Shut off TCS for a day!

This is one interesting topic. We need more scientific testing.
Maybe the tires are bold, which slip more on acceleration that requires intervention from TCS.

I tested it myself yesterday with TCS off ('16 Mazda6).
Honestly, I did not feel a difference. (yes, not scientific either)
My tires are fairly new.
Our 2016 CX-5 AWD has a set of brand new Radar Dimax AS-8 225/55R19 103V tires.

The key is even my wife who doesn’t care much about cars can immediately feel the difference, and is willing to listen to my suggestion turning off the TCS each time she drives because the CX-5 feels peppier with TCS off.
 
I would caution that the MPG meter on the vehicle can be quite inaccurate. Resetting it mid-tank could give you a bad indication. I've had the meter give a spot-on reading on one tank, overstate by 2 MPGs on another, when doing manual calculations.

I don't rule out that switching off TCS will improve gas mileage or provide smoother shifting. I'll try it myself at some point if I can remember to turn it off consistently. But you have to be a little more scientific about it for a firm conclusion.

Step 1: Fill the tank until the pump shuts off. Do not top off past that point. Reset the trip odometer to zero.
Step 2: Drive with TCS on until the next fill up to get a baseline.
Step 3: Fill up at the same pump as before, again not topping off past auto shut off. For those who are in the habit of topping off I'm sure you've experienced one pump allowing an extra half gallon or more while another pump will allow hardly any additional.
Step 4: Manually calculate the MPGs for that TSC-on tank. Don't rely on the MPG meter. Reset the trip odometer.
Step 5: Drive on that second tank with TSC off under the same mix of city, suburban, highway. Somebody suggested a Post-It note as reminder to turn it back on with each start-up,
Step 6: Return to that same pump again and do not top off.
Step 7: Manually calculate the MPGs on that second tank and compare to the first.

That should eliminate most of the misleading variables.
We're talking about the 'this trip' mpg reading on the main screen, not the avg vehicle mpg.
My commute last night with TCS on this time avg'd 32.9 mpg, so the mileage increase is holding (I had never seen over 30mpg). I'm guessing that this has to do with the PCM programming adjusting/resetting after running with TCS off (kind of like the effects of doing a couple of Italian tune-ups)
 
We're talking about the 'this trip' mpg reading on the main screen, not the avg vehicle mpg.
My commute last night with TCS on this time avg'd 32.9 mpg, so the mileage increase is holding (I had never seen over 30mpg). I'm guessing that this has to do with the PCM programming adjusting/resetting after running with TCS off (kind of like the effects of doing a couple of Italian tune-ups)
I knew exactly what you were talking about.
 
Ive driven with the TCS off since day II. Each time i start the car it shows up disabled..
Really? With yellow TCS Off warning light on? What year and model of your CX-5?
 
I checked everytime the mpg from whatever the pcm is providing back to the intotainment (speedapp) and it seems accurate to me.
Its the avg one although there are one or two more mpg meters stats available.

I was thinking to update my PCM to the latest calibration file but with the TCS discovery dont see any need now.
for me the biggest benefit is that the car is more responsive.


example photo
180E2A70-95AB-4D6B-8098-8136359DEB95.jpeg
 
You guys have me ready to turn off my TCS to see if I get the same results on my next rides. Mine gets good mpg as is, I will see if I notice a difference.
 
When I check the mpg per tank at every fill up, the meter is usually within .5-.75 mpg of the number I get from doing the math by hand
I think the onboard fuel economy reading should at least be consistent even if it doesn't match hand calculated results. So that should be a good way to make comparisons.

Hand calculations are subject to some possible inaccuracy. The pump could be wrong, the auto shut off isn't necessarily consistent in filling the tank to the exact level, etc.
 
Last edited:
IMO the reason why turning the TCS off affects the gas mileage is because the TCS uses brakes to control the traction of each wheel. The software may intervene the driving with brakes a bit too much without driver’s notice, and thus reduced the gas mileage. And I imagine turning the TCS off could extend the service life of brake pads too.

BTW, wife also said she could certainly feel our CX-5 AWD is peppier and more powerful with the TCS off, in addition to pretty significant MPG gain in stop-and-go traffic. With gas price keeps rising, $3.08 / gal. on Shell regular in our area, I was surprised to hear she said she’ll try to remember pressing the “TCS Off” button each time she drives the CX-5, just for better gas mileage ⋯ :whistle:
Sorry but I don't buy this explanation. The roads here have been perfectly dry for a while and I haven't driven in any conditions that would cause the TCS to see any wheel slippage.

I drove about 50 miles yesterday after filling the tank. I turned TCS off each time after starting the CX. I noticed no difference in drivability or in fuel economy. I know that this isn't a real test but that's what I saw from my car.
 
People are using the term 'lugging'. Do you mean not actually mean running in to high a gear so the engine is lugging? Or are you using that term to describe random gear shift changes?
I can't speak for anybody else, but to me lugging has always meant being in too high a gear just as in a manual trans when failing to downshift to the proper gear.

Before having TSB 05-002/20 applied, I would most often and routinely encounter it in turns, especially right turns--brake going into the turn. RPMs drop, then lug as I accelerate out of the turn. Also from a stop at a traffic light where accelerating then letting off the gas when realizing the guy in front is lollygagging, then reaccelerating. In short, 2nd. gear failing to drop to 1st. or 3rd. gear failing to drop to second.

