Thread: Diesel Fuel consumption in Hot weather

The fuel expands in the heat so when you put it in your not getting what you pay for so that is a contributing factor! So when you fill up and then it cools it will appear that the consumption is up its not your just being ripped off best to fill up in the morning when the tanks are cool!!!

Cods-Wallop

I would have thought the hotter air is less dense so there is less oxygen per intake charge to help make a clean burn so if you get less power you use more fuel. But an intercooler should negate most of this problem.

Just a guess.

Actually, the time of day when you fill up has very little to do with the temperature of the fuel going into you tank.

The temperature of the fuel when it is delivered to the servo is what ultimately governs the temperature coming out of the underground tank, because the underground tank is naturally insulated, the fuel can remain at the same temperature for weeks at a time.

It is a common practice for the fuel companies to deliver “hot” fuel and this will be expanded over the same fuel at room temperature.

This problem is know but to date only South Australia actually regulates the delivery price based on the temperature of the fuel, by mandating that all road fuel tankers have temperature gauges fitted to the delivery line.

The only thing you can do is take note of how warm the fuel nozzle gets while you fill your vehicle.

The warmer the nozzle gets, the more you are being ripped off ( not that you can prove it )

Originally Posted by DirtyDawg

I have noticed the fuel consumption elevates slightly whilst driving in hot weather....is it a real usage or a sensor thing due to the heat?

I mate of mine drives trucks interstate,& he swears that driving in the cool of night decreases fuel usage.I think the cooler air is denser & increases the efficiency of the engine,particularlya diesel.Thats why a larger intercooler helps.

Umm,always wondered how the different manufacturers get their ratings for their engines,if temperatures make a difference,i bet they are not rated at a certain temperature of,say,intake air.....

Just my 2 cents worth....

I have noticed on really cool mornings that the vehicle feels better to drive. My mate in his 130 will drive it to work on cold morning rather then take his holden because he says it feels so much better.....

I am sure someone smarter than me could tell us the coefficient of expansion for diesel - I'm not convinced (yet) that it is significant for the temperature variations we are talking about.

My Td5 certainly goes better in the cold (below 13degrees C) - I assume it is the denser cold air.

Back to the original question - My first thought was Airconditioning?

Don’t have a trip comp on the TD5
but we have a VW golf 2.0TDi and the consumption will be up by as much as 20% on a hot day – I’ve noticed it starts to climb once ambient temp is over 27/28. Acording to the tech doco for the VW engines the ECU monitors inlet temp and will decrease turbo boost when the inlet temp passes a set mark. So not only is the air containing less O2 but the turbo is strangled back compounding the effect. It’s definitely Intake air…. And a larger intercooler would have to make a difference.

Most extreme case I've seen to date:- Travel from home to the Nerang (couple weekend ago) freeway all the way.
Trip down at 1:00pm 36deg – cruise set at 100 av 5.4L/100
Return Trip (same load) at 1:00am 24deg – cruise set at 100 av 4.3L/100

AirCon would be contributing to some of that but not 20%. Figures we have noticed showed AC on (compared to off) adds about 0.2/0.3 and yes It uses more with AC on and windows up then AC off and windows down (another myth)