Anecdotal: No real data or statistics other than 60k mile of personal experience with a 5sp inline VW powered 2wd. I always get better gas mileage when I run at a higher RPM and a lower gear unless I am running on a freeway at a sustained speed that demands top gear.......When I do extended logging road cruising or off road backroads, or even go through the mountains at high elevations, I normally gear down and run my ABA 2.0 liter motor at around 3500rpms in whatever gear gives me a reasonably safe speed...without lugging the motor. If my rpms drop to below about 2800rpm, I select my next lower gear, or when I come to a corner or a hill that I know will slow me dramatically on exit...I shift down, rather than waiting till I 'find it won't maintain speed' and then shift down. I think keeping in the range of rpms where the engineers designed the motor to make it's best power, that is where you will be most economical with fuel consumption. I understand the WBX motor was designed to run at lower rpms....so I am sure it works better there..the inline VW I have seems to be best between 3500 and 4500...maybe 5000, so that is where I drive it and my gas consumption goes down if I let the revs fall... And as Frank said, lugging a small engine with a big load is NOT a good plan unless it was built to do that, and Jetta motors were not. Don Hanson |
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