V6 Gas Millage - help please

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Asim

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Guys:

Someone must know something.

Been to two seperate dealers and nothing.

2000 LS 6 sport. 12 miles to the gallon.

In Ontario we have an emissions program and it ran super clean. Changed the plugs, fuel filter, air filter is a K&N, all the usual stuff. Tire pressure is right.

Took it to 2 dealers for a run through all their tests and they say the car runs perfectly.

I am a mix of hwy and city driving and my last car was a 95 Z28 with 365 horse and that car got better millage and I drove it way harder.

Full tank, no more than 215 miles. What the heck is going on?

I met two guys that have the same car and they get like 25 MPG. One even has a bad miss and he gets about that same. They all agree that my car is in the best shape, but the fuel ecomony is outrageous.
 
I have the V8. After I changed the VC gaskets and cleaned the plugs and coils, my gas mileage went way up. I was getting around 270 miles per tank. I now get 340 or better per tank.
 
I can understand plugs and coil, but don't see the connection between valve cover gaskets and gas mileage (?)

I just had my 2003 LS6 to the dealer for a 30k service and was told there was a firmware update for the transmission. Could it be that your trans is staying in low gears making high rpm and consequently low gas mileage ?

i was getting about 22 mpg with a 2000 LS8 in my normal driving; now have a 2003 LS6 and have been getting 20 mpg :(. i ran a bottle of Techron cleaner in 1 tank of gas - maybe I'll wait a few thousand miles and try another ... Regardless, I think you should be getting around 20 mpg ...
 
It's not the gaskets directly causing the problem, it's what happens when they leak. The leaking VC gaskets allow oil to get into the plug wells, which causes problems with the coils, which in turn leads to poor performance and bad mileage. Replacing the gasket stopped the leaks; cleaning up the plugs and coils was what solved the problem.
 
If the powertrain is functioning normally, it's time to check things that resist the car's movement. Start with the brakes. Check the pads and make sure you don't have a stuck caliper, and make sure that the parking brake is fully releasing. Also check the alignment--do you have any uneven wear on the tires?

12mpg seems way low for a V6. I know some of the V8 guys get that in town, but unless you're idling and sitting in traffic a lot, you should be doing significantly better than that. The worst mileage I got in my '06 V8 still got me close to 300 miles

Of course, this all assumes that the problem isn't a loose nut behind the wheel... :D

BTW, a tranny reflash is only appropriate for an automatic transmission.
 
Do you have a fuel leak somewhere ?

Are you carrying to much stuff in your trunk ? (if you have it full of subs, serves you right :D)

Sooner - Thanks. Does the 6 cylinder use the same coils as the 8 ? Didn't they stop making the standard trans in 2001 ?
 
PaulJK said:
Sooner - Thanks. Does the 6 cylinder use the same coils as the 8 ? Didn't they stop making the standard trans in 2001 ?
Click to expand...
I'm pretty sure they use different coils, but a leaky valve cover gasket could kill them just the same. AFAIK, however, the V6 never had the VCG leak issues that the V8s did.

They made the 5-speed manual transmission from '00 through '02; it was dropped in the '03 redesign. IIRC, there were only about 1200 of them built in total.
 
How cold is it in Ontario now? Does your mileage improve during warmer (not hot) weather? My V8 LS get's an average of 340-360 miles per tank all year round... but my V6 Taurus SHO gets ~320 in the summer... 210 in the winter... per tank!!!

My buddy moved his IAT sensor from the airbox to a coolant hose which made the PCM think the air temp was warmer and leaned out the mix a bit.
 
The millage I am calculating simply by how many miles I get on one tank - only 94 Oct. I drive the car like a gentlemen. I've been past 5000 rmp once ever. Past 4000 maybe once a month when I get stuck and need to muscle out of a tight spot. Like I say, same driving conditions and I got better millage on my modified 95 Z28.

Are you guys referring to the rubber boots that are in the spark plug valley as a possible source?

My back passanger side rim gets more brake dust then all the rest, but the car coasts freely on its own, so I can't imagine how much drag it's causing.

Trunk has 1 12' and some thin plywood and carpet decorating.

Please keep thinking / responding. This is the one thing that is stopping from avoiding autotrader......
 
If two service departments tell you the car runs perfectly and the car doesn't seem to miss, I can't imagine that misfires could possibly be bad enough to cut MPG in HALF! Since leaky valve cover gaskets and the related damage to the coils is common on 2000's, this certainly needs to be checked. However, I don't think it's the root of your MPG problem and I don't have a solution. As an aside, theoretically the 2000 auto transmission is "sealed for life", with no flush required.
 
First, you are not benefitting anything by running 94 octane. Stick with 91 or as close as you can get it.

How long have you had the car? Maybe want to try and disconnect the battery for half a day and then let the PCM relearn your driving strategies.
 
bill5 said:
As an aside, theoretically the 2000 auto transmission is "sealed for life", with no flush required.
Click to expand...

Really? Never heard of that before. My service manual has fluid changer intervals for my 2000 V8.
 
my owners manual for 2000 v8 sport also says tranny fluid change intervals of 30 thousand miles
 
Hey guys, is there any more info on this I have the exact same problem, my 2000 V6 barely gets 300 miles to the tank. And I know I can get better then that, I just replaced the VC gaskets, plugs and coils. Whats the word??
Thanks,
Elisha
 
I have a 2000 V6 and I'm getting around 18 in the city and this is in rush hour. On the highway I'm cruising at 70 and getting about 23 mpg. I have to use the high octane. I used regular unleaded and it knocked and pinged so bad I thought I was tearing up the motor.
 
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