How to get the best MPG with the 1.4T 6MT

[m3t4lm4n222]

So, I now officially have 3000 miles racked on my 1.4T Sonic with the 6 speed manual and I am only averaging (Keep in mind, this is during the winter season using winter blend gases) about 31MPG. I probably drive 50/50 City/Highway, maybe 60/40.

My driving style is basically...keep the RPM's as low as possible. I do skip shift. I'll often go from 30MPH up to 50MPH in 4th, then skip to 6th, sometime i'll go from 20MPH to 35-40MPH in 3rd and skip to 5th, etc.

Well, my gearhead brother came into town for a couple weeks and I let him drive while I was in the car and he drove much more aggressively. He'd keep the RPM's higher, often cruising @ 2K-3K RPM depending upon speed, gear, etc and even drove the car up to about 5K RPM's. The odd thing is that I noticed my MPG counter actually noted that I was getting better fuel economy while he was driving more aggressively, keeping the RPM's high and accelerating faster.

I have always been under the impression that keeping the RPM's as low as possible means less fuel being consumed, less stress on the engine, longer engine life.

Any thoughts?

 

[Swordsmith]

Driving style certainly matters a lot, but my experience is the opposite of what you are reporting; I normally drive somewhat aggressively, and when I deliberately ease off and drive gently, I get much better mpg. I tested this one day, got a full load of friends and drove around the Dallas area in a mix of highway and city miles using most of a tank, driving normally, then repeated the route using gentle acceleration and keeping the speed at or under the limit; I used a third less gas on the second lap.

I was not watching my rpms at that time, nor have I really made a practice of doing so. Based on your report here, I would guess that the relationship between rpms and mpg is more complex than a simple "keep it low" plan; perhaps accelerating at too low an rpm level is as bad as cruising at too high of one. If your early shifting and skip shifting is putting too much of a load on the engine, perhaps your brother got better mpg simply by shifting at proper intervals and not lugging.

When I skip shift, it is because I am ready to cruise; I accelerate through first second third, at which point I am going highway speed and go directly to sixth, no longer accelerating. Meanwhile when I am driving more gently, I do the same thing, but shift earlier, and also pick up fourth on the way up... although rarely fifth, which strikes me as a useless gear.

Driving gently I also keep out of boost; when I am pushing it (which I normally do) the pedal goes down and the boost climbs. Gently, the boost gauge never goes postive.

I'd like to see you try some experiments to see if you can duplicate your brother's results, on the surface they do seem very interesting.

 

[Papasonic]

A lot of lesser experienced manual transmission owners tend to want to shift into too high a gear ratio too early, thinking that would improve economy. The trick is to keep the engine RPM low, but also not to lug the engine to the point that it won't readily accelerate. If the gear ratio is too high for the vehicle to readily accelerate with moderate throttle input; the engine will consume copious amounts of excess fuel. Cold winter driving conditions, hilly terrain, bucking wind, and excess speed all contribute to excessive fuel consumption.

 

[CheapFuneral]

A lot of lesser experienced manual transmission owners tend to want to shift into too high a gear ratio too early, thinking that would improve economy. The trick is to keep the engine RPM low, but also not to lug the engine to the point that it won't readily accelerate. If the gear ratio is too high for the vehicle to readily accelerate with moderate throttle input; the engine will consume copious amounts of excess fuel. Cold winter driving conditions, hilly terrain, bucking wind, and excess speed all contribute to excessive fuel consumption.

This is correct, you don't want high rpms but you also don't want the engine to try harder to do its job. If your rpms are to low you actually have to use more gas at less rpm to keep the engine going. Also when highway driving I like to accelerate fast and then pop it in 6th. Like I'd run 1-3 to the speed I'll be cruising at and put it to 6th and push the cc button. Also on the highway follow close to semis. Drafting really works. I find around 65 in my lt (just under 2krpm) when cruising on flat highways gets the best mpg. Ymmv.


**** you auto correct!

 

[sdgdf]

I drive the same way you do OP and I get 38 mpg mixed. 34-35 city and 42+ highway. I try to enter each gear at about 1800RPM which is the lowest the turbo partially spools, and the 1.4T has peak torque from 1800-5000RPM. The turbo is small and meant for low RPM efficiency, so I use heavy throttle spooling the turbo and shift at whatever RPM that leaves me at 1800 in the next gear. Usually like 3000-3500 for 1st-2nd, 3000 2nd-3rd, and lower from there, I think 5th-6th I shift at 2200-2400? And once cruising I use 4th for <40, 5th 40-55, and 6th for anything higher.

Also, all that depends on how slow people are going in front of me, slope, etc. If its barely taking any throttle to maintain speed in 4th at like 35 in city driving I might shift to 6th and cruise around at like idle. I use the gearing to control the power output that I need, always using the minimum, if that makes any sense.

