Does shifting at low RPMs really hurt the engine?
 

Hi guys, i have an AT and my daily drive is PURE traffic. My "average speed" reading on the gauge is usually just around 20kph.

So i tried experimenting on different shift styles, shift points, sport mode D on off etc, and such and the most significantly economical fuel saving i get is driving this way -

(1) featherlight throttle - never past 1600 rpm (unless uphill i let it go 2000, you can feel it anyway when the car needs more)
(2) driven in M mode - I shift when the arrow comes up which i recorded to be at 13kph to 2nd, 27.5kph to 3rd, 38kph to 4th, and 52kph to 5th. (i never reach 6th because of traffic)

Result, I normally get 15L/100km instead of the usual 18. So i get to travel about 260km before fuellin up rather than 215km.

Q.. i dont really "feel" the engine lugging, and if it DOES lug, like when going uphill, i give it more gas and let it hit 2k rpm. Point is i just accelerate really slow since its traffic anyway.

Is this in anyway "bad" for the engine or transmission long-term? Because i noticed my manual shift points are even earlier than D with sport mode off and an eased throttle.

Why is your fuel consumption so high? My BRZ is manual, but my Forester is auto and I usually get 11-11.5L/100km in PURE traffic.

About shifting points, I would just leave it in the D mode.

Shifting at low RPM in and of itself isn't bad for anything. The only thing bad in what you describe would be if you are lugging the engine at low RPM (basically below 2k). However, if you're very gentle on the throttle at those low RPMs, then that isn't an issue either. In heavy traffic, I often keep the car in 2nd, which has the engine well below 2k RPM, but it is either just idling along, or I'm using light throttle, so it doesn't matter.

Low RPMs aren't bad for anything. Lugging the engine at low RPMs is.

Also does 15L/100km really translate to 15 MPG (US)? If so, something is horribly wrong with your car. I can't even get that low mileage in a day of autocrossing and towing a tire trailer. You should be getting closer to 25 MPG (10L/100km) in traffic, especially in how you're trying to drive efficiently.

How are you calculating that mileage? I can not imagine any possible way to get that bad even in traffic. Fuel would almost have to be pissing out.

I get 28.3mpg (according to the gauge) in stop and go. Takes 1 hour to go 22 miles to work and an hour to go 22 miles home. That translates to 8.311469 L/100KM.

Unless he is checking instant mileage consumption and not average ...

That is why I asked where he is calculating it. Wouldn't be the first to do that.

If you have an auto why are you trying to manual shift it. Just let the car do the work. Else buy a stick shift.

I had a Honda accord. Drove in traffic a lot and idled it a lot to charge phone or run heat/air con. Averaged 19-20 MPG in it. On highway trips though it will easily hit 35 mpg.

I wouldn't worry about shit MPG in poor driving conditions with a lot of idling...

Actually I just did a few trips in my BRZ and getting around 32 mpg doing 70-80 on the highway. But my "average" is 17mpg.

Hi guys, thanks for the input on as long as acceleration is gentle (not lugging) that definitely helped as thats what I do.


And to those who ask about mileage, the local version of our car comes in kph and L/100km in the indicator (not mpg). translated to KM/Liter, I get about 5.6-6.2.
Similar to our yaris and even our 1998 land cruiser lol!

I dont think you guys have the same understanding of traffic as we do in the Philippines. Check out "Philippine traffic" on youtube. We dont stop and go. We just pretty much STOP 90% of the time and crawl to a go. There is no GO. theres just stop and crawl.

The literal crawl and go traffic in my country (philippines) begged for an auto.. :) I never hit the highway too

yeah i am super gentle with the accelerator and would also do the same 2nd gear you do :) thank you for the answer! yes 15l/100km translates to 15.6 mpg :)

couldnt the type of gas being used cause the more frequent fill ups and bad mileage? but that being said i have an AT as well and just leave it in AT when driving, i dont find the need to be in its "manual" mode and especially in the city where its stop and going but thats just me. i also average 600km a tank

exactly tcoat! take a look at philippine traffic on youtube. thats literally 99% of the road i commute in everyday. no freeways/highways too. :)

Don't lug the engine.

https://www.youtube.com/watch?v=soJe...ature=youtu.be

Basically, you have a slow moving piston but a fast and power explosion. That force of combustion has to go somewhere. You want it going to the wheels, but lugging results in combustion that can't effectively push down the piston and you just waste fuel and wear the engine.

Besides, the optimal operating range for our engine is somewhere in the 2,500~3,000 range, right? It sure seems that ways to me. If you're doing anything other than coasting on flat ground, I'd downshift and keep it over 2,000 until you want to coast again, then go to the highest gear.