[DonRSD]

is there anything i can do to increase my MPGs?

i drive maybe 10 miles a day (to and from work) but my MPG is super low.
all city driving.....well it isnt NYC just stop and go for a few lights

mind you im in south florida, so i havent even turned on the ac or heater since december

ive had the caddy since aug 2009 and havent change one filter or anything.

someone please give me some tips or if i need to replace anything.

thanks in advance gentlemen!!!

 

[Submariner409]

Not much you can do - even in Florida the car never gets a chance to warm up in 10 miles - just because the temp gauge is at 12:00 doesn't mean that the engine and transmission are ready to RUN. After only 10 miles your engine oil is still cool - not cold - cool. I'd bet that, at an ambient temp of 65 degrees, at the end of 10 miles the thermostat is not yet fully open.

The best maintenance you could do on your car is to take it on a 75 mile run once a week - and I mean RUN. Before you go, dump a 20 oz. jug of Chevron TECHRON fuel system cleaner into a tank of Top Tier 93 octane gasoline. (??? - Google)

Since August of 2009 have you driven 12,000 miles ? If so, you're past due for an air filter. WIX, PartsMaster, AC Delco, FRAM - stay away from K&N. How many miles on the engine ??? 100,000 is spark plug time. read the owner's manual Maintenance schedule.

 

[DonRSD]

Not much you can do - even in Florida the car never gets a chance to warm up in 10 miles - just because the temp gauge is at 12:00 doesn't mean that the engine and transmission are ready to RUN. After only 10 miles your engine oil is still cool - not cold - cool. I'd bet that, at an ambient temp of 65 degrees, at the end of 10 miles the thermostat is not yet fully open.

The best maintenance you could do on your car is to take it on a 75 mile run once a week - and I mean RUN. Before you go, dump a 20 oz. jug of Chevron TECHRON fuel system cleaner into a tank of Top Tier 93 octane gasoline. (??? - Google)

Since August of 2009 have you driven 12,000 miles ? If so, you're past due for an air filter. WIX, PartsMaster, AC Delco, FRAM - stay away from K&N. How many miles on the engine ??? 100,000 is spark plug time. read the owner's manual Maintenance schedule.

aug 2009 = 56k miles on the car

feb 2010 = new engine warrantied in.
i have maybe 10k on this new engine since feb 2010

will an air filter make THAT much of a difference?
i know i should get one, but should i also be expecting great results from my mpg?

 

[RippyPartsDept]

you should do an oil change at least once a year... even if the oil life monitor hasn't gone down to zero percent ... the recommended oil change frequency is once a year or when the OLM hits zero percent (whichever one happens first)

 

[baller95]

Since August of 2009 have you driven 12,000 miles ? If so, you're past due for an air filter. WIX, PartsMaster, AC Delco, FRAM - stay away from K&N. How many miles on the engine ??? 100,000 is spark plug time. read the owner's manual Maintenance schedule.

Why stay away from K&N i was planning to replace a K&N on my 2000 DTS !

 

[RippyPartsDept]

K&N that isn't properly oiled will either let more dust through due to not enough oil or screw up your MAF sensor due to too much oil

when the acdelco filter is under $20 at a dealership and around $10 online you have no reason to get a fancy K&N filter that might cause problems

 

[Freakzilla]

Replace the Cadillac with a Honda if you want better city milage.

 

[Ranger]

will an air filter make THAT much of a difference?
i know i should get one, but should i also be expecting great results from my mpg?

No..

 

[Bowler807]

Submariner409 is right on point. Let me expound somewhat and maybe it will make more sense. When the engine is cold it is running in an open loop situation. This creates an enriched fuel mixture until the engine warms up at which time the O2 sensors become active and the computer switches to a closed loop situation. One can compare this to the choke on a carburetor. When cold the choke closes enriching the fuel mixture and as the engine warms up, the choke releases.

In 10 miles you are probably in closed loop, but you haven't been there for very long. This coupled with all the fluids being "cold" which requires more power to cause them to flow will certainly reduce mileage significantly.

 

[DonRSD]

you should do an oil change at least once a year... even if the oil life monitor hasn't gone down to zero percent ... the recommended oil change frequency is once a year or when the OLM hits zero percent (whichever one happens first)

once a year?
that doesnt sound right.

 

[Ranger]

"Once a year" OR when the OLM tells you to, whichever comes first.

 

[Submariner409]

"Once a year" OR when the OLM tells you to, whichever comes first.

It was 70 here yesterday. Took the car for a run, came back and did the oil and filter in the garage. 11.5 months on the oil, OLM at 57%. Pennzoil Platinum 5W-30 and a WIX 51522. The drain oil was clear dark amber - you could see right through the stream. Mostly suburban/rural/highway miles. The fuel use, long-term (2 years since reset), is at 20.4 mpg and I'm getting just over 5,000 miles to a quart of oil. I have every fuel and oil receipt since I bought the car, and even on paper the figures hold up.

