Engine Load/Ultragauge

[Andrew Gibbens]

I think you have to treat the instantaneous mpg figure with caution, whether from a dash readout or an OBD device. Drivers will concentrate on getting a 'good' number from the readout which may not be good for economy.

For example, very slow acceleration that gives the highest mpg figure is, despite everyone's gut feeling, not the most economical way to accelerate. Best practice is to use wide-open throttle at medium revs (around peak torque) as then the engine is then working at maximum efficiency. It's like removing a band-aid - a short sharp pull hurts less than a long slow reticent one. If you want confirmation, look at economy competitions where 'coast and burn' techniques (maximum acceleration followed by coasting with engine off) give the best results - not a good idea for road driving!

Similarly the best mpg reading is obtained when doing the single most uneconomical thing in driving - using the brakes.

[honda03842]

Andrew,

I don't understand how using the brakes gives the best mpg. Best mpg for me is rolling, to the stop sign or down hill in neutral, particularly asy with a manual transmission. I like see instantaneous mpg but focus on engine load. Maximizing energy to me is reduce percentage of engine load. As you suggest keeping the engine in its most efficient range is important. For us it seems to be between 3000 and 3500 RPM.

I really should take a look at the engine power curve.

[DMAC1]

When trying to get the best fuel mileage, steady smooth driving with moderate throttle is ushually where you will get the best result, most fuel injected vehicles when the control module sees " wide open throttle" pretty much poors as much fuel into the engine as it can get, generally resulting in aproximatly 5 ish to 1 fuel mixture, the peek ration is 14 ish to 1.