It's summer, and I'm drivin' distance again: cottage, mom and dad's, that kind of thing.



Obviously, everyone, including me, is affected by gas prices, so, here's the tips that the interweb provides for us, plus the bits I know.



First off, let me give you the deets on my car. Technically, it's rated at an EPA (so, US gallons, the little gallons) 24mpg city, 30mpg highway. That is, approximately, 9.8L/100km city, 7.1L/100km highway.



This, however, is what I got over the weekend:



Distance travelled

620 km

385.27 miles



Fuel Amount

35 litres

9.25 US gallons

7.7 Imperial gallons



Fuel Economy

5.65 litres per 100 km

41.66 miles per US gallon

50.04 miles per Imperial gallon



So, how the hell does THAT happen?



Well, first, I do expect to lose a little economy when I buy new tires: what I have on are super-efficient tires, hard compound. Lousy for handling, great for fuel economy.



Second, tire pressure. I tend to run about 1PSI higher than manufacturer's spec. Acura says 32psi in the front, 34psi in the back, I run 34psi front, 35psi back. The general rule is, for every pound of pressure under spec, per tire, you lose about 2% fuel economy. So, you have four tires, under-inflated by about 3PSI each? that's a potential lose of 24% fuel economy. Ouch. I don't know if you actually gain 2% per pound over, and you can speed-wear your tires by over-inflating too much, but if you get just a little extra in, you harden the tires up, get better economy.



Empty the trunk. Really. The current estimate is that if you clean a mere 10 pounds (lbs) of junk out of your car: trash, cd cases for cd's you never listen to, change, loose stuff, camping gear you use once a year, you'll gain back 10-20% of your fuel economy. Weight costs money. And extra weight costs you at the pump.



I drive a stick. Learn to drive a standard properly, you can save money, by always having the transmission in the place you want it, the engine working at the proper RPM for efficiency.



Air flow. A lot of cars, in fac,t most cars, restrict air-flow into and out of the engine to keep it quiet, so they can advertise based upon decibel levels in the car. seriously, who gives a shit? As long as you don't have a coffee can exhaust (that doesn't help), get a k&amp;n filter on, get more air going into the engine, remove the restrictive air-box (which is what I did) and buy a cold air intake kit. Power's a nice byproduct, but this will get you more economy.



Tune-ups. OIL. Oil changes save you fuel. Fuel filters. Spark plugs. Make sure it's all working properly, and is changed as per schedule. This will save you gas, and give you power back.



driving style.



Most people lose fuel economy on driving style. Idling at the corner store. Warming your car up for ten minutes in winter. Driving three blocks when you could walk. Red-light Rabbit. Highway Warrior.



I'm not saying you can't enjoy driving: I love to drive, and I push my car occasionally. But. if you're driving less than a couple of kilometers... don't drive unless you don't have a choice. The emissions systems and engine aren't warmed up in short hops, so you're hurting the emissions systems: they don't do anything until they're warmed up, and the engine's running hard and harsh until it's properly warmed up too. That's generally about 10km of driving. Driving less distance than that? You're killing fuel economy.



Racing to the red light? Yeah, that costs you. As much as a 60% loss of fuel economy. Slow down, you'll still get there. You'll save your brakes and transmission, too.



On the highway, well, find the sweet spot. Every car has one. the speed at which the car runs best and most efficiently. It's not, as the enviros would like you to believe, 90km/h. It depends on your gear ratios, how many gears you have, your over drive gear, and what RPM works best for your car. For me, on the highway, I get my best mileage around 108km/h.



HOWEVER.



I've been avoiding the highway. My entire trip to mom and dad's this weekend was secondary roads. Long, stop-light-free, two-way traffic, single-lane roads with 80km/h limits. If you plan your trip, you'll find very often that while you go slower on those roads, they're more direct and you actually drive less distance, negating the speed/time advantage you'd assume you get on the highway by going quicker. For example, the distance to my mom and dad's place, by highway, is about 280km. With a coffee stop, or two, it takes about three hours. The car zips along at about 110km/h and 3200rpm in 5th gear. In comparison, if I take secondary roads, the distance is about 235km. I set the cruise around 92km/h, 2700rpm in 5th gear, and it takes me just about... three hours. And I get better mileage on secondary roads because there's less aerodynamic resistance, and I'm running at lower RPM's. THe time I 'save' at higher speed is negated completely by the extra 40km or so I have to drive when I use the highway.



Passing. If someone's doing 2km/h slower than you, but maintaining that speed consistenly, stay behind 'em, drop your own speed. It won't cost you any real time. If, however, their speed is really inconsistent (70km/h one minute, 90km/h the next, then back down to 75km/h) pass 'em quickly, and set your cruise again around the high-side of their speed zone. You'll stay ahead then.



Air Conditioning vs Open windows. My experience is, under 100km/h, open the windows. You don't lose enough aerodynamics to justify the A/C. Over 100km/h? Turn on the A/C, close the windows. On the highway, you're always better with the windows up.



I like to drive late at night too, if I can. Fewer people on the road, and most of 'em have someplace to get to. You can maintain speed. THis doesn't mean you have to drive after midnight, but, avoid rush-hours, either at your starting point, or your destination. It slows you down, you end up stopping and starting, and it costs you at the pump (and the brake shop!)



So, I didn't drive particularly slow, but I do drive SMART. That's what more people need to do. Just by making a few changes, I shaved 2L/100km off what the EPA thinks my car can do, and much, much more than that off an aggressive driver, who might have saved him or herself five minutes on a three hour trip by passing a lot, and taking the highway.



For comparison, I got 5.65L/100km in a mixed-circuit (city/highway). The Toyota Prius hybrid (the fuel economy benchmark at the moment) gets 4.5L/100km city, 4.7L/100km highway. IF you drive it right. I got passed by a prius popping along at 140km/h, I'm willing to bet he wasn't getting better than 10L/100km at that speed. Driving style is as important as what you drive.



Any way you look at it, the EPA says I should have spent $70 on gas this weekend, and I spent about $45 instead. I can live with that.