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.

[kurt]

ianrex- since we have the same ride, your data on fuel consumption is nearly identical to mine, on the average worst: =<9km/l, best =>12.5km/l (hiway drive only) but shifting on higher +300rpm mark. though on a trip to pagudpod when the dmax was 4mos old, i made a surprising 14.4km/l but i now could not duplicate it even when idrove to pagudpod another 3 times i recall =<13km/l ang best ko. i think i just had my PMS or the type of oil or fuel ???. previosly a shell fuels guy, now i believe the marketing crap of petron but my cars seems to agree.

s-works and quiksie - i do practice a combination of what you suggested .

otep - i checked my cars, oo nga sa speedometer, i think the crusing speed at top gear is located on 11 o.clock, 12o.clock or 1 o.clock position

[Raven]

Sir, base on my experience with turbodiesels (patrol and Strada), you should keep the rpm at at least 1800k to have decent 'shove' even on flat gradient. For good performance and economy, try keeping it below 2500k. If you drive aggressively, you should keep it between 2000k-3500k. Reving your engine to its redline occassionaly is also suggested to prevent deposits from building up.

[ian_rex]

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 :-)

sir, tama ka. normally mas matipid talaga sa range ng 80 to 100 km/h, at 70 km/h it is also efficient kaya lang mabagal, nakakabagot. another thing is, try to maintain a constant average speed. kung 80 km/h then that's it, hindi yung accelerate ka pa hanggang 100 then decelerate to 80 then accelerate ulit. malakas sa fuel consumption ang ganoong klase ng driving style.

[ian_rex]

ianrex- since we have the same ride, your data on fuel consumption is nearly identical to mine, on the average worst: =<9km/l, best =>12.5km/l (hiway drive only) but shifting on higher +300rpm mark. though on a trip to pagudpod when the dmax was 4mos old, i made a surprising 14.4km/l but i now could not duplicate it even when idrove to pagudpod another 3 times i recall =<13km/l ang best ko. i think i just had my PMS or the type of oil or fuel ???. previosly a shell fuels guy, now i believe the marketing crap of petron but my cars seems to agree.

s-works and quiksie - i do practice a combination of what you suggested .

otep - i checked my cars, oo nga sa speedometer, i think the crusing speed at top gear is located on 11 o.clock, 12o.clock or 1 o.clock position

sir kurt, haven't made my most fuel efficient as of this time except for 13.7 km/L in a combination of city and highway. could it be in consistency of driving style? teka sir, open ba yung bed mo? yung dmax kasi namin open, kaya ganun lang ang kaya. i figure i can squeeze out more kung mas efficient ang aerodynamics ko. hehe.

[kurt]

normally open nga but for vacations its loaded with stuff and covered with lawna. as for long distance driving style - cruise at 90 upto 120kph or upto 3k RPM depends upon the road conditions and aircon always on.

but happy na ko sa averages ko. its a non-crdi 3litre engine with a open box at the rear. i follow the innova thread and im happy that the dmax is still a contender for a fuel economy run.

many have suggested to install a bed cover to improve its aerodynamics to allow for better fuel economy. what i want is a clip.on or strap.on lawna (already seen one on the road so i plan to visit gandara st. in ongpin to look for one - lawna capital of metro.mla) since this is the best for my needs

or maybe a a color keyed campershell to try and mimic an alterra. joke seriously.

[mikey177]

...Reving your engine to its redline occassionaly is also suggested to prevent deposits from building up.

Is this safe? How many RPMs above the red line can you safely push a diesel engine? For how many seconds or minutes should this procedure be performed, and how often is "occasionally"?

[ian_rex]

sir mikey, pretty safe. basta wag mo lang biglain. build some momentum first. rip the rewards later. haven't tried pa pero ako kasi,basta na maxxed out ko na yung 100% hp, tinitigilan ko na.

[ian_rex]

normally open nga but for vacations its loaded with stuff and covered with lawna. as for long distance driving style - cruise at 90 upto 120kph or upto 3k RPM depends upon the road conditions and aircon always on.

but happy na ko sa averages ko. its a non-crdi 3litre engine with a open box at the rear. i follow the innova thread and im happy that the dmax is still a contender for a fuel economy run.

many have suggested to install a bed cover to improve its aerodynamics to allow for better fuel economy. what i want is a clip.on or strap.on lawna (already seen one on the road so i plan to visit gandara st. in ongpin to look for one - lawna capital of metro.mla) since this is the best for my needs

or maybe a a color keyed campershell to try and mimic an alterra. joke seriously.

sir, pa-post ng pic once you decided to install a lona. yun ba yung may velcro? i'm contemplating on having one. saka how much.

thanks!

[niky]

Is this safe? How many RPMs above the red line can you safely push a diesel engine? For how many seconds or minutes should this procedure be performed, and how often is "occasionally"?

Actually, 3.5k should be enough to do it. The idea of redlining is to fully lubricate the valve-system. Doesn't have to be more than once or twice a week.

[ian_rex]

Actually, 3.5k should be enough to do it. The idea of redlining is to fully lubricate the valve-system. Doesn't have to be more than once or twice a week.

acknowledged sir niky.