Club 80-90 Forums

i have a ej20 in a caravelle...just got back from a cornwall trip - i think i was gettin about 90miles to quarter of a tank, but who knows with the dodgy fuel gauge!

Anyone know a better technique to work out my mpg?

What is everyone else getting with a subaru conversion?

Better? I couldn't think of a worse way

Just do this: it's the only way:

Always top the tank to the same point, usually the best and most reliable point is the first click of the nozzle. Whilst it doesn't really matter in the long term, its best for fill-to-fill figures to do this at the same station, same pump, holding at same angle - but just top it -

And at each topping record the mileage. Actually get a litres VAT receipt and write it on it, every time.
Thats all...
Then its easy, just keep plotting topup-to-topup miles divided by gallons to fill (.22 gallons = 1 litre) - this represents the mpg for the drive before the fillup. The first top-up of course you can't get a figure - and that's one way peeps kid themselves, they start with a false datum.

Doesn't matter when you topup, even 10 miles down the road from the last one, you just get a more frequent check of mpg. But it must be brim-to-brim, and don't draw ANY conclusions until you've done at least three or four on the trot, back to back. And don't try to do mpg per tank, that's another way peeps deceive themselves, a contents gauge is as good as useless when it comes to mpg accuracy

Best is to plot them on graph paper or in Excel, as you'lls ee where you've made a mistake or things going wrong with driving, engine straight away.

Oh! And don't EVER believe the mpg that anyone tells you they're getting - EVER!

... unless you see the data above for each and every fillup for about a year! And plot it out yourself

To give this sort of result in Excel or on graph paper



I have rarely seen the mpg-to-date curve go up, but it should stabilise after a few months or so of typical driving. By looking at both curves in relation to weather, driving style, type of journey and load its quite easy to spot when something is going amiss with the vehicle, performance wise.
Over a year or more you'll see a seasonal trend, down in the winter and up in the summer, maybe around 10% deviation.

Using the method above, it doesn't matter if your fills are inaccurate or you forget to write down the mileage of one or two occasionally - as long as you keep all the fule bills with the litres on them, and file them away in sequence. As long as you enter the fuel gone into the vehicle. If you don't fully fill it, then just make a note of that, but when you do, it'll bring the running mpg-to-date back to an accurate figure. Howevere, it is best to alwasy try to brim the tank to the same point if you want to see the fill-to-fill curve as meanignful right across the chart.
Don't use the trip, use the mileometer/odo to give a permamenet record of your vehicles consumption against its life mileage

Well I've just been to York and back did 330 miles in total and about 52 litres and it works out to be about 28.5 mpg, and the funny thing was on the A66 and the A1 I was cruising between 80 and 95 when I could.

I must also add that there is a very embarrased driver of a ZR that found it difficult to leave me

Forgot to mention this was in a EJ22

That's a very good figure, for a petrol. So presuming you brimmed it before and after, wait till you brim it again and clock the mileage again - that will be interesting to see and then after 2 or 3 more sets of figures where the trend is going. Happy to plot this out if you want to send the figures.

i nearly always get about 27mpg ,but i do have a heavy foot ,but thats drag racers for you

Heavy foot, light wallet Scoobs

klatuu wrote:on the A66 and the A1 I was cruising between 80 and 95 when I could.

iirc the A1 is littered with SPECS cameras isn't it

ill be getting more now the petrol isnt leaking out of the breather pipe!

What!!!!

I didn't notice any, oh well, If I get a number of tickets I'll just say I was speeding once.

my previous best was 320mls from a tank ,but just got 336mls towing a race car.but should be more cos i hadnt run out

ok so i should be able to get to cornwall on one tank..

at least that gives me a rough idea, thanks!

The consensus from every one of my customers with EJ22 and EJ20 2WD T25's who has given me feedback on mpg is between 27 and 30 on a long run on good roads.
My Syncro EJ25 does 23mpg on my b roads route to work at 30 - 60 mph, averaged over 500 miles of just driving to work and back. On the motorway it does 25 ish at 80-85 mph. The best I've had so far is 27mpg at constant 65mph, cruising to Bug Jam and back with mates in air cooled's, carrying all my kit and all the tents / beer, etc which they couldn't fit in, or was heavy enough to make their lowered KG's and Beetles rub tyres on the arches!
I've also found that the odometer is incredibly accurate - less than 5 miles out over a 400 mile journey accorging to AA route planner.

Hope that helps,

Richard, RJES

There ya go!

And a good allround average figure of 25 mpg seems like the one to use, as it fits quite well with a lot of Subaruvanagon data from the US, when they aren't talking about 2.5 ton vanagon campers!

Jeez... I really must find a way round these stupid laws in France....
I am sure there is one, but its finding it...