Fuel economy

From TechWiki
Jump to navigation Jump to search

Fuel Economy

Figures in the table below are approximate, based on real-world experience of SELOC members.

Engine Steady motorway driving Spirited B-road driving on Track
K series (S1) - 118hp 53mpg 34mpg ~20mpg
K series - 118hp 37mpg 34mpg ?
K series - 160hp 44 mpg 30-35 mpg ?
K series - 200hp 34mpg ? ?
Toyota - 190hp 30mpg 20mpg 15mpg
Toyota SC 30 mpg 26 mpg ?
Honda NA 47mpg 31mpg 23-27
Honda SC 36-40 20-25 7-10
Audi 250hp ? 28mpg ?
Audi 300hp ? ? ?

To calculate fuel economy, divide the distance travelled since the tank was full by the number of imperial gallons it takes to fill the car again. 36L = 7.9 Gallons, 1L = 0.22 Gallons (see Google's conversion thingy)

Tank Capacity

While not strictly related to fuel economy, this is a common question on the forums. The 'offical' tank capacity of an elise is 36L, however brimming a completely empty elise can take up to 45L.

Fuel Guage


The fuel guage on an early S1 elise is hopelessly unreliable. On the S1, there is a digital readout which displays: Full>34L>33L>32L...11L>Refill. This can change by as much as 6L on a long corner, but 'Refill' normally means you have about 10-15% capacity remaining (good for about 30 miles of steady driving). Left hand corners and downhill inclines will cause the reading to be lower than actual, right-handers and uphills have the opposite effect. Later S1 fuel gauge tends to be more accurate, on switching to refill, steady driving will see around 50 miles before cutting out.


Early S2 gauge is still a number read out and is better than the S1 gauge as it will give you a good idea how much fuel is in the car, but just displays REFILL at 6lts.

The Later (Cir 04) S2 fuel gauge is a simple 5 segment display which obscures erratic readings simply by having a less granular display.

Fuel economy tips from Guy



Extracted from Guy's well known thread - Bored of your front Speakers? http://arc.seloc.org/viewthread.php?tid=90546&page=1

One of Guy's finest achievements in life is his method on how to become fuel efficient in a Lotus Elise. However the reader will note that Guy's passionate mission to become "Green" has led to several challenges along the way.

So here is Guy's acount of how to be lean and green.

Switching off the engine when going downhill is Guy's commitment to saving energy and helping to prevent climate change.

Guy says, "my favourite gear is neutral. Every chance I get, I run with the engine off and the ignition switch on. I call it driving Soap Box Derby style. I have been doing this for five years. So you can see, coasting downhill has become a hobby".

"I use every downhill slope to coast with the engine off, especially if I can stay above 40 mph—even if I can coast only for a couple hundred feet. Of course, if a green light turns red ahead of me, I immediately turn the engine off and coast. There is no sense in burning fuel, even small amounts if I am going to stop anyway. However, if the battery charge is particularly low and I have uphill slopes ahead of me, I will sometimes use downhill slopes and deceleration to a stoplight to get a little extra charge in the battery".

"Another trick I use is to coast up hills with the engine off if I have enough momentum to crest the hill without going too slow. This turns what would normally be very negative mileage miles into very positive miles. I use the backside of the hills to regain my speed, usually with the engine still off as long as I am not impeding or blocking traffic".

Here is Guy coasting downhill


And to complete his passionate eco mission, Guy decided to recycle a pair of Bobsan's brake discs.

Here is a photograph of Guy cleaning them up ready for assembly.


No Guy you are not supposed to undo that nut.


Here is Guy removing an old brake disc


Eventually after 30,000 miles of coasting downhill, Guy had to fit a new battery.


And his clutch seized up through lack of use


So out came the gearbox.


There, that's better.


Another downside of continually switching the engine off and on for coasting is that the starter motor burns out quickly.


After 100,000 miles of coasting it is time for Guy to do an oil change.


And finally, here is Guy tooled up ready to change a ball joint.