toyota hilux 3.0 5l diesel revs and fuel economy

[leshby]

Hello I had a toyota hilux ln167r 4x4 dual cab diesel 3.0 5l with turbo fitted. My fuel economy is really bad. I have only had this vehicle for 6 months and am learning about diesels. When driving at 100 km/h the engine is reving at 3000 rpm. Which i consider to be high. It sounds like its working to hard. The tyres on the car are 31 x 10.5 r15 lt. The speedo seems to be 5 kms over at 100. So when doing 100 kmh im doing 105 kms . Is there anything i can do or change to bring the revs down and conserve fuel.

[Manxman]

It's 4WD ute - they're normally undergeared in top so they can haul loads. Gearing sounds about right. You should be able to get abt 10km/l if you're gentle & empty at that speed. My asprirated 5L did it constantly. (LN147R 4x2) Be careful, the 5L is not often turboed because it's too close to the thermal limitations of the iron head - overheating if driven too hard, is just too easy to do. You would benefit from good extra gauges if you watched them intelligently. BTW there's nothing else particularly better in that price range/year. Be content, don't flog it along, do the maintenance on time and it will be fine. As a rough guide, you will produce about 3.3KW/Liter/hr with an average diesel. Petrol engines cannot get anywhere near that. They do have more total KW, but lack the low speed torque of a diesel. Also, running your motor beyond abt 2500rpm invites fuel wastage, as the fuel doesn't all burn before the ehaust valve opens. this is normal diesel behaviour, hi speed diesels (>2000rpm) lose fuel efficiency as rpm gets greater than that. The 5L will take 4500rpm, but it would have terrible mileage up there.

Edited September 14, 2015 by Manxman

[leshby]

Hey manxman. Is the rev range correct. I presumed it would b lower. Is the tire sizes ok. Is there anything i can do to reduce the fuel consumption. I am having the turbo housing and exhaust manafold ant part of exhaust to next joint ceramic coated to cut down heat.

[Manxman]

The only things you can do are to slow down, and improve aerodynamics - Over diameter wheels are prob illegal. Maintain tyre pressures on the high side - but watch the wear pattern. Drive gently, partic in traffic or suburbs. Changing diff ratios is not easy, and is expensive. Keep coaster hubs on freewheel but engage 4WD at least monthly for 0.5 km to keep the seals lubricated. If automatic, it's almost a lost cause - as torque converter slip is always going to kill your economy. Keep vehicle as empty as possible, keep windows up at speed, use aircon sparingly.