Chevrolet Cruze Forums banner

How to Get Better Fuel Economy

Tags
economy fuel
227K views 469 replies 100 participants last post by  snowwy66 
#1 · (Edited by Moderator)
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.



Mechanical


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.

E. Brakes. If your car pulls to one side or the other and you've checked the tire pressure and alignment make sure you don't have one or more brakes dragging.



Behavioral

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.
 
See less See more
2
#113 ·
I figured I'd update this here as well.

I filled up my tank after increasing tire pressure, driving the way I normally do. My highest FE went up from 41.3mpg to 44.7mpg. This is all in-town driving, but I give it a percentage of highway driving based on a 20mpg average for city and 60mph average for highway. Anything in between is a percentage of both.

I fill up at the same gas station every time, and let it fill up until I get to the first click and no further with 93 octane.

 
This post has been deleted
#114 · (Edited)
Sure is! I had the low fuel light on for the last 25 miles or so before I pulled into the gas station. Never trickled in more gas than the tank would hold on the first click. :)

Might also be worth noting that I had to use A/C for about 1-2 hours of that driving so I might have been able to squeeze in another 1-2mpg out of that.
 
This post has been deleted
#119 ·
What average speed?

The Cruze Eco manual is a heck-of-a-lot more fuel efficienct than is the Cruze automatic, such as the LTZ.

The manual cars typically exceed their EPA-Highway ratings, while the automatics struggle to even come close to matching them.
Keep in mind, EPA highway ratings are 58mph average with the engine already warm and a slight percentage adjustment. But yeah, manuals are the way to go. For FE. Even so, the automatics aren't anything to be scoffed at. The mileage isn't as high, but it's definitely pretty good.

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App
 
#121 ·
Keep in mind, EPA also factors in some room for variation. I think its something like 10% for city and 20% for highway. They rate their numbers less by that much so that what you actually get in the real world will be as good or better.

The only time this doesn't quite apply is with the Cruze Eco MT. Since they calculate their fuel economy on a dyno and determine fuel used by scanning what comes out of the tailpipe, they're probably not going to realize the benefits of the aero features that the Eco has.
 
#129 ·
I have incorporated most of extremerevolutoins techinques for increased fuel economy, and I must tell you that speed kills! I have been driving 65 in posted 75 zones, 55 in posted 65 zones, and at the speed limit under 55. Using coasting techniques, and driving much less agressively, I have been able to average 47.5 mpg for the last tank of gas (premium). Extremerevolution knows his stuff. If you want to ger maximum mpgs for your Eco, read his post.
 
#132 ·
I've only incorporated two tweaks/techniques: Maxed the tires and removed the resonator. The pump difference (not DIC) between my first and second fill-ups is a 9.9% improvement, from 28.86 to 31.72. I'm trying mightily to shift at the recommended points, but it just feels wrong. I grew up driving big-block Chevy and Dodge muscle cars with 3- and 4-speed transmissions so putting along in 6th at 40 mph is completely unnerving.
 
#133 ·
This may have already been said but its worth saying again if so. Up till recently my dealer had done all oil changes but I done it at home last month myself. I used M1 full synthetic oil and noticed about 2 more miles per gallon on my average, my driving habits and route have not changed at all so I can only contribute it to the full synthetic oil.
 
#135 ·
Im glad to hear this, I have 1,300 miles and plan to switch to AMSOIL fully synthetic oil at 5,000 miles. Best to date I have got is 38 mpg. Thats never over 60 mph and never over 2,000 rpms.

Sent from my DROID X2 using AutoGuide.Com Free App
 
#144 ·
Is that stock? My comfortable shift point for 6th is 45. Any lower and I lug the engine. My ECO MT is stock tuned.
 
#150 · (Edited)
If you floor the gas in 6th gear at 1300 RPM - really anywhere below 1900-2000 and you're asking it to go faster, all you're doing is bogging it down and making the engine detonate (yes, it will even on high octane gas if you strain it enough), pull timing, and strain. A modern engine will try to prevent detonation by adjusting the timing but you can still do damage.

By up-shifting at low rpm, you’re asking your motor to deliver power at its point of lowest “mechanical advantage”, which means you’re forcing the pistons, wrist pins, con-rods, crank, and journal bearings to accept the force of a large explosion pushing against a relatively unmovable object.

By all means, downshift for power if you need to go uphill or something and DON'T STRAIN THE ENGINE, just like an automatic transmission would do. Cruising around at low RPM and light throttle pressure is just fine - it will save you gas.
 
