff." Save the money for the fuel filter for something else.
Fifth, the only thing I'd chance wasting a little money on would be a 12 ounce size bottle of Techron fuel system additive, not the injector cleaner which is cheaper. It's at Walmart or Advance Auto or others at about $5.95. I think one newspaper ad this week had two for $7.95, the alleged regular price. I'd put that in like that bottle says when the tank is fairly low, while you're ready to pump gas in, then fill the tank. It _might_ clean your injectors and fuel system. The gasolines usually keep injectors clean. Another option is to fill up with something like Shell's Premium V fuel WHEN your tank is about half full already so you're mixing regular and premium and ending up with about Plus grade octance; you don't need highest octane, but the cleaners might help instead of using Techron additive. There are supposed to be extra additives in the higher grades of fuel; it might, might clean up injectors if there is anything crud on them. Other people probably have their preference of additives but mine has been Techron through the years. I only use it maybe twice a year because I pick up a bottle when I see it on sale at one of the auto parts box stores.
#25 of 27 First, Third and Fifth...
Oct 02, 2009 (12:30 am)
First one: The tire repair shop, had to take out a nail out of one of the treads, didn't go thru the sidewall. Luckly, it didn't puntion the tire. So far the psi is holding 32.
Third one: Will it be better to set all the tires at 36psi? On Thursday, of next week, I'll be hauling up to 400 lbs on a 443.5 miles drive. Will it still be safe enough? According to your cobalt, at 36 psi, what is your Cobalt mpg aveage?
and Fifth one: According to the driver's manual, my Cobalt should only use 87 brands, Will it hurt the engine if I use 89 brands (or Premium)? And one more question, sorry about asking too much questions, btw. Does Techron fuel system additive works? Since you been using it for years, Does it cleans the whole fuel system and what else does it do?
#26 of 27 Re: First, Third and Fifth... [pa356228]
Oct 02, 2009 (5:53 am)
The tire pressure varies 1 pound/sq in with every 10 degrees up or down Fahrenheit. At typical outside temps now of 60 degrees in mornings my gauge shows 35 or 36. It used to be 37-38 when mornings were warmer. I find the dash gauge shows one tire higher. Don't trust the tire sensors; get your own $1 gauge and set the tires yourself when cold. 36 should be good; pressure will increase some with tires warming up and especially with a load.
The Techron was an early additive package by Chevron sold at stations. BMW long ago when gasolines weren't carrying good enough additives in some cases recommended Techron. It was the same additives used by Chevron in their gasolines. Since then government intervention required better additives in all gasolines, including regular. I still use Techron rather than other over-the-counter brands just because I feel it works. A Cincinnati car repair talk show guy recommended it for cleaning injectors up until he went off the air a year ago. He owns a body shop and major independent repair place in a high end part of the city. He was a graduate of the local vocation school for the county. He knows his stuff.
It also cleans and protects the fuel gauge sensor potentiometer metals against deteriorating from sulfur in gasoline. GM had a few gauges that would corrode from that and give erratic readings. In the past decade when I would put it in and drive the car, the car seemed to run better after half an hour's driving. I believed it did clean up what some gasolines left on injectors. Then I used to buy cheapest gas and mix brands about half and half with known name brands. Now I buy Kroger's gas, Mobile/Exxon, and Shell. Rarely anything else. I don't notice as much effect after putting it in the last couple of years. I consider it throwaway money spent for the additive. If I didn't use it I would probably occasionally spend extra money and run a couple of fillups of premium Shell/Texaco, Mobile, or Marathon thinking I was cleaning up the fuel system with the supposed better additive package in the premium. (We don't have Chevron in this area anymore.) Since the car doesn't need premium, I would only do that for a couple of fills--the first fill had 87 octane gas mixed with premium while the second would increase octane above 89 for the mixture.
A little philosophy here: most stations mix premium and regular to get the Plus grade. So I'd rather just add some gallons of premium where I know I'm getting 100% additives and gas rather than trust their computerized mixing ratio and just buy Plus.
The Techron Fuel System Cleaner supposedly does more for the whole system; an identical looking bottle is called Techron Injector Cleaner and I believe it contains less additives overall because it's usually cheaper.
My personalized advice would be add a 12 oz bottle of TEchron to a low tank, fill with premium. Drive it down to half a tank and refill with quality brand premium. Then use regular of a good brand. Do that for your trip. Occasionally put in a few gallons of premium to fill your tank. Otherwise use quality brand regular to avoid alcohol in higher percentages which cuts gas mileage.
#27 of 27 idleing problems
Dec 14, 2009 (2:08 pm)
i have an 06 chevy cobalt ls and i have the same problems as you when i stop at a light, or turn the air or the defrost on the car wants to idle bad just wondering if you have found the problem if so i really need to know ive changed the map sensor and a few other thing still hasn't solved my problems the car is getting to the point were it will stall itself out thanks...