TERRIBLE gas mileage in my 4.3, what do you think?
02-01-2007, 03:29 PM
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TERRIBLE gas mileage in my 4.3, what do you think?
I just picked up a single cab 2003 chevrolet silverado witht eh 4.3 v6. It is an automatic with 38k miles. I am wondering what kind of mileage you are getting in these trucks. It was a certified gm used vehicle when i got it about a month ago. I am only getting about 12-13 mpg in the city and not much better on the highway. When the truck is on the highway and when in cruise control at about 70 (completely unloaded) it sometimes has to drop out of overdrive to maintain speed on hills. The only modifications to the truck are 265/75 bfg ko's. The tires are not excessively big nor do the rub or anything so im almost positive that this is not the culprit entirely. There is not an ses light on either..........what do you think????
02-01-2007, 03:41 PM
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Do you know what rear end you have? My CC w/ the 5.3 has 3.23's and even with the extra torque of the V8, it would downshift going up hills after I put the 285's on it.
Ny old RCSB 4.3L was a complete dog from a perf. standpoint, but the worst mileage I ever got was probably 15 or 16. I wouldn't think that the tires would have made that big of a difference, but if you are constantly in and out of 2nd and 3rd gear getting around, I wouldn't doubt that 12-13mpg would be the result.
Ny old RCSB 4.3L was a complete dog from a perf. standpoint, but the worst mileage I ever got was probably 15 or 16. I wouldn't think that the tires would have made that big of a difference, but if you are constantly in and out of 2nd and 3rd gear getting around, I wouldn't doubt that 12-13mpg would be the result.
02-01-2007, 04:33 PM
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bfgs are very heavy tires. depending how far you wana go from a performance stand point, id say either get some smaller tires, get some lower gears, or just wait and get a 6.0. like moddoo said that is a lot of truck too.
PS: SLOW DOWN TAKE IT EASY
PS: SLOW DOWN TAKE IT EASY
02-01-2007, 06:11 PM
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The OE goodyear 235/70/16 weighed in at 30 lbs and gives 691 revolutions per mile. The 265/75/16 BFGOODRICH allterrain ko weighed in at 51lbs and rotated 656 times per mile. Taking into effect that the bfgs rotate 95% the distance that the oe tires rotated in one mile, the 12.5mpg that im getting translates into 13.16 actual mpg. Would the 21 extra pounds on each tire really hurt gas mileage that much? I try to stay out of it as much as possible.
Does anyone have a 4.3 automatic regular cab with bfg's? If so what is you mileage, That would answer all of my questions in one lol
Does anyone have a 4.3 automatic regular cab with bfg's? If so what is you mileage, That would answer all of my questions in one lol
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02-01-2007, 07:40 PM
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Originally Posted by nightrunner
i have a 99 rcsb 4.3 ( dont drive anymore, for sale) and i cant say what mileage i got because my gas gauge didnt work and i never fixed it but i got about 350 miles to the tank if anyone knows how to figure it
I am seeing around 300 miles to the tank in the city and a little less than 350 on the highway. Also another question i had, does anyones oil pressure guage fluctuate? I notice it more when it is cold but the guage fluctuates up and down about +-5 to 10 pounds when idleing. Is this normal? I have never had a vehicle do this...
02-01-2007, 07:47 PM
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My old man has an 01 1/2 ton with a 4.3 and he had the same story as you. He replaced something in the distributor on a GM techs advise and he immediately went to 17 mpg in town. He has a reg. cab though. I never asked him what he replaced (and he did it himself) but the tech said it was a common problem on the 4.3 engine.
Russ
Russ
02-02-2007, 12:32 AM
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Make sure that the truck is properly tuned first.
Your tires are not helping you a bit. The truck is trying to turn 20 extra pounds on every corner. That is alot of differene. Recipricating mass is a weird thing. When you hang that much more weight out on the ends of axles, it takes it's toll on the powerplant, not to mention shocks and springs as well. It takes alot more power to spin that extra weight. If you have a 3.43, you will be now geared much higher than that, and further kill your power.
Also, your speedo has to be off by at least 5mph. You will be registering less miles, because the larger tire covers more ground for each revolution. So you are not getting a good MPG reading because of that. On a truck with a smaller engine like that, I would not go any taller than the stock height. Maybe a little wider, but not bigger. The larger tires are taking the mechanical advantage away from the six lunger.
Your tires are not helping you a bit. The truck is trying to turn 20 extra pounds on every corner. That is alot of differene. Recipricating mass is a weird thing. When you hang that much more weight out on the ends of axles, it takes it's toll on the powerplant, not to mention shocks and springs as well. It takes alot more power to spin that extra weight. If you have a 3.43, you will be now geared much higher than that, and further kill your power.
Also, your speedo has to be off by at least 5mph. You will be registering less miles, because the larger tire covers more ground for each revolution. So you are not getting a good MPG reading because of that. On a truck with a smaller engine like that, I would not go any taller than the stock height. Maybe a little wider, but not bigger. The larger tires are taking the mechanical advantage away from the six lunger.