simonwref Posted February 6, 2011 Report Share Posted February 6, 2011 (edited) i was driving on an a road this morning, that switched between 30mph towns and nolimit sections. i was tired and driving lazy, so didnt bother changing down from 5th gear for the 30s. car coped fine and revs were just below 2k. got me thinking: is there a direct link between revs and fuel usage or is it more complicated than that? and therefore, can you make fuel last a bit longer by driving in a gear higher than necessary? Edited February 6, 2011 by simonwref Link to comment Share on other sites More sharing options...
londonlee Posted February 6, 2011 Report Share Posted February 6, 2011 i was driving on an a road this morning, that switched between 30mph towns and nolimit sections.i was tired and driving lazy, so didnt bother changing down from 5th gear for the 30s. car coped fine and revs were just below 2k. got me thinking: is there a direct link between revs and fuel usage or is it more complicated than that? and therefore, can you make fuel last a bit longer by driving in a gear higher than necessary? Yer as far as I no it does save a bit extra fuel I do that most of the time when I'm really trying to save the petrol I drop it in to 6th around 35 and it seems to make a fair difference but its boring as hell lol Link to comment Share on other sites More sharing options...
Bek8111 Posted February 6, 2011 Report Share Posted February 6, 2011 Was always told keep the revs under 3k and you'll save fuel... Easy enough when cruising, as 3k in top seems to be 75 mph in most cars Link to comment Share on other sites More sharing options...
crewcutchuck Posted February 6, 2011 Report Share Posted February 6, 2011 As long as your not making the engine labour too much. Its how well the engine burns the fuel that also needs to be taken into account. If your going uphill at 30mph in 5th you might have a lot more throttle on than if you were in 4th. That's what I find when I do my little mpg tests. As long as your not making the engine labour too much. Its how well the engine burns the fuel that also needs to be taken into account. If your going uphill at 30mph in 5th you might have a lot more throttle on than if you were in 4th. That's what I find when I do my little mpg tests. Link to comment Share on other sites More sharing options...
silver gt Posted February 7, 2011 Report Share Posted February 7, 2011 In simple terms, the amount of fuel burnt is a function of engine revs and throttle position. At full throttle you are using twice as much fuel at 6k revs as you would at 3k revs. For best fuel economy you need to be in the highest gear possible, but not labouring. Link to comment Share on other sites More sharing options...
dublet Posted February 7, 2011 Report Share Posted February 7, 2011 Also depends on the amount of hills. Whenever I do a run to the Netherlands, I'm surprised at the mileage I can get from Calais to the Netherlands, averaged about 60mpg in my Avensis Diesel. Link to comment Share on other sites More sharing options...
gareth123 Posted February 7, 2011 Report Share Posted February 7, 2011 Does anyone ever take much notice of the little fuel economy indicator lights (presumably they are standard on all Gen 5's)? They seem to pretty much back up what has been said on here so far. Link to comment Share on other sites More sharing options...
Alan Clogwyn Posted February 7, 2011 Report Share Posted February 7, 2011 Does anyone ever take much notice of the little fuel economy indicator lights (presumably they are standard on all Gen 5's)? They seem to pretty much back up what has been said on here so far. That must be a French thing, UK and jap cars don't have them. Using the engine under least load will improve your fuel economy, you need to trade that off with revs. In a flat 30mph zone you'll get better mpg from being in 5th and just letting it cruise along than having it in 3rd with your foot on the throttle a bit. Hoever if you're going uphill you'll be better off in 3rd with your foot a little on the throttle than in 5th with your foot a lot on the throttle trying to keep it from stalling. Link to comment Share on other sites More sharing options...
dublet Posted February 7, 2011 Report Share Posted February 7, 2011 That must be a French thing, UK and jap cars don't have them. My Dutch one had them too. It was hilarious, basically it just went to orange every time you mashed the throttle. Well duh! Link to comment Share on other sites More sharing options...
KrisSilver Posted February 7, 2011 Report Share Posted February 7, 2011 I heard you should always try and stick to between 2-3k. So from that I deduce if I'm below 2k I change gear to keep it literally just at 2k. The car does slightly labour harder when going below 2k too I find. Link to comment Share on other sites More sharing options...
Angus Posted February 7, 2011 Report Share Posted February 7, 2011 Got one of those mpg needle things in the BMW (never had one on any Gen 5 I had) ... light pressure on the throttle and it drops to 12mpg easily, floor it and it immediately goes off the scale past Zero. Angus Link to comment Share on other sites More sharing options...
gareth123 Posted February 7, 2011 Report Share Posted February 7, 2011 For those of you who haven't seen them, here are the economy lights on the rev counter. I assumed they were universal - obviously not. I do sometimes try to drive by them if I am low on fuel - and yes sometimes it is the labouring in a higher gear rather than revving in a lower one that drinks more fuel. Link to comment Share on other sites More sharing options...
sbdags Posted February 7, 2011 Report Share Posted February 7, 2011 In simple terms, the amount of fuel burnt is a function of engine revs and throttle position.At full throttle you are using twice as much fuel at 6k revs as you would at 3k revs. For best fuel economy you need to be in the highest gear possible, but not labouring. This is spot on! something like 56mph in 5th (in the gen 5 & 6 anyway) is the most fuel efficient. And that's about 2800 rpm and not labouring the engine. Link to comment Share on other sites More sharing options...
Recommended Posts