40 mpg in 04 V8. What are you getting out of yours?

LS4me said:
TWICE (in 1993) I got 50mpg in a '92 Civic. That was with the cruise set at ~67mph and mostly level freeway. That was between northern San Diego county and LAX with only about 15 miles of the 315 miles non-freeway. The A/C was off and windows up. I did the calculations by hand so know they were right. I only achieved this twice; most of the time the mpg was in the upper 30's. We had a 1977 Plymouth Arrow that got consistently in the low 30's!

All the additives in today's fuel really kills performance.
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Nice, at least someone still does calculation by hand. I don't care if the computer says you are getting 5 mpg or 50 mpg. You really wanna know what your car does, hand calculate. It's the only mileage I will believe in.
 
40 MPG sounds fanciful for a V8 LS.

My best consistent performance with my '06 V8 on highway driving was about 28 MPG, driving at 70 mph alone, in summer, with no significant loads in the car.

However, I figure that if I tried running at, say, 55 mph, I could get a significantly better result... but certainly not 40 MPG. Maybe mid-30s at best; I'll have to try it sometime.

As for city driving, I get anywhere between 13 and 18 MPG, depending on the conditions. I saw 20+ a few times, but it's rare and during mostly exceptionally clear night driving, no traffic and all greens.
 
I live in a very mountainous state, so I never get the best. However, on this 155 mile trip I have to regularly take I usually go around 85-90 the whole way and get 21 or 22, depending if going east or west due to elevation changes.

Not bad.
 
Try this. If in the city, keep it no higher than 4th gear under 40 mph.
 
BigRigLS said:
drop 2 ounces of acetone in a full tank and see what happens.
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I tried that on a 1996 Tahoe. The first tank I saw a 2MPG increase, the next 10 tanks mileage was normal. Since the 2MPG increase was for one tank only, it indicates that there was no actual improvement in mileage. I've tried a lot of the things out there that are supposed to save fuel and have an apparent sound theory behind it, and found that most of them do not work.

So far, the only changes I've come across that consistently alter mileage is running electric fans in place of an engine driven fan, tire changes, internal engine changes, programming changes and sensor changes. Anything that makes it easier for the engine to turn, or reduces the effort needed to move the vehicle, has worked to improve fuel efficiency. Fuel additives can only help to a point by making sure the fuel injectors are as clean as they can be as this results in better fuel atomization. Beyond that, nothing. I'm not saying that there isn't anything, just that nothing I've tried so far has worked outside what I show here that has.
 
Telco said:
I tried that on a 1996 Tahoe. The first tank I saw a 2MPG increase, the next 10 tanks mileage was normal. Since the 2MPG increase was for one tank only, it indicates that there was no actual improvement in mileage. I've tried a lot of the things out there that are supposed to save fuel and have an apparent sound theory behind it, and found that most of them do not work.

So far, the only changes I've come across that consistently alter mileage is running electric fans in place of an engine driven fan, tire changes, internal engine changes, programming changes and sensor changes. Anything that makes it easier for the engine to turn, or reduces the effort needed to move the vehicle, has worked to improve fuel efficiency. Fuel additives can only help to a point by making sure the fuel injectors are as clean as they can be as this results in better fuel atomization. Beyond that, nothing. I'm not saying that there isn't anything, just that nothing I've tried so far has worked outside what I show here that has.
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That's all the acetone would really be for that one tank, a fuel additive.
 
I drive 2 hours to work about 90% interstate i will get anywhere between 24-28, in town i get about 16, and i don't punch it at every red light.
 
BigRigLS said:
That's all the acetone would really be for that one tank, a fuel additive.
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Heh heh... I also tried a water vapor thing that was supposed to help by using expanding steam to take up some of the space in the combustion chamber that the fuel/air mix would normally take, which would also require less fuel since there would be less air in the cylinder. That didn't even get me a measurable difference on one tank even though I tried it for 10 tanks worth.
 
These were taken after a 35 mile trip though the city with some traffic lights and speeds from 35 to 45 mph. When I started from the house the reading was 18.6 mpg. It was night time and a medium drizzle. The computer was last reset about half a tank before the most recent fill up. I have just replaced the silencer after reading about some heat soak issues. I wonder if that has an effect on fuel mileage in very hot conditions.

I have 2 shots here to show both fuel readouts. I will take another trip and post those readings. I'm still learning to drive my LS for fuel economy and I also just lowered tire pressure from 35 psi to 30.
 
You can click the link in my sig to see how closely I track mpg. To 1nastyLS, how fast were you going over this 40+mpg trip, and what were the miles and gallons used? I must have missed that in the thread. If you're going by the trip computer reading, it can be garbage. Ya gotta fill up and do the math.

My best was about 29.5mpg over a 465mi stretch (15.74 gal). Next best was 28.6 over 439mi. If I set the cruise at 50mph on level ground I have no doubt I could reach 33-35mpg, but where can you do that for a whole tank? 40 real mpg over the whole tank is BS. I'm not interested in what you got for "a good stretch".
 
Robot said:
These were taken after a 35 mile trip though the city with some traffic lights and speeds from 35 to 45 mph. When I started from the house the reading was 18.6 mpg. It was night time and a medium drizzle. The computer was last reset about half a tank before the most recent fill up. I have just replaced the silencer after reading about some heat soak issues. I wonder if that has an effect on fuel mileage in very hot conditions.

I have 2 shots here to show both fuel readouts. I will take another trip and post those readings. I'm still learning to drive my LS for fuel economy and I also just lowered tire pressure from 35 psi to 30.
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You should actually increase the tire pressure for mileage.
 
svt98t said:
You should actually increase the tire pressure for mileage.
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I did that over the winter months. With my setup having a slight toe-out, I have to lower the cold pressure to compensate for the temperature rise here. My car is twitchy enough and the hot pressure would make it a bit much because the cops are watching for deuces big time here.

Before you ask, the toe-out is necessary so I don't have to cross my arms when turning because I couldn't find a quicker steering gear.
 
Thread jacker ;)

Ranchero50 said:
Actually to the OP, your cold air intake is really just screwing up your tune. You should never, ever, ever mount your MAF sensor differently vs. the OEM package without a custom tune. Using a different diameter tubing or even having an excessive bend before the sensor will cause the airflow through the pipe to be different vs. the factory expected setup. On my old '93 Mustang with the Paxton I could rotate the MAF housing in the duct work and see the A/F curve change on my A/F meter.

Here's a pic of my CAI. All I wanted to do was get rid of the leaking baffle pipe.

DSC01426.jpg


And I'm with the other guys, until you do an actual mileage check fill up to fill up and miles / gallons of fuel, you have no idea what mileage you are getting.
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Your intake idea caught my eye so i followed suit today...

Aaaand i give up! there's a picture of it on the FB lvc page if someone would like to put it on here for me.. I have the hardest time resizing photos to fit on here :(
 
I get 24 in town but my in town driving is like highway all stock but have k&n filter, royal purple oil, 134,000 miles

But I live in the outer part of the city, only on road i n town and speed limit is 45 mph, and I all was round up so going into town just put the cruse on 55mph (round to the next even number then go 5 over that, and that's the equation )

Yes I get a lot of tickets
 
I see the OP hasn't provided visual (DTE readout) proof. More vaporware!
 
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