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Gas Mileage
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My last four fill-ups are below:
448.7 mi. 22.255 gal. 20.16 mpg
442.6 mi. 21.940 gal. 20.17 mpg
487.5 mi. 23.402 gal. 20.83 mpg
450.2 mi. 21.188 gal. 21.24 mpg
My truck actually has better range between fill-ups than my wife's Buick LeSabre. Of course it also has a 25 gallon tank to her 17 gallon tank, but still... I'm impressed with GM trucks!
I can only guess as the '99's and 00's start breaking in, people will be reporting 22's and 23's since their engines are more efficient.
-powerisfun
these 13-15 MPG quotes from using 93 octane? How
about an ethanol mix?
The mpg figures you quoted are close to what I get with the V-10 and 4.30, and I get the benefit of the extra power. If you get the 3.73 axle ratio with the V-10, your mpg should improve quite a bit. I don't think you will be disappointed, especially with the increased V-10 power for the 2000 model.
Anyway to cut a long story short they reckon that a tonneau cover reduced drag by between 20 & 30%. This all came down to the fact that the air is prevented from entering the truck bed and becoming even more turbulent. Not sure if I believe the figures, but this must translate into a significant increase in economy.
I would greatly appreciate it if you would post
where you read that article. It sounds very interesting. Thanks.
-Tim (powerisfun)
Geez, you don't half like making me work don't you. I was fairly convinved that I read it on the web, but I couldn't remember where. Anyway, after an exhaustive search I found it.
http://mars.acnet.wnec.edu/~ehaffner/did.htm
I was slightly wrong on the reduction, it comes out at a 12% reduction, but still significant. The 30% saving was the new design they propose.
They also do some comparisons with tailgate down, removed etc. Fairly interesting (for a university study).
have a hard tonneau cover on my truck and I'm really happy with the mileage I'm getting (I have a '98 GMC Sierra x-cab Z71, 5.7L, 3.73 rear, 9900 miles, and I'm averaging over 20.5 on my last 4 tankfuls).
If you read the website listed in the above
response by andy_jordan, it shows research into
wind drag on pickups. According to them, leaving the tailgate down reduces drag by something like
3%. Oddly enough, removing the tailgate or installing one of those nets in place of the tailgate disrupts the flow and causes an actual
increase in the drag. A tonneau cover decreases drag by 11.8%.
-Tim (powerisfun)
With the taigate down, the separation point occurs at the top of the cab. This means the pressure drag occurs over the the back window, and the front of the bed, which is a larger area than just the tailgate.
Pressure drag is called such because the pressure on the back of the vehicle is lower than that on the front of the vehicle (because of the more turbulent flow, from separation).
Now, that study was done on Ford production trucks, no aftermarket. Lift kits, tires, toolboxes, etc, can certainly change things.
I am sure exact results will vary depending on any number of factors, but the airflow pictures are quite interesting.
tailgate, now I won't bother and will look into a bed cover. I drive a '99 Dodge QC 4x4,AT, 5.9L with the 3.55 axle ratio and 11300 miles. I have kept track of the mileage on every fillup, the worst was 13mpg towing a 2000 lb tent trailer (I think the gas was oxygenated because I got the same lousy mpg when I filled up at that same station again and I was able to get 15.8mpg on the same trip from other fillups). The best mpg has been 16.8 twice, living in AZ these figures are always with the AC on. These figures are with the tailgate up and a K&N filter, I will be putting the paper filter back in for a run or two on my 300 mile test route in the next couple of months as I want to see if it makes any difference now with the engine a little more broken in (the K&N filter went in at 7000 miles and I don't have mpg on that route for the paper filter). I will post the results.
My 92 F-250HD 4x4 with the 351 and 3.55 only got 14-15 on the hwy. That's about what the new Ford V-10 with the 3.73 gets and the new V-10 has a lot more power. Same mpg with significantly more power. I'd consider that an improvement. Maybe someday they will make a gas engine that will get close to 20mpg and can effectively move a 7,000 pound truck, but for now, they call it a diesel.
Yawl must be driving too slow.....
Thanks
Good luck whatever you decide.
-powerisfun
-powerisfun
The hesitation also doesn't sound right. My '98 has no hesitation at all and the '99's and 00's that I test drove also had no hesitation. I would definitely take it in for that.
-powerisfun
Is that mileage for city or highway or a mixture (if so, what percentage highway), and what axle ratio? If it's mostly city, I'd say that sounds about right. But if it's mostly highway, unless your axle ratio is 4.10, I'd say your highway mileage should be near 20 (or even above) as long as you're not too heavy on the pedal. If the plugs and filter don't help, here's a list of things I would check (some or all of these may be obvious, but a reminder can't hurt):
PCV valve (just replace it for around $3 and 2
minutes work)
EGR valve
spark plug wires (are they original? if so, they
probably need replaced. Replace them with
low-resistance wires)
tires inflated to at least 35 lbs.? (mine say 44
lbs. max so I keep them at 38 lbs. cold)
wheel alignment
catalytic converter clogged? (that happened to me
on a jeep cherokee with the 2.8L V6. I
couldn't get better than 16 mpg and it seemed
really under-powered so I sold it. The guy
that bought it changed the cat. conv. and said
it had tons more power and was getting
over 20 mpg)
fluid level in rear differential
dirty engine oil?
-powerisfun
I inflated the tires correctly, but I'll definitely change the PCV valve, and the wires. I think I'll hold off on the catalytic converter until I'm really convinced that there is a problem. (Them things ain't cheap!)
I noticed a power/response difference when I changed the plugs and the filter, so I'm hoping that this tank of gas will show an improvement in mileage as well.
Anyways, thanks for your tips, and I'll keep you posted.
i don't think the fuel costs will be as bad as you think.