#151 · (Edited)
If you floor the gas in 6th gear at 1300 RPM - really anywhere below 1900-2000 and you're asking it to go faster, all you're doing is bogging it down and making the engine detonate (yes, it will even on high octane gas if you strain it enough), pull timing, and strain. A modern engine will try to prevent detonation by adjusting the timing but you can still do damage.

By all means, downshift for power if you need to go uphill or something like an automatic transmission would do. Cruising around at low RPM and light throttle pressure is just fine - it will save you gas.
Have any logs done on a Cruze that show this? Do you think it makes a difference at those RPMs if you're at 30% throttle or 100% throttle? I'm fairly certain even 30% throttle will allow enough air through to fill those cylinders to make any higher throttle levels entirely unnecessary.

If you floor it, one would suspect that you've switched over to power enrichment and are now running a much richer AFR, perhaps closer to 12.5.

Obviously, if you need to get moving, the natural choice is to downshift, but in all the time I spent tuning and datalogging the L67 in my Regal, I never registered a single count of knock at lower RPMs with higher loads. If I had a way to scan for knock, I'd do this myself, but I don't believe Torque scans for knock.

I understand that a lower RPM gives the fuel more time to ignite somewhere in the combustion chamber, but is this a real issue with the Cruze? Just trying to get an idea of whether or not this is actually an issue with our cars. I imagine it would depend heavily on the stock tune.
 
#152 · (Edited)
The stock tune definitely doesn't like moderate to hard acceleration below 1400 RPM. I tested this on the way home yesterday and again on the way to work this morning to rule out temperature differences. Light acceleration at any RPM abouve 1100 seems to be ok. Moderate to hard acceleration below 1400 and the car shivers (like we do when cold). By downshifting I can get the car to stop shivering and also accelerate. I understand your comment that the instant mpg readout isn't very accurate during hard acceleration, but I have also noticed that it runs about the same or a little lower when the engine is lugging vs. downshifting to accelerate. The instant mpg reading certainly stays lower for a lot longer if I don't downshift.

This tank is Shell 89 octane, but I noticed the lug on Shell 91 as well and I had the A/C off for this testing.
 
#153 ·
I know exactly what you mean by the car shivering. I believe the cause of that vibration is the fact that this is a 4-cylinder, which generally won't be as smooth as a V6 or a V8. At those RPMs, the engine produces significantly more vibration. GM did a great job of damping that vibration with a very well thought out 4-point engine mounting system, but at those lower RPMs, you're putting stress on those mounts and some vibration is being transferred from the engine into the car. If you accelerate slowly, you'll notice the frequency of those vibrations increases with engine RPM.

Like I said, the instant readout cannot be used during acceleration, no matter what value it shows. It is not accurate at all. That said, if I need to climb a hill and I notice that I can't accelerate in a certain gear, I'll downshift because it's pointless to try otherwise, but I can usually get over small hills at 40mph in 6th without a problem. I've never actually floored the gas in 5th or 6th gear. If I need to accelerate rapidly, a lower gear is the logical choice, lol.

I also use 93 octane Shell. I fill up at the same gas station, from the same exact pump (I'll even wait for someone to finish pumping just so I can use that specific pump), at about the same time of the day give or take 30 minutes. Every time I've tried to keep my RPMs above 1500 while accelerating, my total average has been lower.
 
#156 ·
Oh, I know I want to, but I have just under $19k worth of car loan debt that I should spend that money on instead, lol. Maybe after the 5 years is up and HPTuners has something available, I'll just tune it myself, but for now, I can't bring myself to do it.

That, and I see no benefit for it. The car is plenty quick to get me around where I need to go, and I don't feel like spending hundreds if not thousands of dollars to try to get into the mid 15s when I can get my speed fix in my 95 Regal, which will run mid 13s all day long.
 
#158 · (Edited)
I go over a bridge(I'd say 25-30 degree hill) each way to work and if I can hit it at 70, I can keep the throttle lightly depressed with the DIC reading around 40 mpg and decelerate to the top of it(ending around 55 mph). Otherwise I have to downshift to 5th. And even in 5th I slow down if I'm at around 60 when I hit it. This car definitely has a hard time maintaining speed in higher gears when faced with steep grades.
 
#161 ·
Nice thread at CleanMPG forums. Wayne had a pre-release model on top of it.

I tried shifting at the RPMs you shift at. That's a no-go at altitude with one exception - stop & go traffic. Turns out the Cruze ECO MT is really good at pulse & coast. I didn't top 1800 RPM the entire time and most of my shifts were at 1500, even 1-2. When I did take it up to 1800 I didn't shift; I simply coasted until I caught up with the next bottleneck in the road taking advantage of DFCO and avoided my brakes for a large part of the commute.
 
