I have a non-hybrid standard MX-6 (Gen2, 4cyl). I'm starting to try to optimize my mileage and wanted some suggestions. Most of my commute is on back roads so I often have no one tailing me. What I'm wondering is how to accelerate and what gear to cruise in. I read that an ICE is more efficent at faster accelerations, but my common sense tells me that high RPMs burn more fuel than low RPMs.

Does driving at too low of an RPM waist fuel?
Is slow gradual exceleration less FE than more aggressive acceleration?
Should I shift early or late?
Suggestions on what RPM to shift at, and what RPM to cruise at.

Here's my checklist as it appears today.
1) Drive in highest gear possible.
2) Keep tire pressure, oil, filters well maintaned.
3) Drive slow.
4) Minimize A/C
5) Coast whenever possible.
6) No Jackrabbit starts.
7) Always maintain momentum when possible.

 

What year MX-6? is it OBD-2? Stick or auto?
Yeah, I have a bunch of questions, but I'm trying to understand your driving situation.

Sounds like you have all the basics covered with your checklist.
This is all old news, been said before.
To go a little further in detail:

1) Drive in the highest gear possible, without lugging the engine. A vacuum gauge would be handy.
2) Pump up your tires to the maximum recommended pressure that is on the sidewall. Higher pressures will give you fuel savings, but at the expense of a harder ride.
Every tire has a maximum cold pressure rating imprinted on the side of the tire.
You can go as high as that rating while the tire is cold but do not exceed that maximum rating.
3) Drive as slow as your schedule allows without causing an unsafe condition on the highway, but still keeping the car in the most efficient speed range. My Insight will get maximum fuel economy somewhere between 39-44 mph. Go any slower and the engine won't pull 5th gear. Go faster and aerodynamics start killing fuel mileage. Some people that work night shift have the luxury of empty roads, they get to drive as they please.
4) Air Conditioning: Minimize it or just don't use it at all. Just be sure to use it every so often to keep the oil circulated in the system and keep the seals happy. Try using A/C only when coasting to a stop, use the deceleration to power the compressor instead of fuel.
5) If it's a stick shift, and you are comfortable with the technique, try coasting with the engine off (may be illegal in some states). Just be aware of the safety aspects (no power brakes or steering), it is somewhat extreme. You wouldn't want to use this too often, because of wear on the starter during numerous re-starts.
6) Accelerate slowly but gradually.
7) Don't give up momentum once gained. Drive like your brakes don't work. Take turns as fast as you can safely. Anticipate traffic signals, 1 or 2 signals ahead. Look for gaps in traffic that will allow you to maintain your set speed.
Drive with the load, not to maintain a set speed. Be willing to let your speed drop a little on inclines.
8) Drafting - whatever you are comfortable with. I personally don't like to draft behind large trucks, for safety reasons and to avoid paint dings. But a slight back and next lane over draft can boost the mpg's and is much safer.

Having a real time instantanous miles per gallon display really helps. If your car is OBD-2 compliant ('96 or newer) an aftermarket device is available that will provide this info (and more). See: http://www.scangauge.com/
I put one in my wife's Acura TL, she likes to see how she's doing with her gas mileage.

Hope this helps.

Regards,

 

Yes... It's a 96 ODBII compliant and the scanguage is in the mail. That should help me refine my technique.

I think I know what you mean on the RPMs. Too low and you feel the car strugle, a bit higher and your fine, just not as responsive, too high and the car engine-brakes when you let off the gas. I try to keep it in the range where it doesn't strugle or buck to accellerate and doesn't engine-brake.

For the Mazda, this translates to about 1500-2000 RPM. If there are any MX-6 or Ford Probe owners that could corroberate, I'd appriciate your input.

 

Great advice over all Hawk! The Scan tool should help a lot for any car that lacks MPG displays. As far as coasting ICE off goes I agree that it should not be done very often on a non-hybrid. To further elaborate it should only be done:

1) If you are fully aware of the safety risks. (I know you already said this but you can't be too careful)
2) In light or no traffic.
3) On a downhill where you can coast for at least 1/3 of a mile.

Also if time and traffic allow you should try to "drive with the load". This means you lose speed going up hill trading kinetic energy for potential energy and gain speed going downhill trading the stored potential energy for kinetic energy. You should crest hills going as slow as you can while still in top gear, time and traffic permitting of course.

 

With a manual transmission, when you accelerate, try to accelerate at around 75% throttle (any less and the engine runs less efficiently due to suction losses, any greater and the engine runs at richer fuel:air mixtures). Shift early, ideally keeping RPM's below 2000. The lower the RPM (without lugging the engine) you can cruise at the better, since friction losses in the engine increase with RPM. I shut off the engine on downhill coasts quite often in my non-hybrid car. My car doesn't have power steering and the power brakes provide 3 pumps of the brake before losing the power assist. I don't use the starter to restart the engine. To restart, I make sure the ignition is on, put the car into gear and release the clutch to restart the engine.

 

Hi All:

___HawkGT647, great post for the non-hybrid driver!

___Dan, I would also consider some 0W or 5W-20 in your Mazda’s setup list as well …

___Basjoos, neither the Ranger w/ a stick or the Accord ever see > 2,000 RPM during ANY acceleration except when south of the speed limits at highway cruise or when absolutely necessary. That necessary is a very rare occurrence. I do not have an FCD in the Ranger unfortunately but I do short shift her at 1,200 - 1,500 and the FE speaks for itself. She has the latest gen 2.3 L w/ 150/150 HP/Ft-Lb’s (the Focus ICE minus balance shafts for higher peak) so there is a good deal of torque down low vs. the previous gen I4’s. That could make a large real world difference in acceleration technique for Dan?

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net