Intellidelphian

I have an 04 TL and I'll be taking a long trip soon. I was wondering if anyone knew at what speed is opitumum fuel economy maintained.

Spiritman

54.35422 MPH or right around there. Doing this on my 06TL I was able to maintain 39 MPG for about 60 miles......

subinf

Between 55-60, had a flat tire and the spare was on. Best gas mileage I've ever seen with the TL.

BLACKURA_NY

iTrader: (6)

yea 55MPH just a shade unde 2 RPM ...with all my mods... i was soaring at 35MPG on flat surface

on a downhill, ive done like 37/38 MPG

sixsixfour

55 for me. even on the Evo.

jazznut

I concur with everybody, did 55 mph and I was at 34 mpg.

MichaelBenz

iTrader: (2)

Flat out floored. Then its like...so much fun....who cares!

rimz

like everyone else said, you get the most speed with the lowest fuel consumption at 55mph...

i haven't tracked my MPG doing this, but i do 55mph at 1500rpm...imagine doing that straight on a full tank...your MPG would soar...

law of 5's: 55mph at 1500rpm in 5th gear...

6spMike

Probably the slowest you can go in top gear without lugging the engine, around 45 for 6mt, 50 for 5at.
I couldn't stand that for long, though...

lusid

O god, that would is too slow...

fish008

READ THIS, TRUST ME IT WILL BE WORTH IT AT THE END - Driving back from Florida to Michigan after buying my TL I got 29 or 30 on all tanks averaging around 78, but on one tank I got over 31 with an average speed around 74. I know that those are not even close to the guy who got 39 but how much is your time worth. If you were on a 1000 mile drive and averaged 55 mph it would take about 18 hours 10 minutes on the road to complete that trip. BUT if you averaged 75 mph over that same trip you would complete the drive in only 13 hours and 20 minutes; for a difference in travel time of about 5 hours. If on that trip you average 39 mpg you would use just less and 26 gallons of gas, if you got only 30 mpg on that trip you would use just less that 34 gallons. SO, at $3 per gallon getting 39 mpg would cost you about $78, while getting 30 mpg about cost you about $102, $24 dollars difference. Remembering the difference in time of 5 hours putting the value of your time at about $4.80 per hour, and that is if it is just you. If there are 2 people in the car it is half of that, $2.40 per person, per hour, and 3.... I don't know about you but my time is worth WAY more that $5 an hour. I thought about writing a book on that once, not that this post isn't one, but it would have been titled "How Speeding Can Pay."

Desert_TL

from tucson to san diego i averaged 90MPH and got 26MPG

on the way back, i averaged 75MPH and got 37MPG

Black_05_TL_6SP

I am telling you, it is a government conspiracy!! It was determined back in the 60's that 55 was the optimal speed for fuel economy!! That was why all the highway speed limits where 55mph. To help in the effort to conserve energy. The thing is, cars are still all geared for that to be the optimal efficiency.

It falls in with the 0-62 mph thing. Almost all cars will go from 0-62 without having to shift from 2nd to 3rd. This is so the manufactures can produce the best 0-60 times from each car. This too has been around for quite some time.

Non the less, 55 is optimal fuel economy range. I personally hate going that slow if the speed limits are 70. Good luck with the trip.

6spMike

There's nothing magical about 55 mph.
Aerodynamic (wind) drag increases with the cube of the speed. Doubling the speed of travel requires 8x more power.
So the highest mileage will occur as slow as the car will go in the highest gear, with the caveat of not lugging the engine.

All of those college mpg challenge cars that get 1000 mpg and stuff do it below 5-10 mph.

My guess is the 60's decision was probably also based on safety and time to travel, not just fuel economy.

subinf

Although I did get in the 30's averaging well above 80 miles an hour a few times last year

SouthernBoy

Speeds weren't changed to 55 in the 60's. That happened after the first oil embargo in '74.

