I'll be a fun project for some

[SilveradoMike]

Hello, Im Mike. I am a contracted parcel carrier driving my own vehicle and paying my own fuel. My vehicle is a '99 Chevy Silverado with a 4.8l v8 and a 5 speed manual trans with 4wd.
I'm looking to get into hypermiling as much as is reasonable for my situation. Like no engine off coasting (to much cargo weight for that) and shutting off engine while idleing more then a minute or so (restarting about 75 times a day would kill my starter and charging systems). So a little more detail on the truck. Its a bone stock truck in the single cab long bed configuration. It has an A.R.E. Commercial +4" shell on it (shell is 4" taller then cab non tapered) The truck currently has LT245/75/16 E rated tires on it but the door tag calls for LT 265/75/16 C rated tires. After some reseach I found that going down a weight rating but up one size will net a loss of 4lbs per tire. And I found that my rear axle has 3.73 gear ratio which is great for pulling my 700-1500 lb load daily but terrible for highway speedsy.I drive ~200-350 miles per day (including commute) 90% of my daily mileage is rural windy roadd. A few things are unchangeable in my scenario tbe truck the load the miles. The ine that that can be changed is slight aero mods (I was thinking a deflector from my cab to the shell) And the nut behind the wheel can be changed. My fuel current fuel mileage numbers are slightly off due to wrong tire size but for the last 3 months I've averaged between 17-18.5 mpg. Id like to push to the 25ish or higher range. I plan on replacing my tires with the correct size next week along with ordering a scan gauge from here. Any suggestions to consider? Thanks everyone.

[Frank Lee]

Your fe is as I'd expect. It's fun to shoot for 25 but without more engine off time I don't see how that'll happen.

I'd do an e-fan swap, partial or adjustable grille block, deeper air dam, perhaps a collapsible boat-tail as seen on semi-trailers now. Of course you'll find more options if you dig around here.

[SilveradoMike]

Thanks for the reply and suggestions. I did pickup a Scangauge 2 today for 160 locally, pretty sweet so far. Only driven about 10 miles with it but average is 16.8 for the day. Im going to look into the things you suggested. Do you think there would be any benefit to making an aero piece to cover the height between my cab and camper?

[Frank Lee]

I think it depends on if the leading edges of the cap have a decent radius or not. Either way, I'd wager the potential benefit to be <1mpg.

[t vago]

Welcome! Can you do any under-hood mods? Warm-air intake? Grille block?

[SilveradoMike]

Front of the camper is totally square to the cab. About 4" taller then cab all the way across the roof line. The sides gently taper down to the same width of the cab at the bottom edge of the side windows. Really... less then 1mpg.... hmm... As far as vehicle mods where is the most improvment to be had? I could do a belly pan but I would only make it out of steel. So Im not sure if the areo saving would over come the weight gain.

[SilveradoMike]

Originally Posted by t vago

Welcome! Can you do any under-hood mods? Warm-air intake? Grille block?

I can do under hood stuff as long as it is CA smog legal. (Stupid Commiefornia) I did do a cheap cold air intake already. It seemed to gain about 1.3 mpg. Its already paid for it self.

[t vago]

Well, seeing as how it sounds like you're just starting out into ecomodding, I'd say that you should continue with your existing plan of replacing your tires, buying that ScanGauge, and adjusting the steering wheel/gas pedal actuator. After your tires are replaced, you can inflate them 5 psig over what is recommended for your truck (just don't go over the max rated inflation pressure on the tire sidewalls, please).

I have found that all by their little lonesome, driving style adjustments net me about 15% or so over EPA combination ratings.

[SilveradoMike]

Thanks for the suggestions. I guess I should give some of my back ground. I was a automobile technician before I became a mobile logistics technician. So my mechanical aptitude/handy ness is pretty high. But usually Ive modded cars for power and seen minimal at best mpg gain. But I would also did a hp mod and then used that extra hp. Ive always had this thought/theroy that if you had more hp/tq in a usable rpm range you would net higher mpg. But usally you need more fuel to make more power so maybe not. Does this hold any ground? Ive been looking at rv style cams for my motor. A corvette cam would also work but they are more high rpm power not low end tq like Im looking for.

[wmjinman]

If replacing the camper shell with one flush with (same height as) the top of the cab is "in the cards", that would both streamline it AND reduce the frontal area. If not, I'd probably try to streamline the front above the cab. If it was me, I'd get some 2" styrofoam & carve it with saws, files & sandpaper until I had a nice "ramp" transitioning from the top of the windshield to the top of the camper, gradually curving so it's parallel with the camper top by the time it gets to it. And I'd try to have it continue down the sides, rounding off that front corner, coming up as far forward as you can without interfering with opening your door. You see that idea with commercial trucks & motorhome conversions sometimes. Then I'd slap it on with duct tape & do some "A-B-A testing" with the ScanGauge.

But I agree with Frank Lee - you'll probably see less than 1 MPG out of it. However - as MetroMPG says, "There's no "magic bullet", just magic buckshot". Do lots of little things, and you'll get the effect of doing a big thing. As long as there was ANY gains at all from your A-B-A testing, I'd say, make it permanent.

Does your truck have cruise control? That is EXTREMELY helpful for A-B-A testing. The ScanGauge, if utilized sufficiently, will be your AWESOME powerful tool in figuring out what works and what doesn't. I didn't start using the "trip" feature until recently, nor the throttle position display and/or engine load display either, but those can really be informative.

One, maybe "too obvious" thing you'll see here a lot is speed. If you're racing around going over the speed limit all the time, you're burning a lot of extra gas. One of the more enlightening things I did with my ScanGauge was went out & tested my MPG at different speeds - all the way from 80 mph down to 35 mph in 5 mph increments. Clearly, you can't get away with going 35 mph on a freeway, but if you're on a street or back road that lets you, and you happen to know (from your ScanGauge testing) that 40 mph is your best MPG speed, why not go 40 for a mile or two if it "works"?

Another biggie is the brakes. I just HATE hitting the brake pedal, because in my mind, I can see the gas just evaporating every time I do it. Someone else on here has a quote that goes something like, "Braking = turning gas into heat and brake dust". If you have hills on your route, instead of maintaining speed (by feeding it more gas) going up the hill, try holding the accelerator steady and letting the speed bleed off, then regain it going down the other side. That trick can help.

There is a mountain of stuff on this site, and it's not always too easy to find what you're looking for immediately. So if you don't see what you're looking for, ask, and one of the guys here will probably have your answer for you.

Oh, and WELCOME to the site!!!!!
Bill