#168 ·
Thanks for the write up. I'll practice some of these. I've been practicing these techniques with my bike.

One technique I notice you didn't mention was Pulse and Glide. Read it and you'll get even better milage.

Driving technique: exploring 'Pulse and Glide' - MetroMPG.com
I didn't mention it because it isn't practical and is beyond the scope of this thread. As mentioned previously, the scope of this thread is to provide simple, effective, practical, and cheap ways to improve fuel economy. Basically, things that everyone can do easily and still get appreciable gains in fuel economy. The article even says quite clearly that it's not something that's practical. Those of us with manual transmissions would need to take 6 discreet steps every 16 seconds of driving. I'd be more concerned with how much that's wearing out my clutch and throwout bearings than the 5-10% fuel economy I'd be gaining.
 
#172 ·
One thing I noticed today while scanning with Torque is something I had suspected. The car tends to drive itself with regard to throttle position. I'll verify this with a few more scans, but I tested this earlier today while going 45mph in 6th gear. I floored the gas and watched the recorded throttle position in Torque and it didn't go past 51%. If I downshifted and allows RPMs to rise, I would indeed be able to hit higher throttle positions. I wonder if the PCM ignores the fact that you're flooring the gas at very low RPMs in a high gear. Perhaps the engineers thought that if you needed to floor the gas, you should be in a lower gear anyway.

I'll scan on my way to work tomorrow and report back.
 
#173 ·
One thing I noticed today while scanning with Torque is something I had suspected. The car tends to drive itself with regard to throttle position. I'll verify this with a few more scans, but I tested this earlier today while going 45mph in 6th gear. I floored the gas and watched the recorded throttle position in Torque and it didn't go past 51%. If I downshifted and allows RPMs to rise, I would indeed be able to hit higher throttle positions. I wonder if the PCM ignores the fact that you're flooring the gas at very low RPMs in a high gear. Perhaps the engineers thought that if you needed to floor the gas, you should be in a lower gear anyway.
Think about what happens in a carbeurated engine (no computer control). If you floor the accelerator pedal at low RPM you feed more fuel in than can be properly burned and can actually flood the engine while moving. Having the ECU control the injectors to prevent this makes a lot of sense.
 
#174 ·
I'm not a technician, but I always suspected this too, I alway noted that if you accelerate too much ( in relationship with rpm and speed) the car wouldn't go quick as you want, for this I always use accelerator gradually and, in more than 2 years, I reached the bottom end only one or twice.

were do you bought the transmitter for use torque? is the one on aliexpress from china with bluetooth? on a noika 5800 I'll use alway torque or I have to use another program?

thankyou
 
#176 ·
I can definitely report that high speed mountain driving over I-70 doesn't have that much of an impact on fuel economy. Drove from Denver to Rifle Falls State Park and back today. This drive goes over two passes (actually through a tunnel under one at 10,000 ft) and my pump to pump MPG for the out and back was 47.3 MPG. The DIC read 49.8 MPG. My actual MPG was somewhere in-between, but since first click-off was almost a gallon less than I put in the tank when I got back, I suspect it was closer to 49 MPG. Total distance was over 400 miles and average speed was over 50 MPH. I went over Vail Pass and through the Eisenhower/Johnson tunnels twice. Vail pass is at 10,500 ft and is the highest point on the US Interstate system. The Eisenhower/Johnson tunnels are just under 10,000 ft. Speed limits on this stretch of I-70 range from 65 to 75 except for the Glenwood Canyon section, which is 50 but everyone was doing 55. Other than Glenwood Canyon traffic was moving 2-3 over the posted speed limit. I set my Cruze control at the posted speed limit or 55, whichever was higher.

A couple of observations about the Cruze's 1.4T engine.

First, the non-ECO MT should be able to do this without ever downshifting to 5th gear. I make this claim based on the fact the ECO MT 5th gear is almost identical to the non-ECO MT's 6th gear and that I didn't need to downshift below 5th gear except when slowing down for traffic on the way back. Most of the time I was in 6th gear, even going uphill. There are a few steep hills (west immediately out of Denver, Georgetown hill westbound, the top of the Eisenhower tunnel approaches, and Vail Pass in both directions) that required 5th gear. The car was at 2300 RPM while in 5th.

Second, the ECO MT doesn't engine brake, even at 4500 RPM in 3rd gear. I still had to use the brakes to keep the speed down. I wasn't worried about the car's ability to handle the curves but simply didn't want to be flying down the side of a mountain so fast that the local and state troopers would want to give me a second look.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top