Gas consumption

[95SevilleSLS]

Yes thats all city driving but when I say city I'm not talking Boston type stop and go, Wor pop 176,000. a mixture of driving but almost no highway. I'm still getting 13 avg and the more the gas prices keep going up the more the Cadillac stays parked and the new Nissan goes out. And thats a shame because I enjoy driving my STS pure luxury I love driving it. Maybe I need a tune up if people with the same car are telling me their getting 18-20 mpgs.

I did a tune up and I'm getting between 13-14 at best. I do let it warm up a bit though and most of my trips are less than 2 miles.

Do you let yours warm up much? That will make a huge difference. How far do you go before you shut it off usually?

[Peter1972]

Yes thats all city driving but when I say city I'm not talking Boston type stop and go, Wor pop 176,000. a mixture of driving but almost no highway. I'm still getting 13 avg and the more the gas prices keep going up the more the Cadillac stays parked and the new Nissan goes out. And thats a shame because I enjoy driving my STS pure luxury I love driving it. Maybe I need a tune up if people with the same car are telling me their getting 18-20 mpgs.

I did a tune up and I'm getting between 13-14 at best. I do let it warm up a bit though and most of my trips are less than 2 miles.

Do you let yours warm up much? That will make a huge difference. How far do you go before you shut it off usually?

I absolutely let all my vehicles warm up it's a habit growing up around the sand and gravel business where all the machines and trucks are always warmed up sometimes for an 1/2 hour or more. when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

[JasonA]

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

[95SevilleSLS]

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

Agreed. Gm says a maximum of 3 minutes if I remember right. If you're worried about damaging your cold engine, just drive nice and it will be ok. They warm up faster by driving them anyway. That's where all your fuel is going.

[Peter1972]

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

Agreed. Gm says a maximum of 3 minutes if I remember right. If you're worried about damaging your cold engine, just drive nice and it will be ok. They warm up faster by driving them anyway. That's where all your fuel is going.

Thanks guys it just seems to run rough for the first couple minutes so I probably do let it warm up to long old habits die hard. I think I'm prolonging the cars life the longer I let it warm up. Maybe not.

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

Agreed. Gm says a maximum of 3 minutes if I remember right. If you're worried about damaging your cold engine, just drive nice and it will be ok. They warm up faster by driving them anyway. That's where all your fuel is going.

Thanks guys it just seems to run rough for the first couple minutes so I probably do let it warm up to long old habits die hard. I think I'm prolonging the cars life the longer I let it warm up. Maybe not.

Also what about these people with the car starters in the winter they start the car 45 min before work so the heat is hot . people where I live do it all the time I had a brand new 96 F350 back then with a 460 motor and used to let it warm up for about a half hour in the winter but the gas was much cheaper then nice and toast warm. Also you have to understand I'm a truck driver and I let the truck Idle all night long while I'm in the sleeper I love the rumble of the motor it puts me right to sleep.

[95SevilleSLS]

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

Agreed. Gm says a maximum of 3 minutes if I remember right. If you're worried about damaging your cold engine, just drive nice and it will be ok. They warm up faster by driving them anyway. That's where all your fuel is going.

Thanks guys it just seems to run rough for the first couple minutes so I probably do let it warm up to long old habits die hard. I think I'm prolonging the cars life the longer I let it warm up. Maybe not.

when it's real cold 10 degrees or so I will let the STS warm up for 15 Min's or more. now that we are getting into spring I let it warm up about 5 min.

That's way, way, WAY too long, no matter the outside temperature. These cars do not need a warm-up period...not like that anyway. Not only are you using fuel sitting there idling the car, but you're also really contaminating the oil with that raw gasoline (the car runs very rich when idling cold like that).

Get in it, start it, let it idle for 30 seconds if you want to, but just drive it man! That's the cause of your poor fuel economy, and it's totally and completely unnecessary. Really.

Agreed. Gm says a maximum of 3 minutes if I remember right. If you're worried about damaging your cold engine, just drive nice and it will be ok. They warm up faster by driving them anyway. That's where all your fuel is going.

Thanks guys it just seems to run rough for the first couple minutes so I probably do let it warm up to long old habits die hard. I think I'm prolonging the cars life the longer I let it warm up. Maybe not.

