what's the optimum cruising speed for diesel pickup

[kurt]

hi,

i have read the "ginagalit ang makina" thread and its has brought up a few questions in me

my ride is a dmax 4x2 MT i now shift-up normally at 2.2k rpm as the top torque is reached at 2k rpm. before at least 1.5k rpm pwede na. city driving , my crusing speed is mostly at 80kph-- 2k rpm

when i drive at nlex now, i shift-up at 2.5krpm. and a lot of times when overtaking in provincial roads i shift at 3k rpm or more. and my criusing speed is at 100kph-- 2.5k rpm. but the last 3 mos i always get the urge to speed up upto 130kph running at over 3k rpm (with more power to give) upto Sn. fernando exit.

question, is this the right driving technique to preserve the engine in the long term as against getting the best performance from the diesel engine. - protect it from smoke belching or similar symptoms of degraded performance -- after a couple of years?

is cruising at the engine speed with top torque (2k rpm in my case) the best technique to drive in terms of fuel economy and to preserve engine life/performance (with occasional runs on nlex at 100-130kph)

i believe putting oil that exceeeds manufacturer's specs is beneficial for the vehicle, like a ch4 grade oil, but i do not yet now what oil gencars use (i guess the grade is CD4 only but cannot guess the brand).

after the warranty i plan to always use the semi synthetic formula of petron. or can you please suggest other options. maybe a castrol or mobil brand.


thank you all.

[ian_rex]

sir, let me post my opinion.

first off, i too drive the same ride as yours. your question raised my interest. it is always depends on what is your objective. as far as i know the 4JH1-TC engine of the dmax is quite potent for a diesel engine. going back, when i said 'objective' i meant that what is your driving style. is it passive or aggresive driving.

passive driving leans more on fuel efficiency. thus if you drive efficiently, you should not exceed the 2000 rpm limit. i usually shift up when i reach the 1500 to 1750 rpm. and try to build and maintain the momentum until i reach 2000 rpm then no more. the fuel consumption using this technique yields to an average of 11 to 12 km/L on a combined traffic situation.

on the other hand, aggressive driving which i don't normally do (but could be when provoked and unleash when needed), if you are up for saving time, then the rpm should be no less than 2000 rpm, which i presume, revving up to the limit. but this not only increases your fuel consumption but also the risk of accident as well. besides, i don't want to push the engine so hard because i don't want to stand the chance for an earlier than usual engine overhaul. the worst fuel consumption i made is 9.5 km/L.

honestly, i still gotten used to the noise the diesel engine creates at mid and high rpm's.

also a piece of advice, if you are up to driving aggressively just don't push that accelerator instantly, the engine spews out a smoke regardless of the condition of your engine (which is i presume excellent). let the turbo work for you by gradually pressing down the accelerator pedal (about 3 seconds). once it gets spooling you'll get the results.

for the oils, semi-sythetics won't do harm. i'm even planning on changing to sythetic eventually.

thanks!

[ARB]

as long as you dont go over the redline any RPM is ok. just dont lug your engine its the worst you can do to it, its just like starting it cold in the morning and revving it up ang effect.

[mikey177]

... just dont lug your engine...

Pardon my ignorance, but what does "lug your engine" mean, or rather, how is it done?

[diesoline]

bro, lugging it means straining the engine -- usually happens when one uses too high a gear at lower speeds. eg., starting from a dead stop in 2nd gear or driving in 3rd too slowly that the engine starts to make struggling sounds.

[S-works]

optimum cruising speed would probably mean fast enough to get from A to B, without using too much fuel right? my guess for my own ride, in 5th gear w/ rpm around 2-2.5k rpm. speed around 80-100 kph would be just right. i notice higher fuel consumption when speeding at 110 and up, about 1-2 kms less per liter :-)

[quiksie]

theres no harm in making your engine galit, its a diesel anyway. Pag mas lower ang shifting mo, lets say mga 1500 yun rpm, would it affect the engine or build up any oil residues sa exhaust mo because of unburned diesel?

[mikey177]

bro, lugging it means straining the engine ...

Thanks, diesoline. Yun pala ang tawag dun.

[OTEP]

Usually (but not in every case), the optimum cruising speed is with the speedometer pointing straight up (whatever speed that is).

[empy]

as long as you dont go over the redline any RPM is ok.

yup, car engines are designed to operate for long periods of time at any rpm under the redline. however, for fuel efficiency and reduction of noise inside the cabin over long trips, many people choose to stay between 2-3k rpm.