1999 Super Duty mpg problem?
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New User
Joined: Mar 2009
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1999 Super Duty mpg problem?
I have a 99 SD 4x4 extended cab short bed, 5.4, maybe a 3" lift, 285/75/16 tires at's, new engine(reman), etc? I think its a 26 gallon tank and I can only get 240/250 mile to a tank! Im dying here bc my new job requires me to drive 80 miles a day. I know some people drive more, but filling up every other day a spending $60 is getting old. Is there anything I can do to improve the mpg? A friend said to get a chip, he said it improved mpg and gave him more hp....but he has a diesel. Im in need of some opinions.................
Tuned
Joined: May 2008
Posts: 474
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There is nothing wrong with your truck. I have a 05 5.4 and it is not lifted but i just put 287 75 17 good year duratracs on her and my millage went from about 11 to 10 just because of the bigger tires with more agressive rubber. Mine has 410 ls and a true dual exhaust. The best thing u could do is chop the lift and run stock rubber and it will help more then anything. Don't go buy some 20 k pos ricer and think u are saving money because before u burn 20 k worth of gas through your truck you will be dead or u will get a new truck. Gas is almost free now so who cares. Chips are for dip with a beer not for your truck. Every one i know with gas or diesel who chips them has taken them off has they do no good and are a rippoff to boot. By the way my $500 dual exhaust did nothing for mpg but it sounds cool if u like noise and the dual 17 inch ss tips look really cool but it is all gimmicks and realy dosen't run any better. 
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
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From: Stephensville WI
The best thing you can do is to drive your truck like there is an egg (or your left tes...um...family jewel) between your foot and the throttle pedal. You'll gain a few MPG. Never let the engine get above 2500 RPM while accelerating. (It is difficult and very frustrating, but it can be done)
The 3 inch lift is not good for your mileage, but realistically you're not going to get miracle fuel mileage from this truck. 15 MPG is my average from highway driving. It's a big, heavy brute of a truck, which is why you probably purchased it in the first place.
If you want fuel economy, get a micro-clown-car like a Chevy Aveo. Fuel savings alone (based on $2.85 a gallon fuel) would make your car payment.
The 3 inch lift is not good for your mileage, but realistically you're not going to get miracle fuel mileage from this truck. 15 MPG is my average from highway driving. It's a big, heavy brute of a truck, which is why you probably purchased it in the first place.
If you want fuel economy, get a micro-clown-car like a Chevy Aveo. Fuel savings alone (based on $2.85 a gallon fuel) would make your car payment.
New User
Joined: Dec 2009
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The thing about a chip on a gas engine. Gives you a little more power that you can feel. You will tend to use it and not get any better MPG. Plus you need hi-test gas to keep spark knock down. Kinda defeats the purpose if your doing it to save $
Posting Guru
Joined: Jul 2007
Posts: 1,433
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From: Spring Lake
I don't know if this holds true on shortbeds or not (I don't think it does) but a tonneau cover helped me greatly. Remove that lift, use a less aggressive treaded tire, lightest oil possible, and a clean engine!
Some cheap steps to help you out is:
1. Clean your MAF! MAF cleaner available at autozone, and you'll need some q-tips and time
2. Make sure there are no dragging brakes/ rusty u-joints
3. Adjust your cruising speed! I have 3.73 gears and at 65mph I can usually get right about 15mpg. I lose about 2 mpg for every 5mph past that. If you have 4.10's it should be slightly less, I believe less tha 2K on the tach is it's most fuel efficient
4. Now this is extreme, but look into a gear vendors overdrive unit. If you commute 80 a day the $4K might pay off. I have no testimony to how much actual improvement you'll see, but you could get the equivalent of a 3.55 final drive ratio with it (by adding extra RPM without increasing engine RPM)
5. When was the last time you replaced O2 sensors? They can help if the ones you have are shot
I have found my gibson exhaust and K&N air filter didnt do anything for performance or mpg, dont waste your money unless you want a cool sounding truck.
Some cheap steps to help you out is:
1. Clean your MAF! MAF cleaner available at autozone, and you'll need some q-tips and time
2. Make sure there are no dragging brakes/ rusty u-joints
3. Adjust your cruising speed! I have 3.73 gears and at 65mph I can usually get right about 15mpg. I lose about 2 mpg for every 5mph past that. If you have 4.10's it should be slightly less, I believe less tha 2K on the tach is it's most fuel efficient
4. Now this is extreme, but look into a gear vendors overdrive unit. If you commute 80 a day the $4K might pay off. I have no testimony to how much actual improvement you'll see, but you could get the equivalent of a 3.55 final drive ratio with it (by adding extra RPM without increasing engine RPM)
5. When was the last time you replaced O2 sensors? They can help if the ones you have are shot
I have found my gibson exhaust and K&N air filter didnt do anything for performance or mpg, dont waste your money unless you want a cool sounding truck.
