MPG mystery solved, replaced by TPM mystery - Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum
User Tag List

 
LinkBack Thread Tools
post #1 of 4 (permalink) Old 12-08-2013, 09:28 PM Thread Starter
Learners License
 
Join Date: Aug 2013
Location: Westwood, Ma
Posts: 33
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Thanks: 1
Thanked 9 Times in 6 Posts
Groans: 0
Groaned at 0 Times in 0 Posts
iTrader: 0 reviews
MPG mystery solved, replaced by TPM mystery

I had my oil changed and tires rotated at the dealer 10 days ago. Then I noticed a drop off in MPG. I checked the tire pressures today (I usually run 40psi front and 38psi rear) and the techs were smart enough to adjust the pressure after rotation. But they were now 30psi at all four wheels, not the proper 35psi spec on the door jamb and manual. No big deal, it happens. So I added 10psi to the front and 8psi to the rears but I forgot to reset the TPM button. I've been driving around all day (75+ miles) before remembering my failure to reset the TPM, yet NO warning light on the dash after this considerable differential in pressures. Does the monitor only detect decreases in pressure or what? Just wondering.
Westwood1 is offline  
Sponsored Links
Advertisement
 
post #2 of 4 (permalink) Old 12-08-2013, 09:39 PM
Registered User
 
tickerguy's Avatar
 
Join Date: Nov 2013
Posts: 2,205
Mentioned: 87 Post(s)
Tagged: 0 Thread(s)
Quoted: 772 Post(s)
Thanks: 18
Thanked 481 Times in 361 Posts
Groans: 4
Groaned at 6 Times in 6 Posts
iTrader: 0 reviews
My understanding is that it's an indirect system (it works off the wheel sensors for ABS/TC rather than an absolute pressure transmitter in the wheel) so it will only detect differences between wheels. If the delta between where they were and where they are now was the same in all four or close to it the TPMS may not detect that.

BTW the indirect systems may not be as sensitive as the direct ones but IMHO they're superior because you do not have a consumable item (the sending unit) in each wheel which WILL require replacement and can require it at a time not coincident with a tire replacement as well, necessitating not only the expense but also the dismounting of tires when that would otherwise not be required.
tickerguy is online now  
The Following User Says Thank You to tickerguy For This Useful Post:
Westwood1 (12-09-2013)
post #3 of 4 (permalink) Old 12-09-2013, 01:20 AM
Registered User
 
Join Date: Jun 2013
Location: Boca Raton, FL
Posts: 175
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Thanks: 6
Thanked 18 Times in 15 Posts
Groans: 0
Groaned at 0 Times in 0 Posts
iTrader: 0 reviews
I've been driving around with my front right tire that has a nail in it and is leaking very slowly, so everyday I have to put air in it because the light keeps coming up. I'm putting off getting a tire because I just ordered rims and I'm trading this car in soon for a GT. But as far I know most of the time my tire pressure is between 20-30 and my MPG stays around 29 and has since I got the car
Beachhz is offline  
Sponsored Links
Advertisement
 
post #4 of 4 (permalink) Old 12-09-2013, 05:04 AM Thread Starter
Learners License
 
Join Date: Aug 2013
Location: Westwood, Ma
Posts: 33
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Thanks: 1
Thanked 9 Times in 6 Posts
Groans: 0
Groaned at 0 Times in 0 Posts
iTrader: 0 reviews
tickerguy, I agree that it is a superior system for the reasons you stated. I guess the 2psi difference in the rear was to small to detect (while I was thinking that the 8 and 10 psi difference was too large to ignore). Thanks.
Beachhz, I suspect that it would take more than one low tire to affect MPG. We had a three legged dog once that ran pretty darn fast too but he didn't have to eat any extra to do it.
Westwood1 is offline  
Sponsored Links
Advertisement
 
 

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mazda 6 Forums : Mazda 6 Forum / Mazda Atenza Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome