mods that will improve fuel economy?

[Dackelone]

19 MPG is not bad. The 135i can get much worse. Like 6 mph at WOT on the Autobahns. I usually average around 22 mpg. IF you use the cruise control and do not go faster than 65 mph you can get 28 mph. I have.

You best bet (besides making sure your air filter is clean and your tire pressures are ok) is to hyper cruise. Coast as much as possible. Don't step onto teh gas pedal hard. Try to press it ever so lightly.

Put the board computer into instanteous MPG and use that as a gauge as to how hard to accelerate/drive. It doesn't take that much difference is pressing the pedal down to go from low MPG to decent MPG. It is all how hard you press down on the loud pedal and how high you rev(speed, mph) that engine.

[Vigilante375]

Oh, I see now....I shouldn't use my Zune nor radio since I wont get that extra .00005 mpg that I need, because that puts soooooo much strain on the engine. And I guess drafting a semi is a good idea, you get a 1MPG increase in fuel economy. Thats cool, I guess I'll always slipstream a semi and then pay for a new windshield because I get great mileage!

[cooler2442]

I actually get better MPG with my catless downpipe and JB4 BUT that is only if you never ever punch it or anything of that sort. If you do then you get worse MPG. But if I leave it in D all day and never shift myself or gas it hard then I get better MPG.

[splashz]

Originally Posted by ptack

You bought a relatively expensive 300 hp convertible and now you want to save a couple of bucks on gas? Did you think it was a Prius?

I hate comments like this. Yes, I bought an expensive car. You know why I can buy an expensive car? Because I'm smart with my money. I save money where I can. Just because I have this car, I shouldn't care about money anymore?? It's a stupid comment. Saving money now means I can buy even more expensive things in the future.

[ptack]

No, it's a stupid rationalization to say you're smart with your money so you bought a 300 hp convertible. You made an emotional choice to buy a very unpractical vehicle which you are trying to make economical.

[RPM90]

Originally Posted by splashz

I just bought a used 135i convertible and I'm loving it so far. However I'm not getting great gas mileage. About 21mpg and I drive mostly highway (much of the time in traffic though). I'm considering bringing it in to a shop just to make sure everything is working efficiently.

Performance upgrades are nice but honestly, I'm pretty happy with the power of my car since I'm coming from a much less powerful car. I'd rather do something that will make my car more efficient and help with the gas mileage. Anything like that? I'm pretty new to modding cars but my buddy is into it and is willing to help me.

I have a MT 135i and drive mixed highway/non.
My average MPG is between 21-22.
Your vert is a good deal heavier, so 21mpg ain't bad if you're hitting the loud pedal on occasion.

You could increase your tire pressure by about 3psi front and rear since you do mostly highway driving. But, that will net only so much.
It's not like you'll see 24-25mpg average, mixed driving, from where you are now.

I've seen 25-28mpg on the computer on long, flat, and straight highway, going steady 80mph. But, play a bit with that and hit 90mph with hard accel to pass and mpg quickly drops back to 21-22mpg.
Throttle input/control and wind drag/speed has the biggest effect on MPG on the highway.

[1speedbike]

I drive 50 miles per day, roughly. I get 22 mpg. I don't drive like a doofus. I punch it when I can (aka close to WOT every highway onramp and red light.. hey with the traffic around here I gotta have fun somehow), and then settle into a nice cruising speed of about 75-80 mph on the highway.

If I drove like a lot of people that I commonly see on the road, I can easily get 5 mpg less (17 mpg). If I drove like a prius driver SHOULD drive (nevermind that I see them going 80+ mph in the left lane pretty often.. definitely doing the whole hybrid thing wrong) I could probably get more along the lines of 26 mpg as Dackel mentioned.

But lets say I drive those 50 miles for 5 days a week for 48 weeks a year. In reality I drive a lot more, especially on weekends. Let's say gas prices stay at around $3.50 for 93. They're more than that right now and will likely stay more than that for a while.

By NOT driving like a dick and getting 17 mpg I can save close to 600 dollars a year. By driving like a saint and getting 26 mpg, I can get another 500 dollars. Conservative estimates here too.