And WOT at low RPM isn't bad, its actually one of the benefits of driving a manual vs. driving automatic. Fuel is delivered according to airflow, at low RPM the engine achieves max airflow with little throttle, so past a certain throttle position it doesn't add that much fuel. Now, some cars will adjust a/f very rich at max throttle and in that case you want heavy throttle but not to the floor. Basically heavy throttle at low RPM uses more of its available efficiency at that RPM. Lighter throttle, higher RPM uses less of the engine's available efficiency at that higher RPM, if that makes any sense. That, and the engine has to fight more frictional losses, rotational mass, etc, the higher RPM it runs. Lower isn't always better though, the engine shouldn't strain that much. Normally a little 1.4L like what's in the Sonic wouldn't have decent torque til 3k if it were N/A and if it were like that I'd shift at 4k-4500 every gear. The Sonic is awesome because it has excellent, efficient power from 1800-3k because of the turbo and that combined with the long gearing and low cruising RPM means it can consistently beat N/A 4-cylinders in MPG. I usually beat EPA mileage ratings and have a history of hypermiling in different cars.

 

[sdgdf]

Driving style certainly matters a lot, but my experience is the opposite of what you are reporting; I normally drive somewhat aggressively, and when I deliberately ease off and drive gently, I get much better mpg. I tested this one day, got a full load of friends and drove around the Dallas area in a mix of highway and city miles using most of a tank, driving normally, then repeated the route using gentle acceleration and keeping the speed at or under the limit; I used a third less gas on the second lap.

I was not watching my rpms at that time, nor have I really made a practice of doing so. Based on your report here, I would guess that the relationship between rpms and mpg is more complex than a simple "keep it low" plan; perhaps accelerating at too low an rpm level is as bad as cruising at too high of one. If your early shifting and skip shifting is putting too much of a load on the engine, perhaps your brother got better mpg simply by shifting at proper intervals and not lugging.

When I skip shift, it is because I am ready to cruise; I accelerate through first second third, at which point I am going highway speed and go directly to sixth, no longer accelerating. Meanwhile when I am driving more gently, I do the same thing, but shift earlier, and also pick up fourth on the way up... although rarely fifth, which strikes me as a useless gear.

Driving gently I also keep out of boost; when I am pushing it (which I normally do) the pedal goes down and the boost climbs. Gently, the boost gauge never goes postive.

I'd like to see you try some experiments to see if you can duplicate your brother's results, on the surface they do seem very interesting.

5th isn't useless if you live in the suburbs/boonies. A lot of my commute has a speed limit of 45 mph and its too hilly to stay in 6th. Generally if I can't cruise like 55+ and I'm not in city driving I'm cruising in 5th. 4th is also an overdrive gear and its good in the city when I have to go like 25-40.

 

[Swordsmith]

5th isn't useless if you live in the suburbs/boonies. A lot of my commute has a speed limit of 45 mph and its too hilly to stay in 6th. Generally if I can't cruise like 55+ and I'm not in city driving I'm cruising in 5th. 4th is also an overdrive gear and its good in the city when I have to go like 25-40.

I have overstated... I meant it is largely a useless gear for me. I agree that if stuck at lower speeds and particularly in hilly conditions there is a time when fifth is handy. But I am rarely in those conditions.

 

[Brad Ferrell]

True, I use fifth on the freeway for interchanges between highways. 6th is still geared too high, even in my RS, for the engine not to lag. Over than that, it's usually 1st, 2nd, 3rd, and then 6th for me. 4th I use on freeway when traffic slows to around 40. I'm getting 33mpg overall with minimum highway driving (20-30 miles per tank).

 

[mja]

This tank my DIC reads 47 mpg, half a tank down. Ive found the DIC is about 2mpg higher than the actual. I usually shift at 1500 rpm to get this type of mileage with a light and smooth throttle touch, and cruise control on the freeway at 55-60 mph. If I drive normally I'll average 35mpg on the DIC. If I drive somewhat aggressively I've never seen below 31 mpg. In fact I find it extremely difficult to get less than 30mpg...at that point cops are pretty attracted to my driving style. I drive about 60-70% highway miles.

Since the weather changes daily, from temperate to cold in Houston in the first few months of the year, I've noticed cold weather snaps decrease my mileage significantly. I did a little test last tank, drove 5-6 miles on the freeway at 60mph and the DIC read 70 something mpg. Ill find a pic later. If you drive it right it'll return far better than the mpg on the sticker. Im happy with my sonic mpg's.

I think skipping shifts and too much rpm, along with throttle input that may not be smooth enough, could all be hurting the mileage.

 

[mja]

Last tank was reading 50mpg on the DIC. Was 3/4 of the tank down... would've been my best tank yet. Then I got a tune and had to test it out :sadbanana: but more like :banana:

After filling up and getting on it after the tune, I netted 48mpg, hand calculated after 9.8 gallons, best so far.

 

[JWV]

My DIC will change by 0.1 MPG for every degree colder or warmer it is. Its like clockwork, as long as I have reset it somewhat recently. Last time I drove a long way I was on a 55mph road for about 70 miles. It had some small hills but finished it at 60mpg going 55mph. My car definitely gets better mileage now that I have over 20k miles on it.

 

[KiddParK]

I've recently moved over from my sport tune from Jerry to the MPG tune from Diablo sport and on long trips it really shows with a soild 45 mpg. Although I've only put about 200 miles on it the jury is still out. I don't have the crazY power of the BNR tune but I don't always need that and tuning only takes 5 min.