That's in routine driving. In sport mode, or just zoom-zooming around, the RPMs wouldn't drop low enough to get the lug.

This was my #1 issue with the vehicle without a close second. Given the number of posts I've made on the subject you can it is my #1 obsession. The TSB has all but eliminated the lugs even though the TSB description does not address this problem.

My experience seems somewhat unique among normally aspirated 2.5L owners. I think more folks have complained about jolts into gear than lugs and some who have had the TSB applied see no difference. This is hard to account for. Perhaps the TSB is a patch not a re-flash of the entire PCM with different years or AWD vs. FWD having different base code. Or the performance adjustments that are stored don't get cleared out when the software update is applied. Or maybe the dealer blew it off in some cases--they probably don't make any money doing TSBs.

It occurs to me now that if the TSB doesn't yield any difference, maybe disconnecting and reconnecting the battery might do some good--just a wild guess not knowing what the TSB does or the procedure for applying it.
 
Last edited by a moderator:
Sorry but I don't buy this explanation. The roads here have been perfectly dry for a while and I haven't driven in any conditions that would cause the TCS to see any wheel slippage.

I drove about 50 miles yesterday after filling the tank. I turned TCS off each time after starting the CX. I noticed no difference in drivability or in fuel economy. I know that this isn't a real test but that's what I saw from my car.
What I meant is the TCS software isn’t perfect enough and sometimes activates “unnecessary” brake intervention in certain conditions even thought there’s no actual wheel slippage. This definitely will affect the MPG and brake life. The fact is our CX-5 AWD does result a significant MPG gain by turning the TCS off in last 2 days, no matter what the reason is, I’ll keep the TCS off as much as I can when the road condition is good to save some gas money when the gas price is getting close to the all time high.

I haven’t had a chance to drive our CX-5 as wife’s company has requested all employees are back to work daily like before the pandemic. But yesterday the second day she got 26.8 mpg for the whole day’s stop-and-go driving, and sometimes she forgot to turn the TCS off going out for lunch. Like I said, usually our CX-5 AWD gets 24 ~ 25 mpg consistently but now there’s at least 10% MPG gain based on computer calculation with TCS off most of time as she sometimes forgot to press the TCS button. She still felt the CX-5 is a bit more powerful, but she couldn’t tell if the shifting is better as our transmission usually shifts fine with no issues.
 
What I meant is the TCS software isn’t perfect enough and sometimes activates “unnecessary” brake intervention in certain conditions even thought there’s no actual wheel slippage.
If this MPG savings is real and not an aberration in the MPG meter when resetting mid-tank, which I would not rule out, that would be the most plausible explanation.

If real, you might say the TCS is too perfect, detecting minute slippages that the driver does not detect with tiny adjustments made in tiny fractions of a second. It could be constant, in every turn you make even on perfectly dry and smooth roads. That would certainly account for excessive brake wear.
 
Probably unrelated, but what bothers me is relatively hard downshift at slower speeds. and the accompanying engine braking
 
Probably unrelated, but what bothers me is relatively hard downshift at slower speeds. and the accompanying engine braking
Sounds like just the opposite of lugging. Then again, yours is the turbo--whole different animal, different torque curve, more HP, different system programming, whatnot. The TSB I referenced only applies to the normally aspirated 2.5L with cylinder deactivation.
 
OK, so here's a quick unscientific TCS-off test.

Left the house with 3/4 tank with the MPG meter having been reset at the last fill-up. It was reading 28.6 MPG and I left it as is.

Drove 10 miles to Home Depot with TCS off, about 4 miles on surface roads at 40-60 MPH, and about 6 miles on expressway getting up to 70 MPH. The reading dropped to 28.1 on that leg. That's with one stop sign and three traffic light stops

On the return trip with TCS on I took all surface roads with four stops for lights, about 1/2 the distance at 40-45 MPH and 1/2 at 55-60 MPH, again not resetting the MPG meter. The reading went up to 28.3 MPG as I arrived home.

In my case this suggests (1) the same or worse MPGs with TCS off or (2) the MPG meter is unreliable over short runs which I would not rule out.

I detected no difference in the car's feel or handling with TCS off on this dry day but I was not driving aggressively so how it handles ripping a turn would be a test for another day.

I won't draw any firm conclusions unless and until I run a couple of tanks following the procedure in post #17 above. I've got a rain/snow mix in the near-term forecast so that might not happen for quite a while.
 
Last edited by a moderator:
I think the onboard fuel economy reading should at least be consistent even if it doesn't match hand calculated results. So that should be a good way to make comparisons.

Hand calculations are subject to some possible inaccuracy. The pump could be wrong, the auto shut off isn't necessarily consistent in filling the tank to the exact level, etc.
“Should be” and reality are two different things. I check my mileage “by hand” at every fillup, and compare that value to the onboard reading. Sometimes they are within 0.3 mpg of each other, but more often than not they are off by 1.0 to 2.0 mpg - sometimes one is higher, sometimes the other is higher. Apparently the onboard is used to calculate DTE rather than the overall mileage between resets.

BTW I almost always use the same pump at the same station and when the pump shuts off that’s all that goes in. That’s as close as possible without actually measuring the amount it takes to fill the tank.…but even then how do you fill to the same place in the neck each time…
 
It is hard to get an exact test because of so many variables, even the amount of weight of the gas as it is used up. The car would have to be fully warmed up, and drive a loop with no stop lights. Maybe a 10 mile loop. I didn't have to drive my car today.
 
Back