Aftermarket Parts That increase mpg?

[Sonic883r]

Has anyone put on some aftermarket parts and noticed a slight mpg gain out of it? Right now I'm getting 38mpg. I'm supposed to be getting a k&n air filter in the mail today to test it out.

 

[sx sonic]

Most members have claimed a 2-4 MPG improvement with a tune.(usually Trifecta)

Some have also claimed benefits by changing the air filter and many more claim better mpg by using premium fuel. usually stating a 1-2mpg improvement.... but ive seen as much as 5mpg claimed by switching to 93 oct :rolls eyes:

But the biggest mpg improver is you. Slowing down 5-10mph, coasting to stops, easy acceleration, limiting idle time, and short shifting can be worth 5 or more mpg.

There's a few of us that have gotten at or above 50mpg with a "driver mod"

 

[Swordsmith]

I see far too much swing in my mpg from uncontrolled factors to be able to identify the 1-2mph sorts of gains most aftermarket parts promise.

For a controlled test you need to drive a long distance on the same road in the same weather with your car having the same load, using cruise control and resuming speed so the setting isn't at all different. Also use same pump for each fillup, that sort of thing.

When it's a 5 mpg difference it's a lot easier to prove, but even so... I can get 22mpg from one tank and 31mpg from another tank of the same fuel, same pump, just by changing how I drive... with that much swing, it's pretty hard to be sure one way or the other about the little gains.

 

[Sonic883r]

I have been looking into the trifecta mod for some time but I'm going to wait until I get a cold air intake and exhaust. This morning I decided to drive like an old lady haha I usually get around 27 28 because I have a heavy foot but was surprised that I got 38

 

[barch88]

You may save a tiny, TINY bit of MPG (1-2 at the MOST, but like it was said before how do you know it was the fuel?) by using premium fuel, but to be honest it'll be more of a savings by not paying for premium and just using regular. Unless you car requires 93 octane or higher (which ours don't - stock..) it's pointless to use it.

 

[Swordsmith]

You may save a tiny, TINY bit of MPG (1-2 at the MOST, but like it was said before how do you know it was the fuel?) by using premium fuel, but to be honest it'll be more of a savings by not paying for premium and just using regular. Unless you car requires 93 octane or higher (which ours don't - stock..) it's pointless to use it.

This may or may not be true. It is true for some cars and not for others.

The Sonic 1.4T, in particular, has a clever system using the knock sensor, it starts up as if it had high octane fuel, and on first detection of knock dials down the timing a little, repeat until knock goes away. This means it automatically runs at the highest possible timing for the specific octane you are running. That's Stock tuned, right out of the factory, it already gives you more power on 93, less on 91, less still on 87.

That said, though, you may still be correct in your thinking that the difference in price more than makes up for any marginal increase in mpg (if there is any at all... the little testing I've seen has all been regarding maximum power, not optimal mpg). Or you may not. Without rigorous testing, it's hard to tell really. Say the price difference is a typical one I saw a lot last winter, $3.55 a gallon for 87, $3.85 for 93. That's an 8% increase in price. So if you go from 37mpg on 87 to 40mpg on 93, you are paying exactly the same amount per mile both ways. An increase of More than 3mpg would actually mean it is cheaper per mile to get the higher octane.

Price difference as a percentage varies though, and as you say it is really hard to figure out what if any mpg cost there is to switching down from 93 (which the engine runs best with) to 87 (which the clever engineers at GM have allowed it to run acceptably with).

Tune your car, alter intake, exhaust, this or that, and your equation is going to vary wildly from that of a stock car, so you need to find those answers for yourself on a case by case basis. But the tests have to be careful and rigorous to avoid screwing up the data; you can get much more than 8% difference in mpg just by changing your driving behavior... including just making use of the additional power 93 gives you to accelerate like a rocket!

 

[cndctrdj]

Driver mod is the best for mpg. And coasting to a stop is worse for gas mileage than downshifting and having the engine slow you down.

Also any bolt on mod is going to give you better mpg. Exhaust, intake stuff like that because they make the engine more efficient

 

[Maddmatts]

If you're going for performance upgrades solely to increase economy, I'd say save your money. It will take years to get back what you spent let alone start saving you money.

For those paying for performance, the added economy is just icing.

When it comes time to replace the tires you can opt for thinner ones to help reduce rolling resistance.

 

[barch88]

This may or may not be true. It is true for some cars and not for others.

The Sonic 1.4T, in particular, has a clever system using the knock sensor, it starts up as if it had high octane fuel, and on first detection of knock dials down the timing a little, repeat until knock goes away. This means it automatically runs at the highest possible timing for the specific octane you are running. That's Stock tuned, right out of the factory, it already gives you more power on 93, less on 91, less still on 87.

