Hypermiling techniques and mpg results

[jdmccright]

The topic of gas mileage is prevalent these days and I'd like to open a thread regarding what techniques people are using to squeeze extra miles out of their tank.

I keep track of my mileage for my commuter '92 Camry. I go abt 70 miles round trip to/from work...50% highway miles, 25% back roads, and 25% city. My baseline was about 26mpg. I rarely use the A/C, then only in the afternoon.

I've started to try a few techniques that those "hypermilers" use to push their cars to the limit and I have to say that there is a difference. I've tried the following:

1) Cruise along in the highest gear possible for as long as possible...that means in O/D and TC locked up...usually at 45 mph and above and light throttle.
2) Shift into neutral and coast down upcoming hills and towards stoplights. I rev the engine up before shifting back into Drive to help minimize slippage and encourage faster TC lock up. I keep my speeds reasonable with the traffic flow...not too fast or too slow.
3) Shut off the engine at longer red lights. I will say that on hills to beware that you'll slowly lose vacuum assist for brakes, so you'll have to press harder to stay put or hold the parking brake.
4) Run the A/C only as long as it takes to cool the cabin down, then turn it off and recirculate the air. The air temp from the registers will stay pretty cool due to the swamp-cooler effect from the condensate that has formed on the evaporator. I use a thermometer to help gauge when it's time to turn it on & off...usually gets uncomfortable above 80 degrees for me.
5) Easy acceleration from red lights and stop signs, especially if there's another one just a block or two away. Why hurry to the next red light?

I do not currently inflate my tires to max sidewall pressure because that promotes uneven tire wear...and rolling resistance is not one of the larger factors. I also noticed an uptick in mileage when I readjusted my timing and cleaned the cap and rotor contacts. As of this writing using these techniques I posted a 30.05 mpg at my last fillup, an improvement of about 15%.

If anyone else has any tidbits they'd like to share, I'm sure we'd all like to hear about it

[somick]

A note to # 2: from what I know when you coasting in gear and not giving gas computer shuts injectors down which means no gas; on other hand when in neutral you still need to keep engine rotating which means some gas spent for this.

I do over inflate my tires. Just a tiny bit. 33 from required 29 pounds. I get 33 on highway. City mileage varies. Depending on conditions from 25 to as much as 30.

A note to #3: shutting down your engine is dangerous! Very dangerous! And pennies that you may save on this do not worth and accident and god forbid somebodies life. Plus this is illegal.

My two cents,

Sam

[Ed_Strong]

'Hypermiling' Is Dangerous, Says AAA
Extreme fuel-saving measures can put motorists at risk

read it here ==> http://consumeraffairs.com/news04/20...prices274.html

[jdmccright]

I'll agree that some of the techniques are dangerous and those are ones I do not engage in...coasting with the engine off and drafting to name a few.

Regarding #2, the ECU will feed gas if your foot is off the accelerator whether you're in our out of gear.. in both cases the engine is at idle state. But in gear, the engine is providing braking through the torque converter, so idle fuel rate is being consumed at 2000 rpms versus 750 rpms. In a manual transmission, the effect is the same only more pronounced since there is a direct connection between engine and transmission...no slipping torque converter.

Regarding #3, I find it difficult to see how my vehicle, stopped at a light and engine off, surrounded by other stopped vehicles, could cause a fatal accident. I will reiterate that I have only done so AFTER I have come to a stop. And according to my state's motor vehicle laws, it is not illegal to do so...yours may be different.

Perhaps "hypermiling" wasn't a great word to use for this topic given it's negative connotation, but will hopefully generate good, safe, and economical driving habits.

[somick]

Originally Posted by jdmccright

Regarding #3, I find it difficult to see how my vehicle, stopped at a light and engine off, surrounded by other stopped vehicles, could cause a fatal accident. I will reiterate that I have only done so AFTER I have come to a stop. And according to my state's motor vehicle laws, it is not illegal to do so...yours may be different.

Iam sorry. I misread your statement. I was referring to coasting with engine off.

Shutting down your engine at a traffic light will probably save you some gas. When I lived in San Jose I specifically timed some traffic lights. Sometimes up to 5 minutes of red. But I still doubt that new/rebuilt starter is worth it.

Regards,

Sam

[somick]

Originally Posted by jdmccright

Regarding #2, the ECU will feed gas if your foot is off the accelerator whether you're in our out of gear.. in both cases the engine is at idle state. But in gear, the engine is providing braking through the torque converter, so idle fuel rate is being consumed at 2000 rpms versus 750 rpms. In a manual transmission, the effect is the same only more pronounced since there is a direct connection between engine and transmission...no slipping torque converter.

I keep thinking about this statement but unfortunately cannot find any information neither for nor against it. From what I have read at different automotive forums "when your foot is off the accelerator injectors do not get any gas"

Hopefully somebody else will chime in...

Sam

[Brian R.]

Most Toyotas will stop injecting gas when your foot is off the accelerator and the rpms are above some specified rpm. This is called the fuel return speed or fuel return rpm.

The fuel return rpm is 1500 rpm in the 5S-FE and some 5VZ-FE ('00 4-Runner), and 1200 rpm in the 1MZ-FE, 3VZ-FE and 5VZ-FE ('03 Tacoma). With a manual transmission, the 5VZ-FE has a fuel return rpm of 1000. You get idle injection below that rpm in these engines. For example, see pages SF-66 and SF-75 of the '99 Camry manual or SF-65 of the '03 Tacoma manual.