biglg

I always have heard that the cooler a vehicle runs the better the fuel mileage should be?

fredster

Yes...with the right calibration to take advantage of it, colder air is denser and should result in a more complete burn. But this is more for horsepower than MPG. Still, with the advancements in engine calibrations I would hope that 10-20 degree change in air temperature would not cause an 15% drop in fuel economy.....

tahoe07

Just a thought but did you check your tire pressure lately? Temperature drop equals less pressure and more rolling resistance. Tires tend to loose air any how and then you add the drop in Temp. Could be a contributing factor[sm=smiley25.gif]

73shark

No heater! Diesels have heaters because diesel fuel tends to gel at cold temps.

Have you checked with your service dept?

fredster

I'll be at 5K miles within a week and then the Tahoe goes in for an oil change and door window trim replacement. I will also relay my story about the extremely variable mileage and ask them to do what they can or possibly give me the "official GM explanation" about the MPG.

They also need to look at the charging system as my voltmeter tends to vary from 14 volts all the way down to 12 and then to various places in between as I drive.

BTW...I DO understand why a diesel needs a fuel heater, but the comment was made that warm fuel is more dense so I couldn't resist making a semi-sarcastic remark.....my dark side coming out I guess.....

I will post what service tells me about the MPG's if they actually have anything to say other than "normal operation".

jasonw75

Fredster:

There is nothing wrong with your charging system. I thought the same thing, however I asked the question on here and was informed by a reliable source that this is quite normal. Your vehicle shuts down the charging system when it isn't in use. This allows your engine to produce more horsepower and run more efficiently when the alternator is not engaged. You will also notice you have electric fans on the radiator for the same reason.

Jason

digdug

Hey Jason. What prompted you to ask that question 'cause on mine sometimes it seems I will get a surge and the headlights lights will dim for a split second and then go back to normal. It happend once with my wife in the car and I pointed it out to her and she thought I was imagining things.

On another note, and you'll know what I'm talking about .. .no hard feelings, I was having a horrible week. Had to get that off my chest. I felt pretty bad.

~digdug

jasonw75

Dig:

I just noticed my volt meter going up and down the same way Fredster did. I've never noticed the lights dimming or getting brighter. Not to say this doesn't happen in my car as I'm normally the idiot driving down the road eating a sandwich and talking on the phone while adjusting my radio.

On the other note, no worries, I'm not one to hold a grudge at all. I kinda talk out of my *** sometimes so I prolly deserved it.

Jason

digdug

Totally off topic but while I have you Michigan boys in one place ...

GO BUCKS!!!!

~digdug

jasonw75

Allright Dig, Now I'm upset. I was just starting to like you again and you had to ruin it.