Go back to COMG- The Cruze Owner's Maintenance Guide
I wrote this up for another forum I'm on and figured it would be a good basic write-up for this community as well.
How to Get Better Fuel Economy
So I've had my Cruze Eco for about a month and a half now and I've made it a game to see how high of a fuel economy I can get. I drive 75%-90% city driving and manage 36-40mpg on a car rated for 28mpg in-town. I've picked up a few tricks, techniques, and methods along the way which, in light of the expected gas prices this summer, might benefit some of you who want to save a few bucks.
As of the time of writing, I was able to (with my Cruze Eco MT) manage 39.8MPG in my last tank of gas with 80% city driving, and my current tank of gas shows 46.1MPG on the DIC with 170 miles driven at 75% city driving, which is consistently 1.5-2.0mpg too optimistic. I expect 43-44mpg at the next fill-up. Consider that the car is rated for 28mpg city, 42mpg highway. These methods work.
Lets start with the simple stuff; mechanical. The behavioral techniques I'll mention later will be useless if your car has mechanical issues.
A. Tire pressure/Tires. This should be obvious, but some people are too lazy or they just forget. I'm guilty of this. I spent 3 months chasing down a condition in which my car pulled ever so slightly to the right. I only realized when I put snow tires on that one of the tires was low. Facepalm. If you're buying new tires, narrower tires are better than wider tires for fuel economy. Lower rolling resistance, less air drag.
Tire's should be inflated according to the manufacturer suggestion. I say suggestion because its just that; a suggestion. This is a number that is provided for a "best compromise" situation. A lower tire pressure will soften the ride and provide better dry traction, but will cause more heat due to rolling resistance and reduce fuel economy. Too low of a tire pressure can result in catastrophic failure. A higher tire pressure will stiffen the ride and may compromise dry traction, but will improve fuel economy as much as 3-4mpg.
Tires can be safely inflated to their maximum sidewall pressure without any danger of catastrophic failure, as this is set by the manufacturer of the tire. Reports on cleanmpg.com forums indicate that tire life is also greatly extended when tires are inflated beyond the car manufacturer's suggested pressure. Most people who inflate to the sidewall recommended pressure end up replacing their tires due to dry rot well past the tire's warranty mileage, not due to balding, loss of tread depth, or uneven tire wear. It is up to you to determine what the best pressure is for your tires based on the information provided in this section.
B. Mechanical maintenance. This isn't so obvious, but it should be considered. If your fuel economy flat out sucks, something is wrong. Spark plugs/wires and O2 sensors do go bad after a while and need to be replaced. MAF sensors need to be cleaned (CAREFULLY or with a MAF cleaner aerosol can), and a good seafoam wouldn't hurt either. Air and fuel filters are a given. 180 degree thermostats might be nice for performance, but 195 and 215 degree thermostats will get you better fuel economy. If you have a bad wheel bearing or a dragging brake caliper, get it fixed.
C. Fuel/Engine Maintenance. Do not waste your money on mid grade or premium fuel unless you know for a fact it has a lower ethanol content. Higher octane fuel in a N/A low compression motor is a complete waste of money and may even reduce your fuel economy. The opposite is true if you have a boosted motor. Using lower onctane fuel can not only damage your engine, but will pull timing and consequently reduce efficiency. With regard to the Cruze, it has been noted that going up to midgrade or premium fuel will increase fuel economy. I can personally vouch for the truth of this claim and do recommend the use of midgrade or premium fuel in the Cruze.
If you use top tier fuel, it will have detergent additives that claim to allow your fuel to burn cleaner and leave fewer carbon deposits. This is more of a long-term fuel economy technique, as carbon build up will reduce the efficiency of your motor. While porting some cylinder heads on a V12 Jaguar motor, I snapped a photo of one of the valves so you could see what carbon buildup looks like. This had 160k miles on it.
It is highly recommended that you keep your fuel and intake system maintained with fuel system cleaners and intake cleaners such as seafoam that help clean the engine from carbon deposits so it doesn't get as bad as the above picture.
D. Weight. Chances are, you don't need all that junk in your trunk. Less weight means you use less energy to get moving. Your car is not your closet.
Once your car is running in its optimal conditions and you're getting "decent" fuel economy, we can move on to some behavioral techniques.
A. Turn off your heater. In the winter, if its not unbearably cold, suck it up and leave the heater off till the car warms up. The reason for this is that the car will run in open loop until it reaches ~160 degrees F. During this time, the engine's PCM will ignore some of its sensors (including the MAF) and run rich until it has warmed up enough for the sensors to all be functioning correctly. If you run the heater while the car is dumping fuel to try to warm up, you're just prolonging the time during which it stays in open loop mode and wasting additional fuel. This is because the heater core essentially acts like a radiator through which you're forcing cold air. It may not sound like it, but it does make a significant difference. You can turn the heater back on once you've reached ~180 degrees F.
B. Watch your RPMs. You'll burn more fuel if you accelerate more "spiritedly." Your shift points in an automatic will naturally be quite limited, but your throttle won't be. For manual transmissions, try to get into your highest gears as soon as possible. To use my Cruze as an example, I shift into 2nd gear as soon as possible, hit 2000RPM in 2nd, then keep RPMs below 1500 from 3rd through 6th gear. I'm in 5th gear at 35mph and 6th gear at 40mph, cruising at 1100RPM, quite literally sipping on fuel. Since I know this is easier said than done, here's a method you can use. Pretend there's slushy snow on the ground and accelerate accordingly. If a few people pass you, no big deal. The difference in a few car lengths will be mere seconds added to reaching your destination.
