Grille Block for City driven Nissan Frontier?
 

I use my 1998 Nissan Frontier 4 cyl./5 speed to deliver pizza with. I drive it city cycle in flat, coastal Florida with a top speed of maybe 50 mph for 1 mile stretches. I am curious to see if I will see a noticeable improvement with aerodynamic changes? I already run 45 psi in the tires and use a few hypermiling techniques (when practical) but still struggle to hit 22mpg. I was considering a grille block for the portion of the grille that is in the front bumper and already have the cardboard and duct tape to try it out. Is it likely to make any quantifiable difference in fuel mileage considering the speeds driven or am I just wasting my time? Also, would wheel skirts make a difference? I can't use smooth wheel covers because the truck has alloy wheels ( and besides I need the brake cooling) so I was considering fabricating a set out of sheet metal as a viable alternative. Lowering the truck could also be considered but it can't be too low because of how it will be used. It uses torsion bars up front so lowering it would be a simple matter of turning the jam nuts out up front and adding lowering blocks out back. This application is much different than most hypermiling vehicles will see as the median average speed the truck sees is likely 35-40mph. The truck also will likely be pulled out of delivery service in a month or so once I can finish my Metro enough to go on the road, so I don't really want to spend a lot on this. It's more of a proof of concept than anything. I also don't have a Scangauge yet as my budget is going towards the OBD I Metro project so my only way to quantify it will be by tracking mileage and fuel fill.

The grill block is easy to try out, so why not do it and see what gives ?

Obviously, the slower you drive, the less effect the aerodynamic mods will have. They really come into play at around 40 mph - though any cyclist will know there's a huge difference between 15mph and 20mph ;)

An air dam is another easy mod, and rather effective on trucks.

Brake cooling isn't really an issue.
If you're ecodriving, you should already be using them sparingly anyway.

In order to understand how the truck is driven, you need to see it in terms of a sort of brute force economics. On a busy day the amount of deliveries taken depends on speed. How rapidly you get to a delivery and back determines just how many deliveries and thus tips you will make. On a busy day then it pays to drive quickly as the additional tips offset the savings in fuel costs. On a slow day though, when you are not likely to come back to more deliveries it pays to save on fuel costs. On both kinds of days certain hypermiling techniques can be employed to save on fuel and time. I time my traffic lights, use hills to coast down to red lights, plan my routes, etc. as well as reading traffic to adjust to the best possible way to attack each circumstance. There is never any good reason to speed up to a red light only to be stuck behind 10 other cars. I have even tried pulse and glide but found it impractical for my needs.

As far as braking goes, during busy months it is not uncommon for me to run through a set of front brake pads in as little as 2 months or 6k miles. During those times I end up late braking a lot because it makes economic sense. After all, a set of brake pads is only $20. Right now it is unusually slow-probably due to a U-6 unemployment figure of 20%+ in my county. Thus I go through a set of front brakes in about 5 months. In fact it is so slow now that I will start looking for another business to work in in the next few weeks.

i think weight reduction will be important. when you do high speed long distance travle weight is less important, as it will basically act as a flywheel, but on slow, stop/go travel you'll have to accelerate all the mass of the vehicle over and over again and than wear out breaks to bring it to a halt again so, the more weight you can use the less fuel and breakpads you'll use. so considder what you can. evaluate the risk of leaving the spare tire home, or if with a little tinkering perhaps the passneger seat can we made to be swapped in and out with little effort perhaps...