FatherTo1

Why are these two values different? Is the average MPG (on the bottom) the all-time average? If so, both metrics are woefully off from my calculated values.

I am noticing that the After Refueling average is optimistic by as much as 1.2 MPG in our 2013 LS 460 whereas the algorithm in our 2006 LS 430 was spot on, no matter the amount of coasting. The 430 estimate often matched my calculated values exactly and was never off by more than .2 MPG.

mckellyb

I've found every single vehicle I have owned has at least a 5% error, inevitably on the high side.

Some have had 15%, i.e. useless.

Being as it's a super simple (relatively) calculation...fuel injector open time at pressure 'x' and distance traveled.

The speedo/odo is freakin' spot-on, so I have no idea why it's significantly different. I'd like to think it's not intentional, but I've seen this in many a car, and it bugs me to no end.

BTW, 'coasting', foot off the throttle, in gear, is a good thing when engine RPM stay above about 1,500. The injectors shut off 100%, so you're not burning any gasoline. If you watch the tach, you can see where the engine essentially starts running under gasoline power, again. The tach will jump a teeny bit or just a little bump then steady at whatever RPM is called for to keep the engine alive. That RPM is your, pardon the pun, break point where forward motion goes from free to you're burning gasoline.

Doublebase

So what you're saying is when coasting in gear keep the rpm's above 1,500? I coast a lot and I always keep my dash set on that meter that tells you what mileage you're getting at that point in time - I find that the lower the rpm's when coasting, the higher the fuel mileage I get. This car loves to coast, I almost never touch the gas pedal when going down a hill...the thing will roll forever, fast too.

But these cars have injector shutoff? Didn't realize that. How does the engine spin above 1,500 rpm's with the injectors shut off 100%? Engagement with the torque converter?

Gbp

If 2013+ works the same way as prior years, the average MPG represents the average since the reset button was last pressed while displaying that value. Pressing reset changes the value to zero. In a similar way, one can selectively reset the average speed and the time elapsed.

roadfrog

LOL. You guys have too much time on your hands! Whether I get 20 mpg or 22, makes almost no difference to my gas budget.

mckellyb

Yep. That's it right there, but it's all about a locked converter. Might be 1,800 RPM, or 1,675, though I had a Mercedes which was about 1,200 (surprisingly low, but the converter on that car was "tight" enough MB didn't need a lockup mechanism). See, this couldn't be done with carburetors because there's no way to shut the fuel off. However, with electronic FI, unlike mechanical FI, the ECU just kills the signal to the injectors. When it needs fuel to not stumble, the ECU fires 'em back up.

Tonight, on my way home from work, I'll play around with it and see where the ECU turns the injectors back on. Imma gun predict...mmmmm...1,500 even.

Honestly, I never thought to look. I'm so happy with double-digits starting with a '2' on my daily commute, I just never thought about it.

Funny how a car two years newer to market, 500 lbs. heavier, same displacement but 60 more HP, manages about 10% better MPG than my '05 STS (the RWD one). Oh, and it's quicker to 60 MPH, too.

Doublebase

Thanks, I'll have to pay attention to where my tach is when I'm getting my best mileage. I've been able to do some amazing things with this car - gas mileage wise - I average 26.5 mpg a week...I even get better gas mileage than my wife does in her Honda CRV. You can't really beat that with a V8. This transmission does wonders for fuel economy, every car should have it.

roadfrog

The new LS will have a 10 speed. Unbelievable.

mckellyb

I almost don't believe it, but I checked half a dozen times last night...1,500 RPM on the nose. Tried this in different gears, too, because it's impossible to 'see' happen in 8th.

Tried it in 6-2, right at 1,500 every time.

Even having 8 speeds gives me goosebumps when I think about rebuild time.

teedub21

2018 Mustang GT will also feature a 10 speed auto. Way of the future I guess. I remember when a 5 speed in a stick shift was a "new thing".

roadfrog

Remember when the Corvette cam out with a 6 speed manual? Shook the automotive industry to the core. Lexus was the first to introduce the 8 speed auto when they released the LS460 in 2007. Although not the first to release the 10 spd, it was close. Ford and GM teamed up to produce and design the new 10 speed in their trucks.

Doublebase

Haha, I had that Corvette with the 6 speed (actually got great fuel economy with it when my foot wasn't buried in it).

Isn't the 8 speed LS transmission used in the Cadillac now? Thought I heard that...probably the best thing on that car.