That said, though, you may still be correct in your thinking that the difference in price more than makes up for any marginal increase in mpg (if there is any at all... the little testing I've seen has all been regarding maximum power, not optimal mpg). Or you may not. Without rigorous testing, it's hard to tell really. Say the price difference is a typical one I saw a lot last winter, $3.55 a gallon for 87, $3.85 for 93. That's an 8% increase in price. So if you go from 37mpg on 87 to 40mpg on 93, you are paying exactly the same amount per mile both ways. An increase of More than 3mpg would actually mean it is cheaper per mile to get the higher octane.

Price difference as a percentage varies though, and as you say it is really hard to figure out what if any mpg cost there is to switching down from 93 (which the engine runs best with) to 87 (which the clever engineers at GM have allowed it to run acceptably with).

Tune your car, alter intake, exhaust, this or that, and your equation is going to vary wildly from that of a stock car, so you need to find those answers for yourself on a case by case basis. But the tests have to be careful and rigorous to avoid screwing up the data; you can get much more than 8% difference in mpg just by changing your driving behavior... including just making use of the additional power 93 gives you to accelerate like a rocket!

Yeah, well put.

Also, stickers increase hp.

 

[Swordsmith]

If you're going for performance upgrades solely to increase economy, I'd say save your money. It will take years to get back what you spent let alone start saving you money.

For those paying for performance, the added economy is just icing.

You have a point there, if the sole reason to increase mpg is to save money, there aren't many mods that will pay for themselves.

Consider though the performance angle... there aren't any performance mods that pay for themselves either; the stock sonic, even the lowly 1.8 stock sonic, is more car than you need, with better performance than anything else in the segment under 20K, at least anything I test drove and I drove a LOT of those little hatches.

Some folks pursue mpg the way some of use pursue performance; as a goal in and of itself, not to save money.

What has been reported as improving mpg? I can think of several, although I haven't seen good data back on any of them to prove it one way or the other.

Intakes. Every intake from just replacing your filter with a K&N, to SAB mods, to full blown ZZP or DDM has been reported by someone to have increased their mpg. The one most likely to do this would be the reviled (by power modders) Injen, which is basically a WAI, which should in theory result in increased mpg. It would be possible to build an intake that warms the air even more, just as some folks are doing cold air thru the fog vents for more power.

Exhaust. Honestly exhaust is mostly about noise, and to some extent about power, but I have heard mpg claims made here too.

Tune. Lots of folks have said they see an increase in mpg using a trifecta tune. Interestingly, many report more gain on the performance tune than the "eco" one... and yet a recent post by Jerry at BNR says that the "eco" tune for the sonic is really just the stock tune.

Tires. Hardly anyone likes the Hankooks the car comes with. It should be easy to find something lighter with lower rolling resistance and see some improvement.

Wheels. Here too, lighter wheels better. Mostly we get these for looks, but you could find some aero designs that might help... I saw a report of some gains from a guy that built wheel covers using pizza pans.

Reducing weight. Go on a diet (the infamous driver mod), but also start taking weight out of the car. Consider getting rid of your spare, replacing it with a can of fix-a-flat, a cell phone, and a AAA card. Go hardcore and replace major body parts with carbon fiber. Lots of other places weight can be lost. Move less mass, use less fuel.

My personal favorite; convert to E85. Yeah, your miles per gallon of fuel go down, but your miles per gallon of gasoline go way way up, since there's very little gasoline in a gallon of E85.

But seriously, no matter what you do, altering driving behavior is still going to be far and away the biggest change you can make, it's free, and doesn't violate your warranty. Consider Smit and me; same basic car with more or less the same mods, he can get 60 miles from a gallon and I can get 22 miles from a gallon. I don't care what you do to the car it isn't going to make a 300% difference.

 

[Sonic883r]

I haven't even put any premium in my tank yet im just filling up with chevron regular I just put a k&n filter and did my break-in oil change last light my mpg is now 41mpg from 38mpg it wanted to keep going but then I started to get into the city limits and it went down to 36 :blankface:

 

[Preloader]

Not quite "aftermarket", more like "pre-market" belly pan. 40psi in your tires. Full Synth motor oil.

 

[sx sonic]

Driver mod is the best for mpg. And coasting to a stop is worse for gas mileage than downshifting and having the engine slow you down.

Also any bolt on mod is going to give you better mpg. Exhaust, intake stuff like that because they make the engine more efficient

Down shifting is only more fuel efficient if the car goes into DCFC, which it doesnt always do just because you're in gear and off the throttle.

Conversely if it doesn't go into DCFC you are getting worse instantaneous MPG by leaving it in gear AND you're slowing down faster which depending on circumstances could mean you're far from maximizing economy.


