Confounding Mileage Problem - Need Advice

[wdenny]

Gentleman, (and ladies)

First let me say that I am new to the forum and everything I have read thus far is superb. I am really excited to be able to join and get to communicate with you.

I am having some trouble with the mileage on my 2004 Matrix XR. When the temperature is low, my milieage drops. Now, I know that this is to be expected with all vehicles, but I don't see how it should be this extreme in my case. I always data log my car. By that I mean, everytime I fill up I log miles, gallons, price, mpg, avg fuel cost, temperature, driving conditions etc. I keep all of this in a spreadsheet to keep track of trends for preventative maintenance and also because, I'm a huge nerd. But that is another subject. I have noticed, that my cars mileage drops, almost more than 20% when the temperature gets in the 32 degree range. This is reqaurdless of preheating (warming up) or not. In the winter at temperatures below 32 degrees, I am holding steady at about 27 to 29 mpg. However, in the summer in temperatures of over 55 to 90 degrees, I can acheive over 36 to 37 mpg. Following is a list of variables that I have eliminated:

Mobil1 oil and filter changed every 3Kmi (NO EXCEPTIONS)
K&N Air Filter
Good Tires
Good Driving Habits (Slow acceleration, varying speed for incline etc.)
Recurring Conditions - I drive the same road the same path EVERY DAY (170 Miles round trip)
Same Fuel Supplier (although I am aware that gas has seasonal properties)

Now, if I were a normal driver, this wouldn't be such a big deal to me. However, I drive about 900 miles a week. So, 20 percent is a huge deal to me at these gas prices. I have heard all kinds of stories about why this happens. The main one I have heard, and tend to want to believe, is the temperature of the transmission. However, I have no evidence to back that up. If that is the case, I am more than happy to rectify the problem with a heater or monitor it with a MCU and some RTD's to see what the deal is.

I just though maybe you all had some insight to something that I hadn't though of, or heard of regarding this aggravation.

Thanks,

[toyomoho]

Is this a winter/summer issue or does the mileage drop consistently only at cold temps regardless of time of year?

Next time at the fuel pump check to see if the fuel contains alcohol or some other additive during the winter months.

Often localities will mandate gasoline sold during the winter to contain 10% alcohol or some other additive. In some places the fuel is called oxygenated. This fuel mix is supposed to lower air pollution. Some localities now require full time use of this fuel.

This fuel blend will lower MPG by about the amount you are experiencing.

If using the same non-blended fuel year round, the engine computer system should adjust the fuel flow to compensate for air temp. All things being equal a 20% drop just based on air temp would indicate something is wrong with the cars systems.

If an automatic, the fluid will come up to temp winter or summer by means of the fluid cooler in the radiator. If a manual, the fluid will heat up on its own after a few miles unless the temps are extremely cold.

[wdenny]

Well, after picking the brains of some other car guys and a former professor of thermodynamics, here is the conclusion that I have come too. There are basically three things going on.

1) Cold air (below freezing), facilitates condensation (reformations of liquid) of fuel vapor in the cylinder to the extreme that it require more fuel to run. (Thanks to the ECU).

2) Cold fuel (close to or below freezing) has the same problem as above being more difficult to vaporize.

3) Cold transmission fluid (close to or below freezing) is less viscous and therefore produces more friction, i.e. requires more power/fuel to run at the same output.

It sounds to me, like all of these problems could be solved with some heat. A fuel pre-heater, an air pre-heater, and a trans warmer.

Anyone see any fatal flaws thus far?

[tgidavid]

I'm not sure how it is in your part of the country, but the gas companies change the fuel blending for summer and winter. I've noticed MPG differences for those seasons even more so now that MTB has been banned.

[Smar969905]

i have heard of fuel warmers for diesels, so if nothing else, you could get one of those and install it. there are likely some that are made for gas, but i dont know for sure. the cold air shouldn't be such a problem. people install cold air intakes for the purpose of running colder air into the motor so it is denser for more power. my suggestion for you for now would be to only do the fuel warmer. if you wanted to get more in depth, you could probably find a way to get the coolant to go through some customized piping that wraps the transmission, but that wouldn't help out until the car has warmed up. that would also be quite expensive.

[kevintomb]

HOLY CRAP 36-37 MPG?? I never get number approaching that with my 03 base matrix....do you have an automatic as I do? Heck in colder weather I usually get somewhere around 21-24 MPG.....I know thats a short work drive, but I see that matrix cars have widely varying gas mileage accounts...on a trip that is almost all highway miles I barely get over 33 mpg ever. So im kinda interested in HOW you are able to get 36-37 MPG or is there something wrong with my car??

and before anyone says..driving habits....etc..im talking regular highway driving 65 mph and no fast accelerating...just REGULAR cruising....honestly your winter mileage is VERY good.

[wdenny]

I hope I am not breaking any forum rules here, posting a reply I got from another trixer on another forum, but he is getting 40-46mpg on his with the following mods. I am looking to duplicate.