Best mileage I have ever gotten on a trip with my '04 manual TL was in September '05. Started out at noon. Outside temp was 86 degrees. Used the A/C the entire way and was on vacation, so the car was loaded with luggage and the wife and I. Roads and speeds went from an average of 62 MPH to 76+ MPH. First leg of the trip (around 260 miles) netted 33.94 MPG. Not too shabby.

groovyone789

Actually, I just learned that many places changed the speeds to 55 in the WWI-WWII era. In that time they were not only concerned with saving/rationing gas but they were concerned about rubber too. They lowered the speed limits so tires weren't used up as much. In fact, at that time they hardly sold any tires, the rubber was saved for war vehicles. In that era lots of rubber came from the regions that we were actually fighting making it really hard to supply the country with rubber. Same deal with gas, save some for the military and decrease dependence on foreign countries.

They probably did change them in the 70's too... just that trend started back in the 20's-30's.

groovyone789

Actually, I just learned that many places changed the speeds to 55 in the WWI-WWII era. In that time they were not only concerned with saving/rationing gas but they were concerned about rubber too. They lowered the speed limits so tires weren't used up as much. In fact, at that time they hardly sold any tires, the rubber was saved for war vehicles. In that era lots of rubber came from the regions that we were actually fighting making it really hard to supply the country with rubber. Same deal with gas, save some for the military and decrease dependence on foreign countries.

They probably did change them in the 70's too... just that trend started back in the 20's-30's.

Back to the point, 55-area is really where I've had the best mileage. Highest I've ever seen on my car so far on a tank was 25mpg at purely highway driving.

6spMike

For a whole tank/trip? Really? That ain't so good. It should be better than 30 if you are going 55.

groovyone789

no it was about a 170 mile trip. and i wanted to fill up while i was still in wisconsin (cheaper there). The car was brand new then and still not broken in. It's a TL-S. And i just noticed that I got the best mileage (watching the computer) when i was in traffic and going about 55. When the road was clear I would be going like 70-75. So I guess it averaged to be about 25mpg.

Kostyan

mt equipped should get the best mileage. There's that magic 6th gear...need to keep the rpms between 1800 and 2200...drop rpms to 1500 in 6th and your engine will strain...someone before on here suggested 5th gear as most economical, I disagree with that.

Repecat

Just to set the record straight, during WW II, the speed limit, at least in Massachusetts, was 35 mph. After the war, each state set its own limits until the 1970s, when the 55 mph limit was nationally mandated because of fuel shortages.

6spMike

1500 in 6th is about 45 mph.
The 5ats actually have a higher top gear; 1500 rpm in 5th is 53 gearing-wise, but a little slower due to the torque converter.
I'll bet in actuality they are exactly the same.

SouthernBoy

I was speaking along the lines of "modern day" alterations to the national speed limits. You may have a good point specifically with WWII.

The U.S. held title to the largest and nearly the only rubber producing areas in the world before WWII. The Japanese desparately wanted control of this production as well and continued steel and oil shipments from America. We tightened the noose on the Japs, forcing theirs and Germany's hand because Roosevelt desparately wanted into WWII.

He got his wish and the rest is history as they say.

kenny5

On a 110 mile trip, my average speed was 65 and my mpg was only 27, but that was with 2 passengers and under pouring rain. I guess rain added resistance and passengers added weight, causing mpg to suffer. My best mpg so far was 33 at 55 mph, which was obtained during break-in period. In city traffic, I average 18.

gt1

This is a well known fact that the best fuel economy is obtained by driving at the lowest sustainable speed in the highest gear.
Someone always asks this question when fuel prices go up.

Formula 350

I got the performance tires and you can tell... the car slows down faster when you are in neutral due to the friction..

My best tank is about 30... if I really drive like granny, I have seen it as high as 34 with all highway for about 60 miles... at 60 mph... got the 6 speed...

My normal 'freeway' driving is 28 or 29... my average for the car is 24 and rising a bit toward 25...

3rdGenHybrid

i never really thought about it....i heard cali's up at over $4 a gallon...ill think about best mpg when it gets that high on the east coast....

SouthernBoy

Last spring when I had Michelin Pilot Sport A/S tires put on my '04 manual TL, my city mileage dropped around 1.5 MPG and my highway around 2 MPG. I noticed the difference as soon as I mounted the wheels with these new tires back on my car. With the Stock EL42's my car would coast backwards out of my garage. With the new Pilot Sports, the car stayed put where it was. I would say that's evidence of a fair amount of rolling resistance.

NBP07type_s10

Not to sound cynical, but if you purchased an expensive car and are spending the money to put premium gasoline in the car (as instructed in the owner's manual), you should be able to afford the extra money to drive well above 55 and save some time.