Does this make a HUGE impact in anyone's total money stockpile? Probably not. But if anyone thinks 600 free bucks for NOT driving like a dick is something to put down (not even hypermiling and everything.. just driving like I normally do), then you either have a lot of money to waste, or you're just very unconcerned with money. If Allstate offered the "not a dick driver" discount and you got 500 bucks a year discount for not driving like a dick, I reckon a lot of people would jump on the offer. Don't see this as any different. How you drive plays a pretty big role in your fuel economy, especially on this car which has the potential for both frugality and abysmal economy.

Also, most people are aware of this, but some are surprisingly not. 55 is the ideal speed for fuel economy. Any higher, and the mileage drops too quickly in relation to your speed. Any lower, and yes you're getting better economy, but you're also going slower and taking more time to get to your destination, thus spending more time burning fuel. 55-60 is the sweet spot that balances speed and consumption.

[Groundzero]

After driving 10 hours yesterday to Vermont and back I ended up averaging 27.6mpg according to the computer. I had 22 average between the drive there and spirited back-road driving, then drafted a 18 wheeler most of the way home which bumped up the average a lot.

Like others said, I think changing driving habits will save the most gas and therefore money. Spending money on mods to save money on gas doesn't make sense to me.

[Ash83]

Originally Posted by igzekyativ

remove the turbos..

[fourtailpipes]

Originally Posted by Vigilante375

Oh, I see now....I shouldn't use my Zune nor radio since I wont get that extra .00005 mpg that I need, because that puts soooooo much strain on the engine. And I guess drafting a semi is a good idea, you get a 1MPG increase in fuel economy. Thats cool, I guess I'll always slipstream a semi and then pay for a new windshield because I get great mileage!

there wasn't a more dramatic eye-roll emoticon, so i had to settle for that^ one.

[doublevanosrc]

Originally Posted by igzekyativ

remove the turbos..

[fourtailpipes]

Originally Posted by 1speedbike

Also, most people are aware of this, but some are surprisingly not. 55 is the ideal speed for fuel economy. Any higher, and the mileage drops too quickly in relation to your speed. Any lower, and yes you're getting better economy, but you're also going slower and taking more time to get to your destination, thus spending more time burning fuel. 55-60 is the sweet spot that balances speed and consumption.

it's funny you bring this up... my old college roomate is doing his thesis for a PhD in materials science engineering about exactly this. so far, his research has shown that in more modern engines, the rpm and speed ranges for optimal fuel economy tend to be quite a bit higher, mostly due to recent improvements in thermal efficiency (and aerodynamics). his data isn't all compiled yet, but he's telling me that most of his data points toward nearly 70mph being the best for his targeted data set (cars manufactured after 1/1/2000). obviously this is a data set with MANY extraneous points, so at best you can conclude on a sweet spot, not a rule.

[1speedbike]

Originally Posted by fourtailpipes

it's funny you bring this up... my old college roomate is doing his thesis for a PhD in materials science engineering about exactly this. so far, his research has shown that in more modern engines, the rpm and speed ranges for optimal fuel economy tend to be quite a bit higher, mostly due to recent improvements in thermal efficiency (and aerodynamics). his data isn't all compiled yet, but he's telling me that most of his data points toward nearly 70mph being the best for his targeted data set (cars manufactured after 1/1/2000). obviously this is a data set with MANY extraneous points, so at best you can conclude on a sweet spot, not a rule.

