Should you spend $20,000 on a brand new lunchbox that promises 28MPG* (always an estimate) when you can get it out of the car you own? I’ll let you in a little secret – I did it in a supercar – so the answer is a resounding NO.
No one has ever believed this until I’ve taken them for a ride and shown them. No, I am not a powerful wizard, and if I were, I wouldn’t tell you now would I? That would come with loads of responsibility, like stopping or reversing catastrophes, car accidents and such. No, just a guy who likes a little challenge. When I purchased my 2003 Corvette Z06 a few years ago, I obviously wasn’t out to save a buck, and in particular, wasn’t worried about fuel mileage. It didn’t take long before I noticed that my overall average most of the time hovered around 20MPG. This was strange because cars in this bracket tend to be in the teens at best. I knew I could push that up, but there are limits. I set out to see just how far up the scale I could bring it.
I need to get something out of the way. Modern gas sippers equipped with the ECO-Tech blah blah aren’t actually well built for saving fuel. There’s a pesky little thing called drag coefficient that most manufacturers don’t bother worrying too much with. In a nutshell, it’s the measure of drag (resistance) proportional to the density of air and the square of the relative speed of the vehicle. It’s calculated and represented as a number like .45, where the lower the number, the more aerodynamically efficient the vehicle is. A Volkswagen Beetle for instance, is .48 – a mid-eighties Jetta? .36 – and my Corvette in Stock configuration is a .29. This is almost meaningless below 55mph, but then things change. A vehicle with a .29 doesn’t start to have an adverse reaction to speed until around 70mph, but a vehicle with a .40 will use more power to maintain 70mph than the .29. What this means is that not only is the .29 able to move faster, it’s using less relative power, covering ground faster, therefore using less fuel. This is not always true, some engines are just inefficient, but that’s for another article. Another important factor is weight. A 2013 Nissan Maxima weighs 3,568lbs, and a 2003 Corvette Z06 comes in at 3,118. Which means it has to use less of it’s power to move and maintain a speed based on the laws of motion (Newton).
Asleep yet? There’s more but we need to get on with the blood and guts here.
One of the first things I did after the purchase was drive it down the east coast from Charleston, South Carolina, deep into Florida. After a meandering around a week or so, I was ready to head home. I reset the trip computer, filled her up and into the wind I went. I’m good at getting good fuel mileage. Slow starts, coasting down hills etc (details later) … but I wasn’t really thinking about that as I’d be almost entirely on the interstate. I went from Daytona Beach, Florida to Atlanta, Georgia in 6hrs 13m (do the math, yeah it was fast) and the car managed 27.5 on the overall average. Not bad, but I wanted an impressive combined city and highway mileage. So I made a few modifications, and set my route to work as a benchmark. There were two ways to get there – one mostly interstate and one all back roads – so I simply went one way and came back the other. The interstate way was 16.9 miles with 4 stop signs and 5 red light intersections – 16.3 miles coming back on all back roads with average speeds of 45mph, 3 stop signs and 4 red light intersections, and to mention when I arrived at my place of employment – I slowed to a stop before returning to the road. Overall MPG? 28.5 – After modifications? 30.2
Granted, I am not under the illusion that the computer is precise – in fact the fuel mileage displays in all vehicles are based on an estimate the computer makes, and they tend to be optimistic. That 30.2 is likely closer to 28… I am yet to go as far as putting a fuel cell in the trunk and actually measuring fuel consumption manually, which is the scientific way. But based on that, I went from 20mpg in stock configuration, to 27.5 on an interstate trip, to 30+ with slight modification = about 30% increase in fuel efficiency, by driving style alone and another 5% or so modifying. I’m not alone here – Doug Pelmear (look him up) has a Mustang he’s modified that has been measured at 110MPG, seriously. It’s a 400 horsepower engine, just like mine. As stated, I’ve modified my Corvette, but nothing as radical as Doug. I lowered it, thereby decreasing it’s drag coefficient, and added an active ram air system which produces more power at high speeds, which lowers how much specific power is consumed maintaining a high rate of speed. I have also done a few other secret things along with a custom ECM (computer) program, which I also did myself, so I realistically have much more than the stock 405hp. However, the only meaningful fuel gains by modifying that vehicle was a consequence of the decreased aerodynamic drag. I’m not telling you to lower your car, but it certainly doesn’t hurt. One thing that is a huge advantage in the Corvette is unique to the Z06 – a full underbelly. It is smooth under the car, because turbulence is your enemy. This is something that will not affect the ride of your car, and any custom fiberglass or aluminium fabrication shop can assist you with. (Always consult automotive experts, modifying automobiles yourself or a random fabricator is dangerous and can cause serious injury or death! And possibly destroy your car!) This will be largely negligible though, until you change the way you drive.
Da Da DUUUM! Finally! John, you’re really long winded!
