When i bought by truck i was told by the previous owner that keeping overdrive on permanently,even for short trips around town would help economy by about 3mpg?
A work collegue stated the opposite - that the engine will labour more at low revs and work harder,any thoughts please?
if you have an autobox overdrive is supposed to be on ALL THE TIME....no question. Otherwise your normal gears are overworked, the vehicles revs too high all the time and the fuel consumption will be appalling.
The only reason to EVER keep O/D off is if you are towing a load up a long slow hill and want to keep the revs and torque up by staying in a lower gear....anyone who leaves it off in normal conditions needs their head examined....the only other reason is if you either want to get a heavy load started, or to accelerate away more briskly, in which case you floor it with O/D off, then flick the switch once it gets up to a reasonable rate of knots...in fact on the T2, if you set the gearbox mode to Sport (or Power on an older Mistral?) and O/D off, acceleration is noticeably faster, but uses a lot more revs and therefore fuel!
Your work colleague is wrong, all O/D does is ADD intermediate gears, so it still uses the original 2-3 gears, or whatever the box has as basic, then adds another cog on top of some or all of them.....so as the car accelerates it goes through ALL of the gears, NOT just the ones added by having O/D...so no labouring etc..
Older boxes would have had just O/D on top gear in some cases, but modern boxes use O/D on all the gears as far as I know, with the possible exception of first, so the T2 auto box has five effective gears from the basic three in the box.
I'll give her a good lube first then:naughty