That's good to know! I know vehicle aerodynamics affected this "sweet spot" but didn't realize thermal efficiency also played a role. I assume that the "55" rule was made back during the 70's oil crisis when cars weren't exactly the pinnacle of aerodynamic design. I guess we'll have to play around with our speeds and see at what speed and higher the steepest "drop-off" for efficiency is

[fourtailpipes]

Originally Posted by 1speedbike

That's good to know! I know vehicle aerodynamics affected this "sweet spot" but didn't realize thermal efficiency also played a role. I assume that the "55" rule was made back during the 70's oil crisis when cars weren't exactly the pinnacle of aerodynamic design. I guess we'll have to play around with our speeds and see at what speed and higher the steepest "drop-off" for efficiency is

you're spot on about the 55 rule. the conclusion he's pointing toward is that speed limits are economically prohibitive, and need to be readjusted for current technology. as far as i know, even the most efficient internal combustion automobile engines still don't reach even 30% thermal efficiency! there are ceramic-block engines in development which reach significantly higher levels of thermal efficiency at much higher RPMs, but are totally inappropriate for commuter vehicles.

this is an aside, but i'd argue that most 2000+ cars are safer at 70 than most 1975 cars were at 55, so the safety concern, which is obviously the biggest counter-argument, is really nothing more than politics and perceptions. like clarkson said... speed doesn't kill; it's suddenly becoming stationary that's dangerous! so you should also speed

[Experimental]

Originally Posted by cooler2442

I actually get better MPG with my catless downpipe and JB4 BUT that is only if you never ever punch it or anything of that sort. If you do then you get worse MPG. But if I leave it in D all day and never shift myself or gas it hard then I get better MPG.

Good info.

Any estimate on what kind of improvement you see with the downpipes?

[cooler2442]

Originally Posted by Experimental

Good info.

Any estimate on what kind of improvement you see with the downpipes?

I haven't done super accurate recordings but during long trips such as 1hour+ on the freeway I have seen a consistent 33-34mpg highway. But that is with my N55 JB4 Stage 2 Beta, Downpipes and keeping it in cruise control during that time. Never saw that high highway numbers when I was stock.

Can't comment on city because I can never keep myself from aggressively driving since it is just to tempting with my mods. Most likely I get worse city just because I drive more aggressively to hear my burbling on downshifts and exhaust.

[ken1137]

Yep, 21 mpg isn't bad...I'm still laughing at the fact someone has a Zune

[DAC17]

Originally Posted by Allencic

For a 135 I suspect your mileage is pretty typical.

In a long lifetime of driving I've had a number of good friends who complained about how lousy their mileage was. Without exception they all had several driving traits in common. First, they used the accelerator and brake pedals as on/off switches. Either full on or full off. Frankly, to ride with them was really unpleasant and often simply unsafe. Second, they never looked far ahead at the traffic so they could make smooth transitions in speed. An obvious red light ahead was usually met with a sudden, surprised need to stop quickly instead of smoothly. Third, their lack of situational awareness of the traffic around them often found them jammed in packs of cars going either too slow or fast, on and off the brakes and gas. Simply unpleasant, uneconomical driving style. Their jerky driving style often resulted in moving violation tickets. In short, they were crappy drivers.

+1.

[yaymitch]

A 128i convertible might have been a smarter choice if gas mileage is a concern. It is less expensive and gets better mileage. But if you want more performance it comes at the expense of gas mileage. I just traded a 500Hp, 480tq, 6.2L V8 monster for this car. I get marginally better gas mileage with the 135i. Maybe 3-4 MPG better is all.

[ryancappuccino]

Originally Posted by splashz

I hate comments like this. Yes, I bought an expensive car. You know why I can buy an expensive car? Because I'm smart with my money. I save money where I can. Just because I have this car, I shouldn't care about money anymore?? It's a stupid comment. Saving money now means I can buy even more expensive things in the future.

Agreed. I do a lot of city driving and I have a heavy foot. I had a really slow car before.... I also have the convertible and I am averaging under 17 a tank but I'm in stop and go downtown Boston traffic for 2+ hours a day.

[ryancappuccino]

Originally Posted by ken1137

Yep, 21 mpg isn't bad...I'm still laughing at the fact someone has a Zune

Zune! ...I had one too back in the day....

[ryancappuccino]

Originally Posted by cooler2442

Can't comment on city because I can never keep myself from aggressively driving since it is just to tempting with my mods. Most likely I get worse city just because I drive more aggressively to hear my burbling on downshifts and exhaust.

Hahaha I agree and Im in the city most of the time. I just love whipping it hard at 6MPG and listen to it put in work.