 

[Ranger]

You know, I'm now in that club Sub. Now that I am retired I don't put anywhere near the miles on that I used to and will probably be doing oil changes once every spring. I never really understood the one year thing though. Oil doesn't "go bad" and you don't use up (or wear out) the additives when not in use. :hmm:

 

[Submariner409]

I hear ya'.........The snake oil, old wives' tales, and advertising hype from the Oil Doodle shops lives on. I absolutely, positively detest "oil wars" but the sheer amount of gross stupidity and misinformation surrounding lube oils and various types of filters is hard to believe in this world of instant internet information. The constant question of "What oil is best for my Flapfish 357 ?" says the poster has never read the owner's manual, never researched 300 posts in CF, and has never learned to Google.

Modern automotive lube oil is some pretty magical stuff. PCV has eliminated a major source of lube oil pollution. Coolant temps at about the 200 degree mark positively lengthen oil life. Rapid coolant warmup time is also a significant oil life plus factor. Modern bearing and cylinder wall finishes coupled with low tension piston rings significantly reduces the amount of tin and iron scuffed into the lube oil. "Sludge" is reduced to a buzzword which fuels paranoia in those who believe advertising hype - to the benefit of the Oil Doodle.

Good ol' Kendall SAE 30 - "The 2,000 mile oil". (The Kendall two-finger salute)

 

[DonRSD]

Well I filled up yesterday and drove all highway miles. Each was was 55 miles.

I did about 75mph the entire time, each way.

My mpg readout was 21mpg for the entire round trip. Does that sound right?

Sent from my rooted Sprint EVO running Myn RLS 5

 

[Submariner409]

2002 DTS - at 75 mph you're turning 2350 - 2400 rpm. I would expect to see 22 - 23 mpg under those conditions. 24+ at 60/65 - 2,000 rpm or so.

For comparison my STS, same engine/transmission as yours, in Florida gives 24.7 mpg on I-95 at the same speeds. I never reset my fuel mileage readout - up here in MD it's sitting at 20.5; I do mostly suburban/rural driving with an occasional sprint to Norfolk, 213 miles one way. After one of those the mileage goes to about 22 or so - the 24.7 would show during a run to Gainesville.

Did you reset the long-term fuel mileage readout and let it start from scratch or were you using the instant readout ? I still believe that you need to look at the air filter and while you're at it, check the tightness of the large clamps on the air intake ducting. Do the Chevron TECHRON fuel system cleaning. It might help and it certainly won't hurt. Also, what air pressure do you carry in the tires, cold ? If you're at 30 or 28, a change to 32-33 psi, cold, will not affect the ride but will give a slight gas mileage increase. Use a good dial gauge.

 

[70cougar]

2002 DTS - at 75 mph you're turning 2350 - 2400 rpm. I would expect to see 22 - 23 mpg under those conditions. 24+ at 60/65 - 2,000 rpm or so.

That is exactly what mileage I get at those speeds with my 02 DTS.

 

[Ranger]

I agree. 21 sounds just a tad low unless you where fighting a strong head wind or doing a lot of WOT passing.

 

[Takumi86]

is there anything i can do to increase my MPGs?

Don't accelerate quickly maybe? Noboby here has even suggested that yet. One person suggested Wide Open Throttling can cause nore fuel to be used, but WOT means depressing the accelerator all the way, or "flooring it." Even if you don't WOT, if you accelerate quickly it will use up gas very easilybecause you have a v8 engine which makes accelerating quickly very easy ( it's easy to not notice how much power you are using). The Cadillac also automatically switches between 4 and 8 cylinders based on how quickly you are accelerating, so if you accelerate slowly it will only use the 4 cylinders and use less gas.

I came across this page because I also recently aquired a Deville 2002 and was horrified by the gas milage I've been getting, although my mpg was 16. By being careful with the accelerator and keeping my acceleration to only 1mph per second, I have been able to get my mph from a lousy 16 to 18.0 - 18.2.*



*This is not discounting the possibility that the OP's low mpg could have been caused by an engine problem, only pointing out another possible solution.

(I realize I am reviving a old thread, in order to add something that hasn't been mentioned, for people who still own 2002s)

 

[Submariner409]

The last sentences of the first paragraph are grossly in error.

You do not list the model of Deville (2002) that you own. As posted in many, many threads in 2000 - 2004 Seville and Deville (same engines, same transmission, same body weight) The two powertrains have different fuel use norms.

The 275 hp VIN Y cars should get 13 - 18 mpg in city driving, about 17 - 22 suburban/near rural and over 25-26 long haul highway.

The 300 hp VIN cars should get 12 - 17 mpg in city driving, the same 17 - 21 for suburban/near rural and about 24 - 25 open highway.

All on 87 octane gasolines which the engines are calibrated for, the PCM WILL NOT adjust for higher octane fuels, and to date no one - no one - has hacked the FWD 2000 - 2004 FWD Siemens PCM to play with fuel/air ratios outside of those already set.

My 2002 STS consistently gets 17 - 18 mpg (over the 13 years I have owned it) in our semi-rural location; 24.8 mpg long hauls to Florida and back - 1650 miles round trip.

Assuming that TCC is operating correctly. Study up on it.

If maximum fuel mileage is your thing, drive with an egg between your foot and the accelerator pedal. Don't break it.