Gas Mileage

[tiybe]

Are there any idea's on how to get better gas mileage from a 2003 Pontiac Sunfire?  Thanks 

[Professur]

Overinflate your tires, empty the trunk, do a full tuneup, and drive with a light right foot.

 

If you suspect you have a problem, start by checking your compression. If the compression is low, Bandaid upgrades are just a waste of money. That motor is very unforgiving over lax oil changes.

Edited January 11, 2017 by Professur

[tiybe]

Thank you sir, car seems to be running fine. I've heard from plenty of people that these cars don't really get great gas milage, even when new. 

[Professur]

The missus has that same POS in a 2005 Malibu. You think you've got it bad.

[Frosty]

12 hours ago, tiybe said:

Thank you sir, car seems to be running fine. I've heard from plenty of people that these cars don't really get great gas milage, even when new. 

The EPA rated these cars at 25 mpg city and 33 highway...."your mileage may vary"!

[Professur]

Forget an oil change or two and that swiftly drops .. I'm averaging 12mpg city. The big wagon gets better even with having to leave the carb warm up for 5 minutes.

[tiybe]

Realy eh?  Yea I think my 1988 Caprice gets better gas mileage 

[Last Indian]

While I believe the consensus is the Sunfire doesn’t get great fuel economy there is a reason, and it's not that car specifically! The problem is an EPA illusion created by saying that fuel mileage today is better, not true! As a general statement not a specific one! Fuel economy for the auto industry today versus say 40 years ago, when compared to engine/transmission configuration and outputs, versus body configuration I.E. weight, tire configuration etc… Has not changed much at all! Your Sunfire when compared to a Vega 3 door as an example is close to the same configuration. Likewise so is the fuel economy. In 1967 I owned a 67 Impala, a 283 with a powerglide tranny. It got 18-21 mpg. Today I own a Buick LaCrosse with 3.6 with a 6 speed tranny, it gets 18-21 mpg both cars are relatively comparable in weight and wheelbase. Other specs like tire size etc. aren’t. 
Without getting real complicated the total power band configuration of the V8 and powergluide match that of a V6 and a 6 speed trans when compared to body configurations. Some, not many, but some newer technologies like DIC have helped improved fuel economy. The end result is for the Sunfire to get noticeably better fuel economy you would need to reduce weight or actually increase cubic inch displacement, not hp, but displacement.

 

[tiybe]

Thanks for taking the time to explain, understood 👍👊

[Frosty]

Another point to add is that is torque, not horsepower, that gets you down the road. So to add to what Last Indian stated, adding displacement will add both horsepower and torque by increasing cubic inch displacement. However, it is torque, or the rotation force, that actually moves a vehicle. There are several examples were a low horsepower but high torque engines are more desirable for street application, this is particularly true in the trucking industries.

Case in point, back in the early 1960s, GMC had a 305 CI V6 engine is used in its light duty pickups. They also built what they called the Twin Six, a V12 710 CI engine (essentially two 305 V6 back-to-back) that they used in medium and heavy duty trucks. Some even pulled Minute Man Missiles. The Twin Six produced less than 200 HP, but it had enough torque to move a missile! Let's see a modern V12 do that.

GMC Twin Six V12 engine

[Professur]

I wonder if I could get that under the hood of the parisienne .....

[Ringo64]

20 minutes ago, Professur said:

I wonder if I could get that under the hood of the parisienne .....

 twist the frame a bit

[Professur]

Four and a half foot long ... might have to go with an electric fan and water pump. I hate electrics.

[Last Indian]

One bit of advice that may or may not help minimally with mpg, but well definitely help wth performance and continued maintenance of the fuel/induction system is to use a fuel additive that has PEA (polyether amine)in it such as Regain by Gumout. PEA is the highest end fuel additive there is and will cleanup many deposits and varnish that other additives won’t. All fuel injected engines suffer from the same issue which is that no fuel flows past certain components. Port injection is a problem, but DIC is the worst as it gets no fuel to the back of the intake valves. Either way deposits and varnish buildup is a problem in fuel injection systems. I can tell you factually that PEA works as I spent three years developing systems to deliver it for OEM use for warranty issues as well as a advisory role in the development of the chemistry.

[notallthere]

Just out of curiosity what are you getting on your Sunfire?  My wife has an 04 Cavalier and mixed driving we are averaging 29-31 mpg.

[tiybe]

400KM per fill up 

[tiybe]

Hey, I thought some new tires might help 

[notallthere]

Based on that you are averaging about 19-22 mpg.  Unless you are idling your car constantly then you mileage is way low.  The first place I would look at are your O2 sensors as worn ones might not throw a code but would richen up the fuel.

[tiybe]

On 1/13/2017 at 7:12 PM, Last Indian said:

One bit of advice that may or may not help minimally with mpg, but well definitely help wth performance and continued maintenance of the fuel/induction system is to use a fuel additive that has PEA (polyether amine)in it such as Regain by Gumout. PEA is the highest end fuel additive there is and will cleanup many deposits and varnish that other additives won’t. All fuel injected engines suffer from the same issue which is that no fuel flows past certain components. Port injection is a problem, but DIC is the worst as it gets no fuel to the back of the intake valves. Either way deposits and varnish buildup is a problem in fuel injection systems. I can tell you factually that PEA works as I spent three years developing systems to deliver it for OEM use for warranty issues as well as a advisory role in the development of the chemistry.

well, I got me some of this. Hopefully it helps 

13 hours ago, notallthere said:

Based on that you are averaging about 19-22 mpg.  Unless you are idling your car constantly then you mileage is way low.  The first place I would look at are your O2 sensors as worn ones might not throw a code but would richen up the fuel.

Thanks ☺

[tiybe]

Well, after adding additive and changing the spark plugs, two of which, had no diode left, am now getting 15 more km. from a fill up.

[Professur]

Better than a kick in the teeth.

[tiybe]

33 minutes ago, Professur said:

Better than a kick in the teeth.

True,True. Next I'm going to replace the O2 sensor 

[Frosty]

One thing you haven't mentioned is the mileage on the odometer. If you have high miles/kilometers, then you might need to replace your spark plug wires or even the coil packs. I would consider removing the throttle body and doing a thorough cleaning of it with carburetor cleaner as varnish tends to build up on the throttle body plate over time.

Check you owners manual for when plug wires and coil packs should be replaced.

The O2 sensor replacement is still a good idea in my book too.

Edited January 30, 2017 by Frosty

[Professur]

Um, be careful with that throttle body. I've heard tell that spraying cleaner down it can bugger the TPS.

[Frosty]

If that worries you, you can remove the sensor before cleaning it.