C. Watch your speed. 70mph might get you there 1-2 minutes faster, but you'll burn a lot more fuel. The ideal speed for fuel economy for most cars seems to be 55-65mph. Going from 65 to 75mph drops my fuel economy by 10mpg considering I'm pushing 55mpg at 65mph, and this is a car with several aerodynamic and drag-reducing features. Think of your car as a brick on wheels. It takes exponentially more fuel to cruise for each incremental increase in speed.
D. Turn cruise control off. Unless the road is completely flat. This applies mostly to in-town and back-road driving, as interstate highways/freeways will be limited to smaller and longer grades during which cruise control is fine to use. Your car will automatically adjust throttle to keep the car going about the same speed when it reaches a hill, which isn't ideal for fuel economy. Accelerate lightly before approaching a hill, allow the car to decelerate while climbing the hill, and accelerate lightly as you're going down the hill to get back up to speed. Of course, this only applies to smaller hills, but the concept is still there.
E. Conserve Energy. This one is a complete change in the way some of you drive in-town. Some of you will follow the car in front of you blindly or drive the same speed and slam on the brakes when the light had been red for a while. Every time you accelerate, you use fuel, which turns into energy. As your car is moving, it is carrying energy. That moving energy is lost (wasted) whenever you step on the brakes. So, how does one drive to keep from wasting energy? Let me give you an example scenario. I used google maps for this.
Above is one of the routes I take to get home every day. In the above picture, you'll see a left turn lane as well as a main lane, with peoples' brakes on, as the light is red. Imagine your speed is 45mph as this is a 45mph zone. What most people will do is follow the car in front of them regardless of what the traffic light is. What I do is let off the gas the moment I see a red light at that kind of distance. If the light stays red, I'll have coasted to 25-30mph before I have to hit the brakes. This increases the life of my brake pads and I'll have been in the same position as if I had followed closely and hit the brakes as hard as the person in front of me.
However, what happens 50% of the time is different. Usually, I'll see a red light at this distance, get off the throttle, and coast at a lower speed, and by the time I get closer to the intersection, the light will have turned green and the cars will have started moving. Here's the critical moment. By the time I reach the car directly in front of me, it will have accelerated to 15, maybe 20mph, and I will be able to continue moving at that speed instead of coming to a complete stop. That's 20mph of moving energy I did not lose by watching what was happening in front of me and driving accordingly. If I had followed the car in front of me more closely, I will have come to a complete stop and immediately have to accelerate again from a complete stop. This driving style requires you to fully understand that in 60 seconds, you will be in the exact same position whether you keep a constant speed until you have to brake and come to a complete stop, or cruise without using fuel and reach the intersection at a later time. The fact that it takes you longer to reach the intersection means that the cars are likely to have started moving by then, and you will have lost less moving energy in the process, and used less fuel. You will feel like you're moving slower, but you will notice that you will always be near the cars around you and thus will have lost no time.
Here are some questions you can ask yourself.
1. Could I have avoided coming to a complete stop?
2. Could I have predicted what would happen in front of me?
3. Was it necessary for me to keep a constant speed?
F. Have a Manual Transmission? Keep the transmission in gear while coasting to a stop. So long as you're above idle, the engine will actually shut off the fuel injectors and allow the transmission to turn the motor over, using zero fuel. While automatics will also do this, you have greater control with the manual. Don't put it in neutral when coming to a stop, leave it in gear until your RPM drops low enough to need to shift out of a gear.
G. Choose your route wisely. If you have several stops to make during a single drive and are not limited on time with regard to when you get there, drive to the farthest destination first, then work your way back. Otherwise, you may never allow the car to reach optimal operating temperature.
H. Don't idle. Your car doesn't actually need to warm up for minutes when you first start it up before you leave. This only applied to older vehicles that needed a substantial amount of time to allow oil to circulate and to fill the hydraulic lifters and is not an issue with newer cars. Get on the road soon after you start your car. If you're waiting for someone, turn your car off until they get there. Basically, unless you're moving or know you will be moving soon, turn the car off.
Here are things you should NOT do to increase fuel economy.
A. Drafting (closely following) a truck. People love doing it, but its not only unsafe, but also illegal. You're a pain in the ass of any truck driver because they can't see you, and you have zero time to react to debris that gets shot in your direction out from under truck tires. Trucks will kick up rocks and shoot them into your front fascia and windshield. Not only does it ruin your paint, but it can also crack your windshield. I've seen a truck kick up a broken hammer head that someone lost on the side of the road. Take a guess as to what happens if that comes flying toward your windshield at 70mph. I'll give you a hint; it doens't bounce off like a pebble. However, following an SUV or a Van at a safe distance is a good alternative.
B. Using higher octane fuel. Its useless and will not improve your fuel economy unless you're boosted or your car has a higher static compression from the factory (e.g. Northstar V8). This applies to the 1.8L, but not the 1.4L Turbo in the Cruze. The 1.4L Turbo motor benefits from higher octane fuel.
C. Driving significantly under the speed limit or accelerating like you were down a few cylinders. This makes you a road hazard. Drive the speed limit or 5 over (that's what they teach kids in my area) unless you expect to come to a complete stop or are approaching a small hill.