Yamae

LOL.　Read the post #4. Some people tend to just react and notice what happens next.

LScowboyLS

I don't have exact figures, but I did an informal test at 40 mph on a long level road that went on with no stops for about 30 miles and calculated that my mpg was well above 30, never gotten anything like that at 60 mph

I understand what you mean, that the engine is operating at it's most efficient rpm as far as fuel burned per unit of power, and that this would be best fuel efficiency on a dynamometer, but even though the LS400's coefficient of drag is a respectable 0.29, because the velocity is squared, it still seems that best mileage is going to be near 40 mph


this assumes you are doing nothing but driving, when I am driving, I am talking on the telephone doing business or listening to an informative and hilarious radio show called Car Talk - so no time is being wasted!

dengman

who wants to throw down on putting a ls400 in a wind tunnel.

sam12345

iTrader: (1)

yeah but in the real world there are hills and with a 5 speed it will shift down every time you go over an over pass ect... At 55 to 60 it will not. But maybe 50 but no less.

ls400geek

My computer said I was getting 30.0 mpg on the way down, but after actually measuring it at the pump it came to 27.25mpg. It seems like the computer always reports better gas mileage than the car gets. Question: is the Japanese "gallon" the same as the American "gallon". I am guessing you actually sell gas there by the liter?

PureDrifter

iTrader: (10)

make sure you use the "tank" mpg, not the current or "other" one, which is user resettable.

even then the tank mpg is only really accurate when you start from a fully filled car.

timmy0tool

iTrader: (7)

dang Yamae always with the knowledge!!!

ls400geek

Yeah I used the tank one only, from a full tank, and it always reports better MPG than it really gets by 1 1/2 to 3 mpg.

Yamae

We don't use "Gallon" at all. It is against the regulation to use it here. "Gallon" is now only used in US. UK "Gallon" which differs 20%+ is not officially used in UK any more.

My kids were so used to those good old American standards that they were having a hard time after coming back to Japan to get used to the "Metric". I feel sorry that many people in US still need to use those non world standards.

islagiatt

I just bought my first Lexus and wondered about optimal speed for maximum gas mileage. According to estimates at http://www.automobile-catalog.com/ec...us_ls_400.html, "Estimated mileage (fuel economy) by constant speeds on top gear [5th], steady ride without acceleration or braking, flat concrete or tarmac surface, no wind..." are:

• 28.1 mpg @ 44 mph (70 km/h)
• 27.8 mpg @ 50 mph (80 km/h)
• 27.4 mpg @ 56 mph (90 km/h)
• 26.6 mpg @ 62 mph (100 km/h)
• 24.5 mpg @ 75 mph (120 km/h)

This information indicates that the optimum speed for maximum fuel economy might be around 45 mph. In any case, 65 mph on the freeway should (in theory) produce better gas mileage than 75 mph (which would only save the driver about six minutes over 50 miles and 12 minutes over 100 miles). However, driving 75 mph instead of 65 mph over 500 miles would save the driver about an hour. While I certainly enjoy driving fast, speeding likely decreases fuel economy while increasing risks of accidents and tickets. I wonder if the time saved over shorter distances is worth the potential costs.

Sc0pe

iTrader: (1)

I can confirm getting nice MPGs in the low 40s. I generally use that speed around town roads, and then get up to 60 on main roads. I'm kind of curious if lowering provides any significant gas mileage increase.

RA40

iTrader: (6)

The car still has the same frontal area and what more-less flows under will not be significant in real world. A wind tunnel might show some differences.

Doc Yota

The mileage variation between LS's I have been monitoring for about ten years between 3 different LS models. My old 98LS had the best at 29.8 on the highway with a/c running and WOT from time to time when passing. My 99 is second best at 26.5 but with 20 inch wheels I get as low as 24ish. My 02 LS430 worst at 23.8. All cars have K&N drop in filters(the air box hack on my 99 only) and synthetic oil in all. I just can't figure out why the 98 has always been the best of the bunch when it comes to MPG.