Let me know if I need to document this better, not trying to pirate or anything.

slimreynolds (matrixowners.com)
"I've the same model as you, 04 XR. As you can see in the picture I've got the front end blocked up except a small opening above the license plate. I try to keep the water temp at 210-220. The 1zz engine is very efficient at these temps. Also in the pic I have very small side mirrors for better aero. I run 50 psi in the tire. I use amsoil 0w30 oil and amsoil gear oil. I also took the back seats out to lighten up a little. I have K&n air filter, megan axle back exhaust for engine to breath better. I also add 3 ounces of this mixture per 10 gallons of fuel, or 4 ounces when I fill up when tank is close to empty. 3 parts acetone, one part xylene, and one part lucas oil upper cylinder lubricant. It only adds a few cents per gallon of gas but it will give you a pretty good boost in FE, especially in the summer. The last thing I did was add a device called an electronic fuel injection enhance which add voltage to the o2 sensor leaning out the fuel mixture. You are an electrical engineer so I think I don't need to explain how it works. If you do these mods separately you won't see a big FE gain but together you will see gas mileage like mine. I would also suggest a scangauge. I now have 285k miles on my car and I am getting the best gas mileage I've seen. The biggest thing that helps out your FE is driving style. Slow down a bit, coast to red lights and down hills. A scangauge will help you out with this big time. Hope this helps."

[kevintomb]

Originally Posted by wdenny

I hope I am not breaking any forum rules here, posting a reply I got from another trixer on another forum, but he is getting 40-46mpg on his with the following mods. I am looking to duplicate.

Let me know if I need to document this better, not trying to pirate or anything.

slimreynolds (matrixowners.com)
"I've the same model as you, 04 XR. As you can see in the picture I've got the front end blocked up except a small opening above the license plate. I try to keep the water temp at 210-220. The 1zz engine is very efficient at these temps. Also in the pic I have very small side mirrors for better aero. I run 50 psi in the tire. I use amsoil 0w30 oil and amsoil gear oil. I also took the back seats out to lighten up a little. I have K&n air filter, megan axle back exhaust for engine to breath better. I also add 3 ounces of this mixture per 10 gallons of fuel, or 4 ounces when I fill up when tank is close to empty. 3 parts acetone, one part xylene, and one part lucas oil upper cylinder lubricant. It only adds a few cents per gallon of gas but it will give you a pretty good boost in FE, especially in the summer. The last thing I did was add a device called an electronic fuel injection enhance which add voltage to the o2 sensor leaning out the fuel mixture. You are an electrical engineer so I think I don't need to explain how it works. If you do these mods separately you won't see a big FE gain but together you will see gas mileage like mine. I would also suggest a scangauge. I now have 285k miles on my car and I am getting the best gas mileage I've seen. The biggest thing that helps out your FE is driving style. Slow down a bit, coast to red lights and down hills. A scangauge will help you out with this big time. Hope this helps."

I would be VERY dubious of outrageous claims of HIGH mileage. Running 50lbs of air in the tires alone is dangerous and would wear the centers of the tires out REALLY quickly, first off. Chaning the mirrors and blocking the front would have VERY minor aerodynamic changes. The engine mods would also display VERY small increases in mileage as would removing the rear seat...it only weighs about, what, uh 50 lbs, that would make almost NO difference. The stuff he adds to his engine...uh im not sure what that does or what it would damage. All together im sure his mods all add up to a small increase, but if it was that easy, toyota would have implemented these ideas and advertised the matrix as the perfect crossover vehicle that regularly gets over 40MPG.....in other words, if a MAJOR car manufacturer didnt think to do this stuff, it PROBABLY wasnt necessary, or useful.

[redpilot13]

Hey folks,
I'm having the same problem with my Matrix. Poor numbers with the fuel economy. I just bought my car in November 2007 and right from day one I've been getting worse numbers than my old 1988 Camry 2.0L Automatic. My average right now is 10L/100Km or 23.5 MPG (U.S GAL). Now, I know it could be just the cold weather or the snow tires or the crappy 10% Ethanol blend that they are forcing upon us at every gas station now, but all factors considered I think I should be getting better economy than that. This car sure does not live up to the EPA ratings.

I know that my car is 4 years old, so I'm on a rampage right now just to figure out what is wearing out and needs replacing.

I found a fuel economy checklist from a magazine (don't remember which one) a long time ago and saved it.

I will repost here. I hope it helps.

For Better Fuel Economy
1. Check and change Air Filter
2. Change PCV valve - should hear a rattle if you shake it, or feel a suction when engine running
3. Change spark plugs - I don't trust Platinum or Iridium claims to last longer because what really wears out is the ceramic! Not so much the electrode!
4. Change plug wires - these dramatically improve fuel economy - but not really applicable to the Matrix
5. Check Distributor Cap & Rotor - not applicable to Matrix
6. Check and change Fuel Filter
7. Use synthetic oil (engine and transmission)
8. Make sure you have proper tire inflation
9. Don't race - drive at a steady pace


Other good monthly checks not related to fuel economy:
1. Check Brake Fluid - should not be coffee brown/black
2. Check Transmission Fluid - should be red
3. Check Engine Oil
4. Check Washer Fluid
5. Check Coolant
6. Check Hoses - should be flexible - not hard & brittle
7. Check Belts - both sides - check tightness - no more than 1" deflection
8. Check Battery - clean terminals - apply silicone grease
9. Check Tire Pressures - including spare

Well that's all for now. I hope this helps out. I plan on checking all the items in the fuel economy list and hopefully I will solve this problem.

Cheers!