Put simply coasting to a stop IS more fuel efficient than late braking to a stop

Down shifting to a stop CAN be more fuel effecient than coasting. From my testing in the sonic downshifting is USUALLY yields worse than coasting.

 

[$ub$onic]

I would think downshifting would yield better due to the fact of the injector cutout

 

[Swordsmith]

I would think downshifting would yield better due to the fact of the injector cutout

SX Sonics point is that injector cutout isn't a fact, it's something that happens only under the right conditions. If it doesn't happen, then you don't get the "zero gallons per second" effect that is the reason this can be better than nuetral coasting.

Meanwhile, with either technique, the point isn't so much about how you glide to a stop, as it is that you don't keep spending gas to keep speed up and then brake all that energy away. Get off the gas pedal early, there's no hurry to get to the stop light... and even better you might not have to stop at all, accelerating back up to 50 from 25 is a lot less costly than accelerating from zero.

More gas saving ideas, getting more esoteric now: blocking off some of your front grill (either with something removeable, or with something that opens and closes). Changing the spoiler to more of a kammback shape or even add a full fledged "boat tail" like this guy is doing to his Insight:

Also note how the rear wheelwell of the Insight has covers to reduce drag, since the wheels don't have to turn they don't hit this wall the way front wheels would. You could add those to the Sonic. (they are standard on that Insight)

 

[barch88]

Not quite "aftermarket", more like "pre-market" belly pan. 40psi in your tires. Full Synth motor oil.

Stock tires call for 37 PSI - at least my 15 or 16's do (whatever comes on LT). Should I put 40 in them? I notice they look kinda dull even when they are technically "full"

 

[Swordsmith]

Tire pressure is about tradeoffs. The higher the pressure, the less contact area they have with the ground and the lower their rolling resistance. This means higher pressure = higher mpg BUT lower pressure = greater power and skid resistance.

Those are both when within the normal range of a tire, mind you, at very low pressure your tire will be total crap at everything. At very high pressure, it will explode. But in between extremes, they are a reasonable approximation.

I find 40 PSI to be reasonably good for control and acceleration while lowering resistance pretty well. In the winter or rainy season, or when going to the track, I might drop that down to 35 or even 30; sometimes I'd rather have contact with the ground than save a few pennies. There are folks out there running as high as 42 PSI.

This also helps more at high speeds than at low speeds, if you're doing a lot of city driving tire pressure hardly matters at all, if you're out on the freeway going long distances it probably matters a lot more. I wouldn't go real high if your drive takes you through curvy mountain roads or lots of rain or snow, though, just not worth it.

Nice thing is this "mod" is temporary and free (if you have a compressor) or just costs 50 cents or so (if you are using a coin operated air pump). so you can adjust until you're happy, and adjust again to fit conditions if you want to get really fiddly about it.

 

[mitdr774]

With everything I have done to my car I managed to increase my highway MPG by a whole 1.3 MPG compared to stock (based on a trip I take every year, averaged for the whole trip). That being said, while I have a goal of hitting 50 MPG I am also making changes that improve overall performance. My goal to hit 50 MPG is not based on recouping money spent on parts. I know that will never happen. This year I came close to hitting an average of 45 MPG for the trip, but I fell 0.52 MPG short.

 

[Swordsmith]

The boat tail mod is so over the top, but it is A) remove-able, B) creates additional storage space and C) reports to gain 9.7% mpg, and finally D) is made of wood and cardboard and waterproofing, so really we're just talking time. Assuming you DIY and enjoy this sort of thing, it seems almost like a good idea; something you can keep in the garage and only put on when you're off on a long trip, store some lightweight luggage inside and have fun!

I may not be sufficiently committed to the high mpg goal to do it, but I hope some crazy Sonic owners do, I want to see it on both HB and Sedan.

 

[sx sonic]

Swordsmith I'd advise against going below 30 psi on the tires for daily driving.

From my observations as a tech most tires start to flex progressively more and more below ~30-32psi. This makes the car wallow more, starts having a big negative impact on mpg, really starts to wear out the outside edges of the tire (it was easy to tell owners that didn't maintain tire psi by treadwear alone), and the extra sidewall flex causes the tire to heat up more. On real low tires the flex and heat destroys the tire and causes a blowout.

I consider 34-38 to be a good range for standard load tires (usually 44psi max). Sidewall deflection changes marginally around this pressure range which is good thing...... And great for people that don't check their tire pressure because it usually won't drop to a less than ideal pressure when temps drop.

38 to max pressure (typically is 44 psi, check sidewall) is marginally better for mpg and tire wear. As I mentioned above around 30 psi the sidewall and contact patch become more stable (you can visibly see the difference between 28 and 30psi. But 34 and 40psi appear almost identical), and additional pressure has a smaller and smaller impact on sidewall flex, mpg, and tire wear.