Bad gas mileage

[cometcougar]

This is probably way too general, but I figured it couldn't hurt to ask. My Comet with 144 ci 6 cylinder and 2 speed automatic does not get good gas mileage - somewhere around 14-15 miles per gallon, but it runs great. I bought the car with a rebuilt engine, but I'm thinking the carburetor might be the place to start looking for the cause of the bad mileage. Do any of you have any suggestions or advice?

[redfalken]

Hard to tell what might be going on but you should probably be able to do better than that. I usually get 17 with my 200 and a 2bbl. I would start with the basics. Make sure it's tuned properly (put in a Pertronix unit if you don't like to mess with points and it may add a mile or 2 to the gallon), check the timing, adjust the carb, make sure the plugs aren't fouled (and are gapped properly) and check the tires for proper pressure.

After that is all done, get a tank of really good gas and spend the time until your next tank trying to avoid quick starts and stops. Most people don't think of hard braking as wasting energy but it can really add up so don't waste the energy from your gas as heat in your brake shoes. Let off the gas earlier when you come to lights or stop signs.

Other than that, make sure your brakes aren't dragging, check for leaks in your gas tank or lines, don't idle too much when you can avoid it, and put a rare earth magnet on your main fuel line so the gas molecules will be lined up as they enter the carb (just kidding on that one!).

[drowndrat]

Hard to tell what might be going on but you should probably be able to do better than that. I usually get 17 with my 200 and a 2bbl. I would start with the basics. Make sure it's tuned properly (put in a Pertronix unit if you don't like to mess with points and it may add a mile or 2 to the gallon), check the timing, adjust the carb, make sure the plugs aren't fouled (and are gapped properly) and check the tires for proper pressure.

After that is all done, get a tank of really good gas and spend the time until your next tank trying to avoid quick starts and stops. Most people don't think of hard braking as wasting energy but it can really add up so don't waste the energy from your gas as heat in your brake shoes. Let off the gas earlier when you come to lights or stop signs.

Other than that, make sure your brakes aren't dragging, check for leaks in your gas tank or lines, don't idle too much when you can avoid it, and put a rare earth magnet on your main fuel line so the gas molecules will be lined up as they enter the carb (just kidding on that one!).

Have you,or do you who anybody has used that "Tornado" air deal?the one you simply place in the carburator,or throttle body?

[redfalken]

Sounds too good to be true and you know what that usually means. Here's an article on these gadgets and the final paragraph. Thanks to Jeff W for telling me about it.

http://www.popularmechanics.com/automotive/new_cars/1802932.html

"THE MORAL OF THE STORY - We've tested nowhere near all of the fuel-saver gadgets on the market, and I'm sure purveyors of others will be waiting in our lobby soon. But not one of the items we tested worked. At all. There's no ignoring the laws of physics, people. Your vehicle already burns over 99 percent of the fuel you pay for. Less than 1 percent is squandered as partially burned hydrocarbons and carbon monoxide before the exhaust hits the catalytic converter for the last laundering. Even if one of these miracle gadgets could make the combustion process 100 percent complete, the improvement in mileage resulting would be 1 percent. Any device that claims quantum-level increases needs to be examined with considerable skepticism."

[Toolfool]

If the car runs good and the plugs are a tan color. (see http://www.theultralightplace.com/sparkplugs.htm )

6 cyl cars normally has high gear ratio.

I would look at gear ratio, possibly trying some larger rear tires that you can barrow from someone. Beware that lowering the ratio may reduce preformance.

I have hear that electronic ignition can help.

My Ranchero gets between 22 and 24 on the hi way it has a c-4, 2.80 rear end and 195-14 tires and its a 200 with electronics.

My 2cents....
John

[Sedanman]

I suggest doing a compression test as well. Not all rebuilt engines are alike - the supposedly rebuilt '68 200 in my '64 gets about 14mpg, although I do have a bad exhaust leak which might be heating up the carb and making it run rich.

[drowndrat]

It all comes down to this..........Keep your engine in tune,correct tire pressure,and clean oil in the pan.Samethings we've ALL been taught.

[cometcougar]

Thanks for all the ideas and advice everyone. I really appreciate it. Just thought I'd give an update - I just got a pertronix for it, and hope to put that in this weekend along with new distributor cap and rotor just for good measure. Also put on a fresh new air filter element. Carb seems to be adjusted well, and I haven't found any leaks along the line, which is good. I'm also going to pull the plugs and just make sure they look good, and gap them, and do the compression check while I'm at it.

I checked the tire pressure and made sure the brakes had proper adjustment too. I am really liking how accessible everything on this car is to work on! My daughter got her license last Tuesday, and has been putting more miles on it than I am now. Now I've decided it will get a dual master cylinder very soon too.

Thanks again, and of course let me know if you think of any other ideas for getting my gas mileage higher.

[Jeff W]

My latest Popular Mechanics talks about gas mileage. One thing they mentioned was the accuracy if the odometer. Many cars are off a few percent, some motorcycles as much as ten percent. Our older cars, with all the goofing around with tire size, gear ratio's and the like may be off even more. This inaccuracy in the actual distance traveled would really skew the final calculation. If you or a friend has a good GPS that measures mileage, you may want to see how your odometer compares to the accuracy of Billion dollar satellite.

In other words, your gas mileage may not be as poor as you calculate.

[melo-yelo]

Have you,or do you who anybody has used that "Tornado" air deal?the one you simply place in the carburator,or throttle body?
I have not used the tornado, but just the other day was at a local auto parts store waiting for my turn and was reading a copy of a Consumer report magazine and they reported that the tornado device made no change what so ever in gas mileage or performance. They did lab testing and real world tests, 100 and 250 mile tests, both injected and carburated engines.

[cometcougar]

Just thought I'd share a little success story - I installed the pertronix this past weekend, and today was the first time I had a chance to really get it out on the open road. I can't believe the difference in power. Whereas before this car was sluggish and really labored up hills, it now feels like a brand new car and runs smoother. I haven't gone far enough yet to see if I'll have an improvement in gas mileage, but the increase in power and performance alone makes it worthwhile.

[redfalken]

Great job! It's always really satisfying when you can get such dramatic results for not much money. Are you using your stock coil? And did you gap your points wider to .40-.45?

Let us know when you fill up next how your mileage changed.