If I wanted to drive at 55 and get superior gas mileage, I would have bought a Toyota Camry or Honda Accord, not a TL.

I agree with Fish008, it is worth the time saved. Plus driving at 55 when the speed limit is 65 or 70 is hazardous since traffic is flowing at alot higher rate of speed around you.

SouthernBoy

There's an old adage in boating.

"If you are concerned about fuel consumption, you probably should not be considering that boat."

The same could be applied to cars. While I certainly like the fact that an engine will deliver decent and acceptable (surprising) fuel economy, that is not my primary concern, nor a deciding factor in my purchase. I consider good fuel economy to be icing on the cake of a car that satisfies all of my other requirements first.

Also your comments about those who buy a car which requires premium fuel, then question whether or not they want to feed it 87 or 89 octane never ceases to amaze me. It's not like automotive manufacturers hide this information until after the purchase and then the buyer finds it buried deep in their owner's manual in ultra-small print.

I think getting 25 MPG in the city and 34 MPG on the road from a TL is darned good mileage and I'm quite pleased with it.

sandiegodrive

720 Mile road trip from San Diego to NorCal got 33 MPG AVG at 78 MPH

Trunk and back seats were fully loaded with stuff.

MisterFubar

iTrader: (1)

I averaged 35.4 doing 75-78 in my 04 5AT, thought it was a fluke but I got 35.2 on the same drive going the opposite way(coming home). I filled it up, got right on the highway and stopped once for food, and once for the bathroom, 470 miles one way and my low light came on a few miles before I got to where I was going. Myself, 1 passenger, 2 sets of golf clubs, a weeks worth of luggage and a couple hundred pounds of test equipment.

Car has 60k on the odo, and is basically stock with the exception of a AEM, throttle body coolant bypass, and relocated IAT. Also have the tires aired up to 40 psi when I'm going on long trips on roads that I know are fairly smooth.

Doing 50-60 I normally average about 38.

I'll be doing a 3500+ mile road trip next month, my goal is to get 500 miles on atleast one of the tanks.

I didn't buy the car to get good mileage, but it's fun to see what I can milk out of it when I'm on the highway.

Intellidelphian

It's not about whether you can afford it or not its about being smart with your money. I'm not interested in blowing money on gas when its not absolutely necessary. If I can save a couple bucks driving at 68 as opposed to 80, then as long as I'm in no rush, I'm going to drive 68.

fish008

I think it would be interesting to see what people REALLY averaged on the longer trips where they say they averaged 90 and then got mid to low 30s. It is easy to maintain 90-100mph for a couple of minutes but you are going to get caught up and your average speed will suffer big time. The highest I have ever averaged for a couple hundred miles (according to the car which I believe to be accurate because it is a mathematical formula the car calculates (miles traveled/time)) is 78mph over maybe 120 miles or so. An average of 90 seems...difficult.

subinf

^ from Oregon to SF (600 miles) I averaged 85 miles an hour and was getting 29 mpg. I'll take a picture of the MID next time I make the trip (probably in May)

screaminz28

iTrader: (1)

You guys have some lead feet to AVERAGE over 70+ mph. I just went 450+ miles one way, mostly 70mph limit highways, a little sluggish through ATL, and by cruising around 75 most of the time, I had a computer derived average speed of 67 mph, and got 34mpg, 05 M6. To AVERAGE 90 mph, you'd have to be riding at 90mph for a set amount of time, and be calculating JUST the 90mph travel time, OR be hauling some major butt for the majority of the trip. I think we have two different types of people calculating. Someone like myself - I reset the trip computer right after I fill up with gas and leave for my destination and look at it when I get to it, and the other, where they get on the interstate, set the cruise at 90, and then look at the mpg. It's a LOT easier and more efficient to MAINTAIN a speed than it is to get up to it.

subinf

I point my car south and go...I don't like speed fluctuation when I drive and I only stop for gas. That is about as consistent as you can get.

Eoanou

Not to hyjack the thread, but what are the gas prices for where you guys are?

Here in CT it's roughly 3.15$ for 93 Octane.

Intellidelphian

I'm live in the Philadelphia Area ($3.00), but I fill up outside my job in south jersey where the Premium grade is $2.80