Dip in MPG starting in NOV

[RyanbabZ71]

Ok I got gas today and I was inputing it into my excel spreadsheet when I noticed something wierd. All of Aug-Oct I got 15-16mpg per fillup (50% city-50% highway). The past 3 fillups in Nov the highest MPG I have got is 13.9 mpg. The avg is about 13.5 mpg. HMMM i do about the same 50/50 driving. The winter oxygenated gasoline must have come out early this yr??? I swear if I was living somewhere other than this area I would be getting high mpg. While in NC last summer I was getting close to 20 for 2 weeks.

[Ben]

Why I reset the computers RAM twice a year when the reblend takes affect.

 

Ditto 1.5-2 MPG difference and most of it comes back after the reset. Not all, as there's less BTU's per with the MTBE or whatever they are using now.

 

Do it again in spring time.

 

Wonder how local EPA figers when to tell'm to reblend...

[RyanZ71]

I too have noticed a decrease in MPG and I attribute it to the winter blend of gas as my driving habbits have not changed.

[Shaners]

Your truck will run rich longer due to the colder temps. But the way I understand it, fuel is redone 4 times a year... (different blends). My gas MPG's suffer significantly in the winter due to my short trips... I probably lose 1.5-2.0 MPG's!!!

[01BlackZ71]

Two things:

 

1. I've never heard of anyone dedicated enough to create an Excel spreadsheet to track fuel mileage. I must admit though, that's a pretty good way to do it if you've got the time (and desire).

 

2. Please explain these different blends of gasoline? This is all new to me and sounds interesting.

 

Thanks.

[RyanbabZ71]

. I've never heard of anyone dedicated enough to create an Excel spreadsheet to track fuel mileage. I must admit though, that's a pretty good way to do it if you've got the time (and desire).

 

dedicated? its easy. I have it set up in columns (trip, total miles, gallons, mpg, price per gallon, total price. Plus I have all my oil change, maintanance, and part numbers on the same file as a tab). If you want a copy to see how I do it email me [email protected]. I use excel so much (school and work) it comes natural to me.

[JayMan]

RyanbabZ71: wow, somebody as anal-compulsive as I am about logging fuel and maintenance!

 

Actually, I've kept logs (Paper and, starting in 1990, with a spreadsheet) just to make tax time easier. I use my equipment for work and have had it with keeping recepits in an old shoe box

 

For some reason, my truck consistently gets 1-3 MPG more running Ethanol blend gas, also more power. In Canada, that would be from Mohawk or Husky. Might be the higher octane (90 versus 87) or maybe it just keeps the injectors and combustion chambers cleaner.

 

I don't think they will be using MTBE for much longer. There are driveability problems and maintenance issues. Doesn't this stuff actually contribute to smog? When I used to live in Salt Lake City, there was a big deal about MTBE contributing to the PM10 component of smog.

 

Ben mentioned resetting the PCM (Remove the negative cable for 10 minutes). That will force the PCM to make new fuel trim maps, and could improve your fuel economy.

 

Don't forget to do the Idle Learn Procedure or the reset procedure won't gain as much as it could.

[RyanZ71]

could you please explain what the "idle learn procedure" is and how to do it?

[RyanbabZ71]

have had it with keeping recepits in an old shoe box

 

I have every gas receipt since I have bought the truck (Apr 00). The old ones are in an envelope labeled by each year. My gf thinks i am nuts (i probably am but oh well)

[asepgrad98]

Do you let your truck warm up before you drive it when it is cold outside? could be an answer...

[RyanbabZ71]

No i havent because it hasnt been below 30 in the morning and i can see out of my windows so idling isnt the cause

[tmoreau]

I just noticed about a 2mpg drop in my last two tanks of gas. Thought something might be wrong.

 

I also keep a excell spreadsheet with detailed fuel logs since tank one, I input date, miles, gallons, total price and it gives me mpg and then sumarizes how many miles per year I am averaging, average miles per gallon, dollars per year and such. It probably took less than an hour to create and I keep it as a page in my checkbook spreadsheet.

 

Anyway, I average 17.7mpg usually get no less than 15.5 around town and 19-21 on the highway but I just got 14.5 which is next to my worst tank ever (13.5, 55-60mph fourth gear with a 5k lb trailer). I have been driving some backroads lately that are different from my normal driving habbits so I wasnt sure where the difference came from. At least now I know that there probably isnt anything wrong with my truck.

[JayMan]

RyanZ71: "Idle Learn Procedure"

 

Anytime you remove the battery or remove power to the PCM, it "forgets" its learned fuel trim maps and idle maps. So the PCM is forced to use the baseline fuel trim maps and idle maps.

 

If you change the plugs, clean out a dirty IAC or TB, or have the injectors cleaned, the idle may not be right. If you have to remove the IAC to clean the IAC passages, you MUST do the Idle Learn. Usually it will idle way too fast, or the idle may be rough. You then have to teach the PCM how to idle again.

 

This varies by motor and year. For my 2000 with Vortec 5.3, here is how you do the procedure:

 

Bring the motor to operating temp. Make sure all the accessories (Lights, A/C, radio, etc) are OFF. Put your foot on the brake and put it in Drive. Keep it in Drive at idle for 5 minutes. With your foot on the brake, shift into Park. Let it idle for 5 minutes. Take your foot off the brake and shut the motor off. Wait 30-60 secs and restart. The idle should be within spec, and your right foot should be ready to fall off.

[bummed-n-Md]

I have a spreadsheet on my PDA that I sync up with the main excel spreadsheet I keep for tracking fuel etc. Because I always have my PDA with me, it takes 30 seconds after each fill up to record milage, gallons and status of oil level.

 

Sync'ing up with my main sheet, takes the push of a button.

 

I too have all of my receipts for fuel, oil etc. I started keeping everyting when I was told by the dealership that 1 qt every 1200 miles was normal consumption. (no longer the case with my truck, at 40K has very little oil consumption)

[LARSONEM]

Is gas mileage something you are supposed to worry about? When the tank is empty it's time to fill it up or resort to tennis shoe transportation.

 

Something a lot of people forget about is the colder weather. PCM's change engine rpms to cause an engine to run at higher RPMs to get it warmed up. This in turn cuts emissions and air pollution in the long run. Another thing is cold fluids. Cold motor oil, transmission oil and gear lube can cause an engine to work harder until it gets warmed up. This in turn cuts fuel economy too. So it's really a lot more than the formulation of the fuel mixture.