Mileage test’s
 

Mileage test’s

A good reason for not speeding !
Forget speed cameras, forget getting pulled by the police.
Your pocket is what you should be worried about.

Now a while ago I asked some questions related to MPG and I got some different answers.

Anyway I thought I’d put it to the test in as scientific way as possible.

My test followed the following conditions:

1> Vehicle, Vaux Astra 1.4 Estate.
2> Engine in good condition.
3> Traffic: 90% Motorway and some mild traffic
4> Weight: Unladed, only driver
5> Tyres: checked before tests in 3 pressures
i> NORMAL (29 front 26 rear)
ii> PLUS (30 front 36 rear)
iii> MAXIMUM (30 front 43 rear)

6> Fuel: 44 litres, measured by, allowing the tank to hit the red light then brimming to 44 litres, then running till tank hits red light

7> Speeds:
i> ANY = initial test, any speed, flooring it when I could, no upper speed liomit
ii> SPEED LIMIT = keeping to the speed limit of the relevant road.
iii> 3000RPM= not allowing the car to rev higher than 3k rpms
iv> ANY (not)= as ANY but not exceeding 70mph
v> +10mph = no higher than 10 MPH higher than the speed limit of the given road.

8> Days: how many days my full tank lasted (driving days!)

OK so download my spreadsheet to see the figures.

http://www.playback.demon.co.uk/petrol.xls

The list is sorted by best MPG to the worst.

The best was “keeping to the speed limit”, the worst +10mph.

Thoughts: I found that whilst the majority of people “allowed” me to keep to the speed limit there were a few who were real prats. One was a BUS driver in Greenford, who tailgated me at night with headlights on full beam.

A lot of people appeared to speed up to me, then slowed down and kept a good distance and lowered there speed to mine (usually on 30mph roads).

I found that generally tyre pressure did not effect MPG, though some books seemed to suggest it would. The best I got was 39MPG the worst 34MPG. (Vauxhall figures were not too far off 44MPG@56, 35MPG@75) Parkers get a lot closer to these figures though !

However the car is very under powered and I think the 1.6 version in the same body would give better MPG, especially as I do mainly motorway driving. I think the idea is that the more your foot is down more petrol you are burning, even though you may get there quicker, it still does not save you.

I think a good medium is not over revving the engine and keeping to a maximum of 3000RPM.

Oh yeah average costs of running the car was £5/day £25/week (petrol)

My Wife's Avalon has a control system that monitors avg Mileage, trip times, etc. Driving across Arizona, I was able to do some of those types of tests, and will confirm your findings. 80mph yielded a best of about 27mpg, while 70mph would do just over 30mpg.

I found it interesting that using the Cruise Control would give me about 1mpg improvement, even though I thought I was light on the pedal.

I would think tire pressures below 24psi would cut into mileage significantly.