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Discussion Starter #1
Guys I am getting 16.5 mpg on the highway, yeah I know its terrible. I have 4:10 gears, is this the cause? 5 speed 4 wheel drive stock rims but little bigger tires, not much over stock. 100 fuel plate but star wheel is not cranked anymore for this reason. :banghead::banghead:
 

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how fast? speed can be the difference between 14 and 25mpg...
 

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Discussion Starter #4 (Edited)
Sorry I forgot to post that. I do not go over 61 mph but my gps says 64 mph at about 2050rpm. I accounted for the tires. I do about 400 miles on about 26 gallons, I would say maybe 30-40 miles more because of the tires pushing me to the 16.5 mpg. I am trying to be conservative...
 

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Discussion Starter #6
More and more money. Thats the problem I have. My paint is shot, 260,000 miles, and I have put a ton of money in it already. Thanks guys for the feed back
 

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I have 4.10's with 285's. Adding 7% to mileage for the tires I can get about 17-18 with mostly highway. With the colder weather it's probably closer to what you're getting.
Bumping my timing is on my long list of things to do. You might see if you can find someone with the tools that would be willing to lend a hand, shouldn't be too expensive in that case.
 

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Discussion Starter #9 (Edited)

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Discussion Starter #10
I have 4.10's with 285's. Adding 7% to mileage for the tires I can get about 17-18 with mostly highway. With the colder weather it's probably closer to what you're getting.
Bumping my timing is on my long list of things to do. You might see if you can find someone with the tools that would be willing to lend a hand, shouldn't be too expensive in that case.
I have 305 tires so what percent would you add? i also live now in San Luis Obispo, which is pretty warm.
 

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Just plug it in here. :thumbsup:
Tire size calculator

I'm not familiar with 305's. 305/70/16 appears to be what your talking about? If so then 7.7%. It says mine's actually 7.8%
When I got mine it had 255/85's I believe. The guy said it was about 7% so that's what I used and the new tires were supposed to be about the same. It says they were actually 8.5% though. :confused013:
 

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Discussion Starter #12
Well I was pretty close, at 8% it says 16.5 mpg, frustrating. I was thinking of changing gears to 3:73's, how fast are you doing at 2000 rpm, and how is towing, people with 3:55's how are yours towing and at 2000 rpm?
 

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At 2000rpm I think it reads about 63-64, so probably around 68 actual. Pretty close to what this calculator says it should be http://www.f-body.org/gears/
This is with an auto also, remember.

I don't really tow that often but moving this summer it was fine pulling a horse trailer full of junk. Fine with a bobcat also. More worried about my bumper falling off than not being able to pull it. Really need a receiver hitch. :hehe:


Do you consistently get this kind of mileage? It should be better during the summer.
 

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Discussion Starter #14
Well when i got the truck, a little over a year ago, I remember checking once and I got 19 mpg but I was doing 2100 rpm. My dad payed so I was doing a little faster.:hehe: But since then I did all thats in my sig, except there was a fuel plate but I do not remember which one. It was a 60 hp plate but I don't know the number. I imagine it getting 17.5 maybe in the summer. Its hard to tell cause in the summer I am always hooked up to a trailer.
 

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I think I'd look into adjusting your timing. It sounds like some tuning might be helpful too. If you got 19 at a higher rpm before (assuming you usually keep it at 2000?) then the truck is clearly capable of more.
 

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I have 4.10's with 285's. Adding 7% to mileage for the tires I can get about 17-18 with mostly highway. With the colder weather it's probably closer to what you're getting.
Bumping my timing is on my long list of things to do. You might see if you can find someone with the tools that would be willing to lend a hand, shouldn't be too expensive in that case.
i also have 285's w 4.10's. i can see the 17-18 in a straight line only w/cruise on. mine is at about 16-16.5 all the time. i'm pretty happy with that...don't think you'll see mileage improvement with the timing change, just performance.
 

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i bought my truck with 305s what size did a stock 97 come with?
 

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Discussion Starter #18
Thanks guys for the information. :thumbsup:
 
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