Thread: 3.9 v8 fuel economy

Originally Posted by 7knightsfishing

Totally untrue sorry. I have had heaps of V8s. Holden and Chev and all much bigger and chew less fuel. They had more balls too.

You might have to qualify that a bit. We don't know what was untrue or what your holden/chev V8's were in.

There have been plenty of threads on 4wd forums about how good on fuel V8 commodores are compared to Range Rovers.

On the topic of 3.9 V8's, I'm tuning mine and having good results. It's stable cruising at AF of 15.5, I'll see if I can push that higher. No fuel economy results yet, I'm still not through the first tank, but I've already got further than previous tanks.

O2 sensors are a good thing, but using them will clamp the tune to stoich in normal running. Tuning without you can go leaner at low load and gain some extra fuel economy.

A small capacity V8 in a heavy 4wd with the aerodynamics of a brick of course will use more fuel than a larger engine in a lighter car that is under stressed and has a higher final drive gear.

just a note, someone mentioned tyre size and their speedo; I'm running 275/70/16's under my 93/4 disco and according to the gps the speedo is bloody accurate.

one of the problems the 3.5 through to 4.6 is the head design, compared to a modern LS Chev head they are very ordinary, you can get hotshot heads but they are extraordinarily prohibitively expensive.

cheaper to do a LS conversion but then you have all the associated issues with the extra power

Wow 43 replies no make that 44 replies for the same old chestnut……….Time to accept the fact that these things were horrendously thirsty from the moment they left the factory.
But that said I still wouldn't part with it.

Originally Posted by 98discovery

Wow 43 replies no make that 44 replies for the same old chestnut……….Time to accept the fact that these things were horrendously thirsty from the moment they left the factory.
But that said I still wouldn't part with it.

But you can now tune them from horrendously thirsty to moderately thirsty.

Haha. Very well said from a non owner. Done all that and still dirty on the Disco.

Soon my wife and I will be off around Oz for a year or so. Her indoors wants a van with shower/toilet so 2.2 tonnes ish is what we'll be towing. I currently have a 97 3.9 manual with 200k on the clock. Mechanically it's all good, has all the necessary extras, and sounds great. Over the course of a year the extra fuel bill will be 5-7k ish, depending on km traveled. I have tried doing an exercise based on trading to a TD5 but will I come out better keeping the v8, after depreciation, elec brakes or whatever else such as changeover costs.

Question is: is the TD5 an altogether better car?

Originally Posted by 98discovery

Time to accept the fact that these things were horrendously thirsty from the moment they left the factory.

They were never horrendously thirsty - about right for a small V8 in a 4wd. The Nissan and Toyota petrol equivalents of the time were even more thirsty and many 2wds were as thirsty as the V8 Disco.

Yes they were thirsty compared to diesels but as far as petrols go they were not too bad.

They were never horrendously thirsty from the factory.

Garry