Haha, no no, this isn't for school. I am taking Calc 1 and doing Optimization problems. However, this isn't related to a college question/problem, but rather my own curiosity.
Nothing super complex, just a straight up "if i'm going this speed on the highway, it will produce the best MPG, Ceteris paribus.
I was thinking that if I got different results at different speeds, I could use it to graph a function and maybe use the limits like in the optimization problems to produce a maximum speed for MPG. :cool:
The biggest energy losses in combustion engines come primarily from "unused" energy wasted as heat. Not much you can do about that inefficiency other than buy a hybrid or electric vehicle.
Energy losses that come from things you can control are drag/air resistance, internal engine friction (moving parts), rolling resistance (tire deformation against the road as the tires rotate).
Drag will increase with the square of your velocity (approximately). The slower you go, the less energy you lose to drag.
Gearing: the gear your engine is in will determine the engine speed (RPMs) and resultant internal friction losses. If you are going 60 mph in overdrive, you will have less energy loss than if you are doing 60 in first gear (and blowing up your engine in the process). If you want to take data points to establish a curve, you might want to record RPMs as part of the data. Note: some decrease in engine friction can be achieved with motor oils that have superior lubrication to others (such as some synthetic motor oils, which also reduces engine wear). You will also want to take your data when the engine is at constant (operating) temperature.
Tire pressure affects rolling resistance. If tires are underinflated, they will deform a lot, build up a lot of heat, and eventually destroy the tire (and maybe result in a blowout). They will be wasting energy in the process. Higher tire pressures result in less rolling resistance, so higher pressures result in better gas mileage. Keep tires at (or maybe *slightly* above {a couple of psi?}) recommended tire pressure for best performance.
You will get your best mpg in top gear at low, constant speed (as long as you don't let your engine speed get so slow so as to "bog" your engine down due to bad timing resulting in inefficient fuel burn in the cylinders) with properly inflated tires.
Note: acceleration and braking are times of maximum inefficiency. The harder your acceleration or braking habits, the worse gas mileage you'll get. During acceleration there are big tradeoffs in fuel burn efficiency vs getting up to speed. Braking is pure energy loss (unless you're in a hybrid or electric vehicle that captures some of that energy).
PS In the "old days" it was very important to check plugs, timing, point gap, etc., very regularly. Not so much now -- but at least make sure you have a clean air filter.
Hope that helps.