Also what about these people with the car starters in the winter they start the car 45 min before work so the heat is hot . people where I live do it all the time I had a brand new 96 F350 back then with a 460 motor and used to let it warm up for about a half hour in the winter but the gas was much cheaper then nice and toast warm. Also you have to understand I'm a truck driver and I let the truck Idle all night long while I'm in the sleeper I love the rumble of the motor it puts me right to sleep.

I have remote start, but I still don't let it warm up that long. In extreme cold (-20) I let it warm up 5 minutes MAYBE 10. Letting it sit and idle is worse than driving it nice to warm up. You'll get carbon buildup by letting sit and ilde and it will take 2-3 times as long to warm up idling than driving. People that start it, don't let it warm up and drive with their foots in the floorboards are the ones that are hurting their engines. It's just not a good idea to let things warm up that long, diesels are a different story. And fords, don't let them warm up and they'll fall apart!

[JimD]

The whole concept of 'warm-up' with a modern engine is just not required as far as the engine is concerned. People comfort is a different issue and I can identify with not wanting to put your backside down on a cold leather seat. GM and others offer you heated seats (and steering wheels) to pamper the body parts.

Start the engine, put the thing in gear, and drive on down the road. The PCM will take care of the engine. This is the 21st century, folks; digital controls operating at the speed of light.

[95SevilleSLS]

The whole concept of 'warm-up' with a modern engine is just not required as far as the engine is concerned. People comfort is a different issue and I can identify with not wanting to put your backside down on a cold leather seat. GM and others offer you heated seats (and steering wheels) to pamper the body parts.

Start the engine, put the thing in gear, and drive on down the road. The PCM will take care of the engine. This is the 21st century, folks; digital controls operating at the speed of light.

Amen!

[Peter1972]

The whole concept of 'warm-up' with a modern engine is just not required as far as the engine is concerned. People comfort is a different issue and I can identify with not wanting to put your backside down on a cold leather seat. GM and others offer you heated seats (and steering wheels) to pamper the body parts.

Start the engine, put the thing in gear, and drive on down the road. The PCM will take care of the engine. This is the 21st century, folks; digital controls operating at the speed of light.

Amen!

Alright I'm going to start it and drive it and see if the Mpgs improve. Thanks

[Bruce Nunnally]

Not to be too obvious, but also reset the avg mpg so that you know where you are measuring from.

[95SevilleSLS]

Not to be too obvious, but also reset the avg mpg so that you know where you are measuring from.

Yep. I'm reset that and I do it the old fashioned way by filling it up at the same pump and dividing the miles by the gallons...I think I said that right

[JimD]

One more time: the DIC display of MPG INST and MPG AVG are more accurate than trying to fill the tank to exactly the same place every time.

[Peter1972]

One more time: the DIC display of MPG INST and MPG AVG are more accurate than trying to fill the tank to exactly the same place every time.

which is a more accurate method do you think and the reason why? Thanks I'm beginning not to trust the cars computer seeing that some people with the same car and claiming 18 to 20 mpgs with the same around town driving.

[BodybyFisher]

Peter, here is a thread that got into how the on-board fuel metering and monitoring works:

http://caddyinfo.ipbhost.com/index.php?sho...;hl=pulse+width

[JimD]

The PCM wins hands down in terms of accuracy and consistent repeatability.

To oversimplify it, all the PCM has to do is add up all the injector pulses, convert that to volume of fuel delivered, and divide that into the distance driven. Since the PCM is controlling the injectors, the PCM knows how many times the injectors are pulsed open (total engine revolutions), and how many microseconds the injector was held open (pulse width). If an injector flows X amount of fuel in Y microseconds at Z fuel pressure, the rest of the math is easy.

The big variable in the filling the tank method is --when is the tank full? When the pump shuts off? When your hands are too cold? When you are too wet to stand there and fiddle with the pump handle any longer?

Over the long term, the difference between PCM calculations and how much fuel you actually put in the tank might be small. But there is no doubt in my mind which method is more accurate and consistent. To take it to the extreme, I keep a spreadsheet on everything I do to my cars. For the first 152,000 miles, the difference between the DIC display and gas station pump is 5%.

