Read this:
http://autos.yahoo.com/news/6-drivin...is-summer.html
especially the section on acceleration.

 

Absolutely excellent information. Thank you.

For those who have a hard time evaluating the graph, the top yellow and white lines are the data for the speed vs. time (acceleration, so the steeper the curve is, the harder the acceleration is), and the bottom two, solid yellow and while curves are the data for the miles per gallon, using the same scale on the left.

Internal Combustion engines that have no turbo or supercharger are known to be more efficient at higher RPM, however, although the engine is more efficient, (power delived per amount of fuel delivered) higher rpms also mean more fuel consumption, which we don't need. But this is a tradeoff, thus I wonder if the principle makes such a big difference, specially since accelerating twice as fast wont rev up the engine significantly more - Mitght this be where this increase in mpgs come from?

I always wondered about the effectiveness of slowly accelerating to a certain speed vs. accelerating more moderately, but without a simple way of making realiable measurements, this is complicated. These guys did it, and the results indicate that in fact accelerating moderately rather than very slowly is more efficient. - I'll try to hunt down the study that this came from and see how reliable it is, and let you all know. Great input. Thank you!

 

I replaced the filter right after buying GX, and I did not think about doing the comparison.

 

I'm getting the same thing maybe a little less. The funny thing is when I first got it at 40k miles I was getting 16 mpg from my usual driving all the way til about 110k miles. I let my brother use it for about 20k miles (but only about 3 months() when I got it back I got 14.1, 14.2 14.1 mpg when I didn't need a/c then 13.1, 13.3, when I used a/c (hand calculated) My on board says 16 mpg. I used to get a little over 300 miles to the tank easily. Now the light comes on at about 250-260.

There's a few things I'm going do and report back to see if there are any improvements

1. Check brakes/calipers
2. change air filter
3. change all the drivetrain fluids.
4. change the spark plugs.

 

Ugh, now I find this out.. I've been using the K&N filter for about a year now. So when the mass air sensor gets dirty.. how do you clean it? Is it a user serviceable part?

Turby

 

There are a few different variations used by each manufacturer. They are serviceable. The cleaner is a spray either electrical contact cleaner, or non chlorinated brake cleaned. The sensor is part of the air cleaner system. It is delicate, so be careful.

 

[QUOTE=sphy1005;6465616]I'm getting the same thing maybe a little less. The funny thing is when I first got it at 40k miles I was getting 16 mpg from my usual driving all the way til about 110k miles. I let my brother use it for about 20k miles (but only about 3 months() when I got it back I got 14.1, 14.2 14.1 mpg when I didn't need a/c then 13.1, 13.3, when I used a/c (hand calculated) My on board says 16 mpg. I used to get a little over 300 miles to the tank easily. Now the light comes on at about 250-260.

There's a few things I'm going do and report back to see if there are any improvements/QUOTE]

Another factor in MPG numbers may have to do with the fuel - all of the cars in my family get about 2 MPG less now than 4 or 5 years ago. For my Cummins pickup it was the switch from Low Sulpher to Ultra Low Sulper diesel (to meet newer emission req'ts). For my GX & Corolla the gas here (Salt Lake City area) is now typically 10% ethanol, and something they call 'oxygenated' gas in the winter - both things I have read contribute to lower MPG. So it looks like it's part of the bill we pay for cleaner air - just another factor to complicate all the other factors that contribute to overall MPG.

I record each & every fill up and so have good, long term data for each car, and adjust tire pressures every 2 or 3 weeks, keep new air filters installed, etc, so IMO the 'cleaner' fuels account for at least some of the loss in MPG over the last few years.

 

I will add that when I went back to the recommended higher octane, my milage improved. The difference increased cost for 93 vs increased milage was a wash.

 

Intresting. I did not know that the ethanol could contribute to less MPG. I do check my tire pressure all the time at home and keep it at 36psi. Oil change every 5k with mobil1 syn and air filter changed every 10k. My brakes have started to vibrate (again) so i'm gonna order new rotors sometime next month and check the calipers. Probably the drivetrain fluids then too..

93 octane all the time.

 

"I did not know that the ethanol could contribute to less MPG. "

Yep, my MPG has been going up for the last couple of months. No more winter gas.

 

Thanks - I pinged another friend who is car knowledgeable and he says that sometimes the sensor is located right after the filter. I'll do some research to see if I can find out the exact sensor location. How delicate is it? Any more delicate than a dSLR sensor?

Turby

 

It is between the filter element and the engine, just need to take pipes off and you will fet to it. If it is the one with the very thin wires which are the sensors, they are delicate

 

OA,

Ethanol, fuel additives, aftermkt air filters, turbonators... yada yada yada.

Suppose you are able to get to 16.1? So what, that's only a 14% improvement and probably STILL will be killing your budget.

Using your numbers as an example, let's say you drive a lot and put on 2,058 miles per month (~ 25k miles per year):

2,058 miles / 14.1 mpg = 146 gallons (roughly 6 full tanks)
146 gal x $4/gal = $584 / month in gas

Now let's say you can get to 16.5mpg...
2,058 miles / 16.5mpg = 124.7 gallons
125 gals x $4/gal = $500 / month

Net Savings = $84 per month = $1,008 annually = $19.38 per week

Now, lets suppose you were able to get to 20mpg...
2,058 miles / 20.0mpg = 102.9 gallons
103 gals x $4/gal = $412 / month

Net Savings = $172 per month = $2,064 annually = $39.69 per week

No doubt I'd love to save $1-2k per month but I need the GX so it is what it is. In all sincerity, 14.1MPG city is not bad at all - not great for FL where it's generally much flatter compared to the mid-atlantic - but all in all it's not bad.

Bottom line, and please don't take offense, it sounds like you are plainly in the wrong vehicle for your budget. The RX or a Lexus sedan much be a more prudent choice.

Good luck

 

Few other things to consider:

-ethanol not only reduces your MPG, but can cause considerable damage to your engine (especially if it was not designed for it). Case in point, many 2-stroke lawn equipment motors are either becoming damaged or degrade in performance because of the newly introduced ethanol. Vendors are actually encouraging owners to use higher octane fuel because of this...thankfully the ethanol credits will expire and hopefully push us back to unadulterated fuel!

-check the types of tires you are running. Different tire types make a huge difference in both quality and fuel savings. I went from the Dunflops to Michellins, and my MPG went up by almost 2 in the city (without changing driving patterns.)

-remember this is a full-time 4wd vehicle...there is no way around this

-check your maintenance logs...an improperly tuned engine will give poor performance.

GL

 

See... inputs like this is why I like this forum so much. I had not thought about the actual tire type. I keep them super inflated, but had never thought about that. I'll keep that in mind, however, did you have the car aligned when you changed to the Michellins?

My GX is tuned and well maintained.