Thread: 93 petrol RR fuel economy

Originally Posted by Darryl Prizeman

Purchased the vehicle earlier this year and the fuel economy at present is about 20l/100k.

What should I expect?

About that much Best you may get is 13 or 14

Depends .. Country or City // 5 min drive or longer??

Try to drive after the temp gauge starts to move (register) rather than start then drive .... as the EFI is sending more fuel for cold running

If you want to improve it .. you will have to start looking at the condition of exhaust / EFI / etc

Apart from the usual myriad of factors influencing fuel economy such as engine tune, tyre pressures etc I found the following two bits of technical advice very useful for my 1990 RR with Lucas 14CUX Hotwire Fuel Injection.

1. There's a recessed hex head screw on the side of the air mass sensor (aka airflow meter in the older days) which adjusts the resistance of the electronic circuit that measures airflow. If the resistance is too high = whole fuel injection system runs too rich (usual symptoms are stumbling and spluttering when cold, exhaust popping or even detonation on a trailing throttle, black exhaust smoke and sooty spark plugs). I was told that the factory setting is around 280 Ohms but that turning the screw anticlockwise reduces resistance to achieve 80 - 100 Ohms - usually necessary to get exhaust CO levels within limits. Mine was over 400 Ohms and engine running very rich. Resistance is measured across the two outermost terminals on the multipin plug that plugs in to the side of the air mass sensor with the ignition OFF (just remove the multipin plug to access the pins with your multimeter probes).

2. Original Lucas fuel injectors are commonly basket cases, especially after 160,000 km. EFI specialists say they don't come good with cleaning and resetting and soon deteriorate again. Ford "Yellow Tops" injectors will fit straight in and cost me $440 incl GST for a reconditioned set from a local EFI specialist. There's lots of posts on this site and elsewhere about substitute injectors.

These two operations did by far the most to settle my EFI problems. It's also cheap and good practice to replace the EFI Engine Temperature Sensor - about $30 to $40 and five minutes work.

my 1993 does 5km to the litre on tank average driving expect 350km tops for 65 to 70 litres refill on the tank

I used to get 18mpg out of my 1994 3,9 vogue se back when I was in England. Think that works out a bit better than you are getting.

I would have thought 17 or 18 l/100km would be ok.

Have a search for threads by PhilipA in regards to his oxygen sensor install. I've done it and it certainly doesn't run rich anymore. Don't know fuel figures as I run LPG most of the time.

It has been just under 2 years since I first posted this item. Since then I have spent a reasonably amount of time and approx $2K in improving the economy of my Rangie. The best I have achieved is 13.6ltr/100k's over 500 odd K's all highway (Gympie to Rockhampton QLD) with 4 adults and our luggage. I consistently average in the low 14's for highway and high 16's around town.

What did I do:

The air flow sensor was faulty and thus replaced, improved the economy to 18/100 approx. The big saving came from fitting an adjustable fuel pressure regulator, the motor was running extremely rich. We also fitted new injectors from a Commodore, the advice I received on injectors was modern technology, better spay patern.


I am well pleased with the result.

Rangie's rule

Cheers all

I must say I only recently fitted an adjustable fuel pressure reg to my classic, and although I no longer have economy figures and the vehicle is far from standard, I did notice an improvement in fuel economy.

I done a trip to scenic rim prior to fitting the regulator, did some good wheelin, drove home, drove to work and back twice (only 3klm). Put 65 litres of fuel in (so had about 15L left).

Then I fitted the regulator, did another trip to scenic rim, drove harder tracks and more of a distance. Drove home, left the car parked out the side of the house for three days. I had 10L of fuel in the tank.

So I used more fuel on the second trip with the new regulator, BUT I put a crack in the tank about 5 minutes into the first hard track and it was leaking as fast as 3 drops a second at times. And the car sat leaking into a dirty old bucket for three days before I drained the tank

My RR Classic 1994 got 17-18 l/100kms ciy cycle and a bit better on the freeway. Gawd I loved that car wish she hadn't insisted on a new car...

Anyway, when talking of old Rangies the word "economy" is used becuase the money spent on fuel is enough to run the economy of a small pacific nation.