People claiming fuel mileage could be anything. Different drivers in different situations and conditions.

[95SevilleSLS]

One more time: the DIC display of MPG INST and MPG AVG are more accurate than trying to fill the tank to exactly the same place every time.

I know, I know! That's about the 3rd time someone told me that! I was just saying I'm going to do BOTH. I want to compare them. There's no need to lecture me. Shoot me if I'm old fashioned, I just have troubles trusting electronics. Like I said though, I'm just comparing the two.

[JimD]

....I just have troubles trusting electronics.

That has to be more than a little bit inconvenient in the 21st century

[95SevilleSLS]

....I just have troubles trusting electronics.

That has to be more than a little bit inconvenient in the 21st century

Oh trust me, it is!

If they still made carb. engines, I'd probably still buy them!

[BodybyFisher]

THEN, if you had a carburator, you could WARM your car up, like you like to do!!!

[95SevilleSLS]

THEN, if you had a carburator, you could WARM your car up, like you like to do!!!

You're right!

[Peter1972]

The PCM wins hands down in terms of accuracy and consistent repeatability.

To oversimplify it, all the PCM has to do is add up all the injector pulses, convert that to volume of fuel delivered, and divide that into the distance driven. Since the PCM is controlling the injectors, the PCM knows how many times the injectors are pulsed open (total engine revolutions), and how many microseconds the injector was held open (pulse width). If an injector flows X amount of fuel in Y microseconds at Z fuel pressure, the rest of the math is easy.

The big variable in the filling the tank method is --when is the tank full? When the pump shuts off? When your hands are too cold? When you are too wet to stand there and fiddle with the pump handle any longer?

Over the long term, the difference between PCM calculations and how much fuel you actually put in the tank might be small. But there is no doubt in my mind which method is more accurate and consistent. To take it to the extreme, I keep a spreadsheet on everything I do to my cars. For the first 152,000 miles, the difference between the DIC display and gas station pump is 5%.

People claiming fuel mileage could be anything. Different drivers in different situations and conditions.

I wanted and explanation and I guess I got one I never knew that it went by injector pulses thats incredable I appreciate you taking the time to explain. Thank you

[Peter1972]

I don't want to beat a dead horse and I've cut down on my warm up times considerable due to recommendations from this thread. But I still have it in my head that when you let a engine warm up any engine and let the oil viscosity thin out when it's cold that you are prolonging that engines life. If I was getting chased by the devil even would I ever get into a cold car start it up throw it in drive and go. It has been drilled into my head from the time I was little to let engines warm up.

A few replies back I remember someone saying that by excessive idling is causing raw fuel to contaminate the crankcase oil. In today's engines how would this be possible why wouldn't there be full combustion at any RPM. I'm just asking because I don't know I'm not necessarily disagreeing.

[KHE]

By letting the car idle excessively, you're loading the crankcase with blowby and moisture. The Northstar engine heats up very quickly. Just start it and drive away - don't hammer it until the temp gage indicates the optimum temp. and you will be fine.

The best way to rid the crankcase of moisture is to get the oil hot - by driving it, not by idling it.

[Ranger]

I still have it in my head that when you let a engine warm up any engine and let the oil viscosity thin out when it's cold that you are prolonging that engines life. If I was getting chased by the devil even would I ever get into a cold car start it up throw it in drive and go. It has been drilled into my head from the time I was little to let engines warm up.

I was the same way Peter, but that is old school carburetor thinking. Old habits die hard. Now I just start and go. I do go easy on her when she is cold. Never had a problem with engine life or any other related problem for that matter.

[95SevilleSLS]

I still have it in my head that when you let a engine warm up any engine and let the oil viscosity thin out when it's cold that you are prolonging that engines life. If I was getting chased by the devil even would I ever get into a cold car start it up throw it in drive and go. It has been drilled into my head from the time I was little to let engines warm up.

I was the same way Peter, but that is old school carburetor thinking. Old habits die hard. Now I just start and go. I do go easy on her when she is cold. Never had a problem with engine life or any other related problem for that matter.

I was actually that way to up until I switched over to GM and found out that was a no no.