V8 Guys Highest MPG

Something is up with mine.....went from 25-28 on the highway to 21 on the highway after installation of a Magnaflow Cat-Back.
 
Fastbird said:
Something is up with mine.....went from 25-28 on the highway to 21 on the highway after installation of a Magnaflow Cat-Back.
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Thats probably about right. I am guessing you bought the exhaust for its sound. Slight changes with intake and exhaust can definately change the factory "stock" ratings in regards to mileage.
 
Fla02LS said:
Thats probably about right. I am guessing you bought the exhaust for its sound. Slight changes with intake and exhaust can definately change the factory "stock" ratings in regards to mileage.
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This is semi-true. I'll agree that many cars sold have "tuned" exhaust systems. However, I've owned quite a few cars and nearly every one got an exhaust system, and NEVER have I seen a drop in fuel economy with an addition of a cat-back exhaust that's less restrictive than the OEM system. Especially not a drop in economy to the tune of 5+ MPG.
 
Fastbird said:
This is semi-true. I'll agree that many cars sold have "tuned" exhaust systems. However, I've owned quite a few cars and nearly every one got an exhaust system, and NEVER have I seen a drop in fuel economy with an addition of a cat-back exhaust that's less restrictive than the OEM system. Especially not a drop in economy to the tune of 5+ MPG.
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Makes you wanna take a second look at that "less restrictive" aspect of the magnaflow for the LS. Its sounds better but the overall big picture might just not be as good as it seems. On big power cars like the T/A its a different story because those stock setups were awful, and if when you modified the intake then the exhaust needed to be modded accordingly. The LS might actually have a very well engineered exhaust.
 
Fla02LS said:
Makes you wanna take a second look at that "less restrictive" aspect of the magnaflow for the LS. Its sounds better but the overall big picture might just not be as good as it seems. On big power cars like the T/A its a different story because those stock setups were awful, and if when you modified the intake then the exhaust needed to be modded accordingly. The LS might actually have a very well engineered exhaust.
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True.......but the power gains people have seen on the dyno (~30 RWHP with various Cat-backs and CAI) don't lie.

Another perspective........wasn't a major contributing factor to the 03+ LS's increased power rating (284 or something like that up from 252) the newly revised exhaust system???
 
Fastbird said:
True.......but the power gains people have seen on the dyno (~30 RWHP with various Cat-backs and CAI) don't lie.

Another perspective........wasn't a major contributing factor to the 03+ LS's increased power rating (284 or something like that up from 252) the newly revised exhaust system???
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Yep, that and the VVT. Intake was also modified.
 
z1069 said:
Maybe some new people can post their findings.


;)
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Best of mine was a 370 mile trip that included the mountains of Western Maryland. Speeds from 55 to 80 @ 25.0 by the computer and 24.9 by hand. No AC, just the windows closed and the vent on (it was cool out).
 
Oddly enough, today on the return trip from PA, the car showed a calculated mileage range between 390-415 miles and the MPG average varied between about 25-30.6 MPG.

I have a feeling that the problem was the cars adaptive capabilities coupled with almost solely stop and go traffic for the past few weeks.
 
I just got my 2000 LS V8 last week. The first day I had it, I took it to Chicago and back (200 mi round trip), and averaged 24.9 mpg on the computer. Then, a few days later, I went back again and got 25.5.

After those trips, I installed a cone-shaped K&N filter right on to the MAF housing (eliminating the airbox entirely), and I drove home to New Jersey (~780 miles), and I got 27.1 mpg on the computer.

I'm not positive if the filter helped, since I didnt try a 700+ mile trip on the airbox, but the car sounds better and it seems to have helped. Not bad for 30 bucks, and I hate airboxes anyway!

I'm not overly impressed with the city mileage, but the highway mileage is not too shabby on these beauties.
 
I managed 389 miles on the last tank, had a serious tailwind on my way to work that day (about a 130mile drive).

Did the math on a 66 litre fillup and it worked out to 26mpg. Pretty good for a 2000 3.9 w/3.58 gears :).

Usually I get about 21mpg though on average driving, combo of highway and ruralways.
 
Well, on the drive back from the honeymoon I decided to "max endurance" the LS and see what I got. Cruise at the speed limit (65-70 depending on state) and we filled up at..........

438 miles. And still showing 30 to empty on the computer. Ended up getting right at 26 MPG as calculated by hand. Should have been higher but we stopped like 5 times during that tank of gas. Can't complain.

Put 4K miles on the car in just under two weeks though. :(
 
94 mark 5 speed. 28.7 mpg 1763 mile average speed 68.9 hand held. drove to colorado springs and back in 27 hrs. last hour was in la la land should have stopped but get home itts set in. dumb but servived. jd
 
I've been getting a consistent 21.5-22 with about 80% highway and a heavy foot on the backroads that other 20% of the time.

By the way, my first 3 tanks of gas when i got the car were regular 87 octane (because i didn't know any better), and since I've switched to premium 93, my mileage has not changed one iota.
 
Higher octane gas doesn't help (or hurt) fuel milage.

It's all about the combustion point. With high compression engines (10.9:1 IIRC) you can't run 87 and expect the engine to last.
 
OK, I seem to be on the lower end of the spectrum too! I have a 2002 LS V8 with 34K. The best I have average is 21 on the highway, and a consistent 16 - 17 average per tank with a 50/50 mix of city/highway driving. I have been very easy on the pedal too! The sticker from the window showed 17/25, but I have yet to see it.

Also, my AC Filter shows 24% left. From reading through this thread, how do I go about changing it? I seen a mention of it, but not how too??

Thanks,
Steve
 
KC_Steve said:
OK, I seem to be on the lower end of the spectrum too! I have a 2002 LS V8 with 34K. The best I have average is 21 on the highway, and a consistent 16 - 17 average per tank with a 50/50 mix of city/highway driving. I have been very easy on the pedal too! The sticker from the window showed 17/25, but I have yet to see it.

Also, my AC Filter shows 24% left. From reading through this thread, how do I go about changing it? I seen a mention of it, but not how too??

Thanks,
Steve
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your mpg sound about correct, the LS does not do well in the city. however, it is fun to drive in the city

i am averaging 20.2 mpg with 20/80 city/high way mix.

ac filter has nothing to do with your mpg, do a search for "cabin filter"
 
I remember reading something in this thread (at least I think I do) about someone who rarely if ever went over 2,000rpm (which is going VERY easy on the gas)... and now I'm up .1 to a whopping 15.9 mpg!
 
I most often drive my 2002 V8 with 30,000 miles. I'm getting 21-22 mpg with all highway driving and a very sad 14-15 in city driving.
 
I ran out of town on business today. I reset my fuel economy once I hit the highway. Ran about 100 miles straight highway, 65-80mph, some cruize on and some off, stopped, then did a few city miles, stopped at a ATM, stopped to eat, then drove some back roads, 25-55mph throu some small towns and three more stops including a gas stop, then all highway back, 65-75mph, some with cruize on. Total of 240miles. 24.3mpg when I pulled in my driveway. I didn't pay attention to the up and down as I drove.

I've got the Magna-Flow exhaust and the new aluminum LSK Intake with the open filter. Just turned 40k.

I can honestly say there is little difference in mileage with those mods. So close that without running the identical trip back to back to compare, its hard to say the mileage difference. If I had to guess I'd say its slightly better.
 
48,000 miles. 60 miles jont from Santa Fe to Albuquerque. All stock 01 LS8 except for drilled air box. 33.4 MPG @ 65/70 MPH.
 
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