I know. I will now define what I mean by “It’s not what you drive but how you drive it“. There are exceptions, as I said before. Most engines produced before the 1990’s are by nature just have a poor fuel consumption rate because of the way the older fuel injection/carburetion systems, gear ratios and aerodynamic properties are configured. There are even technical considerations as seemingly innocuous as the parasitic loss of power in the driveline (transmission, CV axles, etc…) from the use of inferior metals and loose tolerances. Also, you should know a manual transmission vehicle will always be more fuel efficient than an automatic, because of how power is delivered, and the gears are locked as opposed to a torque converter in an automatic, which always allows some slippage to occur, and automatics tend to have less favorable gear ratios. To perfect all of the things I’ve mentioned plus everything else that factors into a good balance of power, aerodynamics and fuel economy, one would be required to pay a psychotic attention to detail in the design process. Generally, high performance cars have everything they need for spectacular fuel mileage but can’t for their immense power, and the opposite is true of most consumer passenger vehicles. They lack any of the things which will make the little engine useful at all. A small engine in a heavy car has to use more of it’s power than does a light car. You will be hard pressed to find a modern passenger vehicle less than 3,200lbs! That’s heavy. But the average supercar is around 3,000lbs (most anything that can boast a sub 4 second 0-60mph and/or over $75,000 – so buy used! I did, I only look stupid). Rarely have the two worlds ever met, it’s not economically viable to the manufacturers, apparently, and they’re confident you won’t notice. Well I know better so… on to how to save fuel!
Your foot is not that heavy
No one wants to be the guy who leave a red light and takes until the next light to reach the speed limit. Well, some of you do (you know who you are). You don’t have to, think of the pedal as 0-100% – many cars are programmed for their idle to set the throttle at 5-9%, give yourself about 15% of the pedal to accelerate. Be safe, if you’re merging into traffic – for crying out loud – match the speed before throwing yourself at the mercy of the guy cruising in the right lane eating a hamburger while texting and trying to get his Bluetooth to connect, your life or another insurance claim is not worth a few pennies of fuel. But be easy, once you’ve reached the speed limit, hills are your friend. Give yourself +/-5mph of flexibility on normal roads. If you’re going 45mph down a hill and taking your foot off the pedal doesn’t do anything, do it, coast. If you speed up, don’t worry. Up a hill, refrain from digging in to keep that 45mph, remember the 20% rule and if you find yourself going 39mph when you reach the peak, that’s fine – chances are you’re about to go back down. Now, is it unsafe and sometimes illegal to slow too much – or speed (obviously), which is why I have that 5mph rule, it’s considerate to other drivers, legal, and most of all, efficient.
What’s that up there?
Anticipate stopping, try to avoid it. Look ahead, scan the road, and if you see a red light 300ft ahead, lift off the throttle and begin coasting – the hope here is that the light will change and if there’s already traffic ahead of you, they can get moving before you get there. We come back to Newton’s laws of motion for this, it’s all about conserving energy. Every time you accelerate and then hit your brakes, you are literally scrubbing away the energy it took to get to that speed, and releasing it as heat into your brake rotors. An object in motion tends to stay in motion, and you want to maintain as much momentum as you can at all times. If you’re on the interstate the same applies, if you are approaching a vehicle slower than you, as long as it’s is safe to do so, pass them, do not lift from or press the throttle, nor hit the brakes unnecessarily. Again, I have to say do all of this in a safe way, don’t spend all of your time worrying about it because you’ll create a weird situation in which you can defeat it all by driving too slowly or dangerously – like swerving – all of which wastes fuel, it’s almost as bad as idling. Speaking of which, if you have a way you go every day somewhere and know a punishing red light which always stays red for a thousand years, keep your foot on the brake, slip it into neutral or park (some cars require park to restart) and turn off your engine! Please be considerate and be ready to start it back up, especially if you can see the perpendicular light turn yellow for your queue! Keep up with traffic and within the law, but you’ll find the more you think about these tips the more they’ll make sense and find yourself becoming more aware of your surroundings, and finding that on any trip less than 100 miles or so, you won’t save any time going 90mph, maybe a minute or two – do the math. A good rule of thumb for efficient speeds is 65mph. Back in the seventies when the national speed limit was set at 55mph, it made sense because most of the cars on the road at that time shared their drag coefficient with a brick, but you can bet your car will do fine at 65mph, but almost all cars begin experiencing unnecessary drag around 70mph or so, and no matter the case – always observe local traffic laws!
Sure, but being a powerful wizard, I can’t reveal all of my secrets. Following these few tips, you’ll slow down (but still get there on time), save money (for sure), and maybe have a little fun (if you like to challenge yourself). Drag coefficient aside, I took a 2013 Toyota Camry (25mpg city, 35mpg highway estimate) on a short average (about 20 miles mostly city) and peaked at 37MPG today, I could get more, and with a few mechanical modifications, could realistically squeeze out 10-15% additional. My 1996 S-10 4.3L V6 with 300,000 miles gets 25MPG+ with me behind the wheel in stock configuration. You don’t have to take my word for it, but try it, you’ll see a difference immediately. There is a magical mile per hour in every vehicle, the Corvette’s is 78 – the S-10’s is 62, what’s yours?